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All posts for the month January, 2015

Cuttlefish Robot! Quiet, Agile, and Efficient

Posted by Ketton (Team UV) on January 29, 2015
Posted in: Presentations. Tagged: , , , , , , , , , , . 3 Comments

Swiss Federal Institute of Technology Sepios robot. Photo Credit: engadget.com

Team UV is not the only one who has an interest in underwater technology!  The latest in underwater robotics has taken inspiration from the undulating motion of the cuttlefish, rather than conventional methods such as propellers and solid fins.  Previous attempts at fish like robotics have produced decent mimics of fish motion, however, they have always been rather limited in terms of agility and precision.  Researchers form Swiss Federal Institute of Technology (ETH) in Zurich are set to change this thought with their four finned cuttlefish inspired Sepios robot.  Sepios carries a 20,000mAh battery, which is good for as much as 90 minutes of dive time with a top speed of 1.8 km per hour (~1.12 mph or 1.64 ft/s).  The current version is only rated for use at depths up to 10 meters (~32.8 ft), which is plenty to explore coastal waters and film wildlife.

Sepios can see effortlessly through a forest of seagrass, even in stormy conditions.  Each fin can be controlled separately allowing the robot to move in any direction with ease.  The team is now working on improving the coordination of its many sensors, for example pressure and humidity detectors and an on-board camera, laser and inertial measurement unit that help it avoid collisions.

Maybe Sepios will be swimming with Team UV’s underwater vehicle in the future!  🙂

Autonomous Navy Swarmboats

Posted by Andrew (Team UV) on January 27, 2015
Posted in: Well Read. Tagged: , , , , , , , , , , . Leave a comment

Swarmboats testing. Photo Credit: DefenseTech.org

The US Navy, specifically the Office of Naval Research, recently released information about their latest protection technology for their own fleet.  They have employed smaller autonomous boats, called Swarmboats, that swarm and intercept threats in order to protect the larger Navy ships.  Smaller, faster, and more nimble boats are fitted with a system called CARACas which stands for Control Architecture for Robotic Agent Command and Sensing.  To make this system as modular as possible, engineers have designed their control systems to be as “plug and play” as possible, allowing any boat to be retrofitted.  Initial testing showed that up to 13 Swarmboats can be linked up to protect a “mother” ship.  Right now the protection boats are used to detect and deter but have the capabilities to destroy upon command!

13 of our senior project vehicles all synced up under water?  Drool…

The motivation behind such a project was the terrible attack on USS Cole in 2000.  A small enemy boat filled with explosives simply approached the ship and killed 17 sailors and injured many others.  Swarmboats could have easily intercepted the enemy boat and prevented it from coming within deadly range.

More information can be accessed here.

Until next time…

The Reason Why Rolexes Are So Expensive

Posted by Ketton (Team UV) on January 25, 2015
Posted in: Open Mind. Tagged: , , , , , , , , , , . Leave a comment

Rolex watch. Photo Credit: http://www.mentalitch.com

Rolex is a universe of its own: respected, admired, valued, and known across the globe.  Rolex does just make watches and their timepieces have taken on a role beyond that of mere timekeeper.  Having said that, the reason a “Rolex is a Rolex” is because they are good watches and tell pretty good time.  There is a very real mystique behind the manufacture because they are relatively closed and their operations aren’t public.  The brand takes the concept of Swiss discreetness to a new level, and in a lot of ways that is good for them.  Here is a list of why Rolexes are so expensive.

1. They use an expensive and difficult to machine steel because it looks better.
Most steel watches are make from a common 316L stainless steel.  However, Rolex watches are made from 904L steel.  904L steel is more rust and corrosion resistant, and is somewhat harder than other steels.  904L steel, when worked properly, is able to take and hold polishes incredibly well.

2. Their movements are all hand-assembled and tested.
Rolex watches are given all the hands-on human attention you’d like to expect from a fine Swiss made watch.  Rolex uses machines for the process sure, but everything from Rolex movements to bracelets are assembled by hand.

3. An in-house foundry makes all their gold.
Rolex makes their own gold.  24k gold comes into Rolex and it is turned into 18k yellow, white, or Rolex’s Everose gold.  Large kilns under hot flames are used to melt and mix the metals which are then turned into cases and bracelets.  Because Rolex controls the production and machining of their gold, they are able to strictly ensure not only quality, but the best looking parts.

4. Rolex Dive watches are each individually tested in pressurized tanks with water.
All Rolex Oyster case watches are thoroughly tested for water resistance.  The way that this is often done at watch manufactures is with an air-pressure tank.  A watch is placed in a small chamber that is filled with air, and if the pressure changes at all, it means that air leaked into the case.  Each Rolex Oyster, as well as Oyster dive watches begins with this air pressure treatment.  In fact, each case is tested both before and after a movement and dial are placed inside of it.  Dive watches receive a separate treatment all together.  After being air pressure tested, Rolex proceeds to test the water resistance of each and every Rolex Submariner and Deep Sea watch in actual water.  This type of test is much less common.  Submariner watches are placed in large tubes that are filled with water to ensure that they are water resistant to 300 meters.  The test is extremely complex because Rolex employs a complex system for testing if water entered the case.  After the watches exit the tank, they are heated up and a drop of cold water is placed on the crystal to see if condensation forms.  An optical sensor then scans them for trace amounts of water.  Less than one in a thousand watches fail the test.

5. It takes about a year to make a Rolex watch.
Rolex produces almost a million watches a year, but surprisingly, no shortcuts are taken in the manufacturing process.  If you look at Rolex watches over time, they are more about evolution rather than revolution.  This idea of always improving versus changing goes right into their manufacturing process as well.  They are constantly learning how to improve quality through better processes and techniques.  The move from aluminum to ceramic bezel inserts is a perfect example.  Nevertheless, from starting to shape the parts of the case to testing a completed watch for accuracy, the process takes around one year.  Of course Rolex could speed this up for certain models if necessary, but each watch requires so many parts and virtually everything is made from base materials in-house.  Once all the parts for a Rolex watch are completed, they are then mostly hand-assembled and individually tested.  The testing and quality assurance process is rather intense.

These are only a few reasons why they are so expensive and this should give you some insight into how much TLC Rolex puts in their watches!  If you don’t believe me take a look at this video below of a Rolex being disassembled!

http://www.youtube.com/watch?v=wfNOgWGME_c

Enjoy!

Learning Arduino Part 5: Arduino Shields Galore!

Posted by Andrew (Team UV) on January 22, 2015
Posted in: Presentations. Tagged: , , , , , , , , , , .
Arduino Compatible Mega Motor Shield 1A-5-28V- Click to Enlarge

Stacked Shields on an Arduino. Photo Credit: robotshop.com

Arduino boards are very helpful and powerful tools to help connect the electronics world to the real world around us.  Like I said in Part 1 of my Learning Arduino Series, they can read inputs and control outputs very quickly; faster than any human can do manually.  With that said, an Arduino board, such as my handy UNO R3, can only do so much.  After an “Arduinonian” has experimented with all the things in their beginners pack, they often want to venture out to more complex and demanding projects.  Want to drive more than one motor?  Want to drive two DC motors and 2-3 Servos?  Want to connect your board to the internet or save data and images to an SD card?  There’s a shield for that!

Robot Shield. Photo Credit: OpenElectronics

Shields are commonly made for microprocessors like the Arduino UNO R3 to inject it with extra functionality.  They are designed to piggyback directly on top of your logic board, through the use of stacking headers, which can allow the use of pins not already in use by the shield itself.  Some shields allow programmers to pull more amperage for driving bigger, hungrier motors while others add GPS or Bluetooth capabilities.  There are WAY too many shields out there to describe in one post, so i will share with you some of the ones I have used and some that I plan to use in the near future.

1) Arduino Motor Shield R3

Arduino Motor Sheild. Photo Credit: Arduino.cc

The important thing about shields is that you want to make sure they are stackable with your specific board.  For example this motor shield is called R3 because it fits perfectly on top of the UNO R3 but wouldn’t fit on the earlier R2.  I bought this motor shield to do a few different projects that required me to use much stronger motors than the UNO R3 can handle.  With the shield installed, a programmer can pull up to 4A, 2A per channel, safely with operating voltages up to 12V.  It’s designed to drive relays, solenoids, DC motors, and stepper motors.  In fact, it can drive two DC motors independently or one stepper motor with speed and direction control for either case.  The shield can be powered by the same power supplied to the logic board (i.e UNO R3) or it can be powered by an external source through the VIN and GND terminals on the shield.

I found this shield to be very easy to use especially with everything already soldered on, even the headers.  Working with the supplied library was also a breeze and allowed me to get my projects up and running in no time.  I would totally recommend this shield for a beginner or even a professional looking to power up to 12V motors for its low price and easy implementation.

Click here for more info on this shield.

2) PowerBoost 500 Shield

Power Boost 500 Shield. Photo Credit: Adafruit.com

Power Boost 500 Shield. Photo Credit: Adafruit.com

 

This shield is the latest shield I have worked with.  I soldered up the headers and the on and off switch just yesterday!  This shield by Adafruit is potentially going to be used in our Senior Project design granted it performs well in testing.  The idea behind this shield is to take a single cell battery outputting 3.7V and boost the potential to 5V.  This allows a single cell battery to power up your 5V Arduino project on the go!  It also has a recharging circuit built in so that the LiPo battery can be charged via microUSB.  All the indicators for ON, Charging, Done, and LOW are there to let you know that state of the battery.  Another major plus is that depending on the size of the battery, it can fit nicely within the width and height of the stacking headers!  So far testing has turned out great with 5V being supplied to my project with the use of only a single cell 3.7V 2,000mAh battery.  This will save us plenty of space and take care of charging in one small stack-able package.  Like most shields out there this one needed to be soldered before use and for that reason, I would recommend this shield to anyone as long as they can solder or know someone who can.

Click here for more information about this Adafruit shield.

3) Shields I want to use in the near future

Long story short…any of these!

The link above lists some cool shields to get you all started but don’t be afraid to look around for new and unique shields.  Sparkfun, Adafruit, and other suppliers are constantly coming out with new stuff.  To be honest, the possibilities of what you can do with an Arduino are endless especially when shields can be stacked on each other!  Look out for my next Learning Arduino post about breakout boards and things I have needed to collect since starting this hobby!

As always thank you to everyone who has supported us and continue to share our posts and GoFundMe site.  We really appreciate it!

Until next time…

Fish Locomotion and the Future of Undersea Warfare

Posted by Brian (Team UV) on January 20, 2015
Posted in: Well Read. Tagged: , , , , , , , , , , . Leave a comment
Initial conceptual rendering for our UV done in April 2014.

Initial conceptual model for our UV done in April 2014.

First and foremost I apologize for the overall lateness of the content of this post, as I originally intended to publish this post in my previous round of posts, but due to time constraints decided to publish a post on a snake-proof full-body suit (equally interesting!) and invest a little more time into making this post a little easier to understand before publishing…hopefully it worked out, haha.  So as I noted a while back (while discussing the future of undersea warfare), with growing challenges in the undersea and technological domains, innovation is becoming more and more important within the realm of defense engineering (as well as all other fields of engineering).  One promising direction engineers are looking to in all fields of engineering is towards the application of advanced biomimetics (a.k.a. biomimicry) in their designs.  Why might engineers and scientists want to study how we can mimic fish, or other animals or nature in general?  Because nature truly is the ultimate engineer.  Animals have been optimized to perform the tasks that they need to and to do so efficiently and thus have been nearly perfected for their environments and their lifestyles.

Considering the facts just presented, it becomes a little more evident why undersea warfare (as well as other undersea activities and applications) may benefit from the implementation of biomimcry.  Take the Shortfin Mako Shark for example; this is the fastest species of shark in the world and it utilizes its large caudal fin (as will be defined later), slim, streamlined, torpedo-like body, and its stronger, faster-acting muscles (as enabled by its endothermic abilities, through which it generates additional heat through its unique metabolism, keeping the muscles warm and agile, thus defining the Mako as a “warm-bodied shark”) to reach cruise speeds of 25 mph and burst speeds up to 50 mph and leap 30 ft high!  Another example of the awe-inspiring abilities of marine creatures and how scientists and engineers have attempted to mimic them is that of the color- and texture-changing abilities of the octopus, as Andrew talked about a while back.

Shortfin Mako Shark. Photo Credit: Sam Cahir via dmarron.com

To better understand more specifically how engineers can utilize biomimicry in order to advance undersea vehicle technology, we will now discuss how exactly fish swim.  Fish generate forward motion, or swim, through what is termed locomotion.  Locomotion is simply a fancy word for describing movement from one location to another; animal locomotion may take many forms and can be seen in all types of environments, whether terrestial (on land), aerial (through the air), or aquatic (through the water).  There is a myriad of other qualifiers that can be used to further divide up the different kinds of locomotion (if you are interested, you can learn more about animal locomotion at this link), but we are going to solely focus on fish locomotion, that is, how fish get from one place to another.

Fish locomotion can be divided up into two main modes of motion: Body-Caudal Fin (BCF) and Median-Paired Fin (MPF).  The BCF mode accounts for about 85% of fish families’ main mode of propulsion, whereas MPF makes up for about 15%.  Now before diving into the swimming mechanisms associated with these two modes, we will make one more distinction: undulatory motion (also referred to as undulation) vs. oscillatory motion (also referred to as oscillation).  Undulation is by far the most common type of motion (both within the BCF & MPF modes) and can be thought of as a lateral wavelike movement; picture a fish seemingly weaving its way through the water or a rope with waves travelling down its length…this is in essence what undulation manifests itself as: undulation in fish movement appears as lateral waves travelling down the length of the fish’s body.  In short, undulation is lateral wave motion along the length of the body, relative to the body, as if the body was stationary but experiencing waves along its length.  In contrast, oscillation focuses more on the body being essentially rigid and moving the tail side to side…picture your dog wagging its tail, or a pendulum oscillating about the line connecting the pivot point to the base.  Now that we’ve got that covered, we can move on to quickly listing the common types of fish motion and listing a few examples!

Eel anguilliform lateral undulation. Media Credit: lyle.smu.edu

Time-lapse picture showing positions of a dog’s tail throughout its oscillation. Photo Credit: mediaorchard.com

Body-Caudal Fin (BCF)
This type of movement depends on the fish effectively wiggling its body in order to move its caudal fin sided to side, thus producing thrust which has components in the forward, backward, and transverse directions.  The largest component of this thrust is that in the rearward direction, thus the movement of the caudal fin propels the fish through the water.

Undulatory:
1. Anguilliform: With this kind of motion the undulatory waves are passed throughout the entire length of the body (except perhaps the head); because the entire body is extremely flexible, both forward and backward motion are possible.  The most typical application in which you would see this kind of motion would be in eel locomotion.
2. Subcarangiform: This motion is similar to anguilliform, but the forward 1/3-1/2 of the fish does not move, while the rest of the body still generates transverse undulations.  It is now significantly harder for the fish to swim backwards as it is not longer symmetric front to back and the forward portion of the fish is much more stiff than the rear.  Common examples of fish with this kind of motion would be most trout and salmon.
3. Carangiform: Also similar to anguilliform, but only the last 1/3 of the body acts to produce thrust and the caudal fin itself is usually more stiff to produce greater thrust with the reduced active length of the body.  Fish that swim like this are usually fairly narrow transversely, likely to increase the surface area used for thrust generation by increasing the height to width ratio; these fish also tend to be stiffer overall and faster moving.
4. Thunniform: In this group, all undulation is restricted to the caudal fin/tail and the region connecting the main body to the caudal fin (called the peduncle); these types of fish usually have very large, stiff caudal fins, have been optimized for high speeds and long distance travel, and are capable of generating hydrodynamic lift in order to compensate for the fact that many of them are not neutrally buoyant and thus need to move (and in doing so, generate lift) in order to keep from sinking.  Examples are most species of tuna and sharks.

Oscillatory:
1. Ostraciiform: These types utilize slow pendulum-like movement of large caudal fins and are similar to Thunniform, but operate much more slowly.  As a result, this type of swimming is usually either simply an auxiliary, low-energy style of swimming used by some MPF fish or, if used by fish as their main style of propulsion, those fish would generally have internal countermeasures such as poisons since they are incapable of fleeing predators.

Various physical characteristics of a generic shark, nearly all of which appear on most fish. Photo Credit: Wikipedia.org

Various physical characteristics of a generic shark, nearly all of which appear on most fish.
Photo Credit: Wikipedia.org

Median-Paired Fin (MPF)
This type of movement depends on synchronization of various combinations of usage of the pectoral, dorsal, pelvic, and/or anal fins.

Undulatory:
1. Rajiform: Characterized by vertical undulations along large pectoral fins…think sting rays and manta rays for example.
2. Diodontiform: Characterized by undulations that travel along large pectoral fins…like a porcupine fish!

Porcupine fish with undulating pectoral fins; Diodontiform motion. Media Credit: Tumblr.com

3. Amiiform: Utilize long undulatory waves along large dorsal fins, such as a Seahorse.
4. Gymnotiform: Uses undulations of a long anal fin; much like the Amiiform, but using the anal fin on the underside of the fish rather than the dorsal fin on the top side of the fish.  An example is the American Knifefish.
5. Balistiform: Anal and dorsal fins undulate; while rare, this can be seen in the Triggerfish.

Oscillatory:
1. Tetradontiform: Dorsal and anal fins oscillate either in phase (together) or opposite of each other; an example would be the Sunfish.
2. Labriform: Pectoral fins osciallate in a way in which they produce both lift and drag, which can be resolved into components, one of which would be rewards, thus producing thrust.  In essence, the fish flaps and rows its pectoral fins, producing thrust.  An example of a fish using this kind of motion would be the California Sheephead.

So there you have it, an organized view of the many sorts of propulsion mechanics associated with fish, each having its own advantages and disadvantages.  By studying these kinds of characteristics of fish, scientists and engineers can come up with innovative solutions by looking to the sea for the answers for the one constant truth for scientists and engineers alike is that we never stop learning and so when you can’t find a sufficient answer in your textbooks and theories, you need to be able to conduct experiments and analyze the world around you in order to come up with new ideas.

Team UV

Personal sketch of a conceptual UV following a submarine in the distance(April 2014).

This is exactly what engineers within the defense industry are doing currently as they conduct research and begin designs of new cutting-edge, innovative undersea vehicles that utilize biomimicry to provide for increased performance, better power efficiency, and increased stealth through the minimization of flow signature.  While we here at Team UV are not utilizing biomimicry in the design of our propulsor (for which we use something else all together), we absolutely have biomimetic influence within our design and as can be seen in the picture at the top of this article, have looked to adapt a streamlined shape and fin-like control surfaces in addition to a number of other biomimetic schemes (i.e. stability, maneuvering, buoyancy control, drag reduction, etc.) to produce a truly innovative solution that is currently in the manufacturing/assembly stage.  And so we again ask for your increased support through our fundraising campaign at GoFundMe.com/TeamUV as we near the end of our project in the coming months.  

As promised, in another week or two, we will release some pictures of the current vehicle design/model.

The Role of a Facility Maintenance Engineer

Posted by Andrew (Team UV) on January 18, 2015
Posted in: Open Mind. Tagged: , , , , , , , , , , .
Boston Water main break shoots 5 stories up

Not the university mentioned in the post, but you get the gif! Photo Credit: gifpins.com

Facility maintenance engineers are often under-appreciated in the world of science and technology but their important roles should not be overlooked.  They are tasked with various duties such as retrofitting machines and components, replacing equipment, and preparing maintenance schedules to make sure everything is working smoothly and continuously.  A strong background in machine design, electromechanical interfacing, HVAC design, and project management is required to keep a facility in working order.  Of all the other things not mentioned already a facility maintenance engineer has to assess damage and create a recovery plan in the case of a system failure.  Just last July, a local university campus experienced a terrible water main rupture.  The break of the 100 year old, 30 inch main resulted in the release of more than 20 million gallons of water compromising 900 vehicles, submerging athletic fields, and flooding nearby structures.  What a tough gig for any engineer!  The goal of this brief Open Mind is to show how I would reconstruct after such a terrible event.

Students making the best of the situation. Photo Credit: NBC News

The first plan after analyzing what exactly happened is to perform a major clean up.  I would establish a best way to clear the parking structures and other flooded areas to minimize damage done to structures, vehicles, and exposed equipment.  Pumps would have to be sized and storage/where the water will go will have to be determined.

Next, deep analysis of structural integrity will be performed to make sure all exposed buildings are sound.  Not only can water lead to mold and soften building material but it can also get into the thinnest cracks causing localized damage over the long run.  All exposed building would have to be cleared before being opened for use.

Pipe Robot. Photo Credit: technovelgy.com

Finally, active prevention action will be used to ensure no further catastrophes happen again and if they do, not to the magnitude of this recent event.  I would undergo a full and regular inspection of all major systems used by the campus/business.  Emergency detection systems can be developed to continuously monitor various system parameters and issue an alarm when critical levels are reached.  In an ideal world with endless money, I would also employ inspection robots that can go into piping networks or other systems that are hard to inspect and have them repair issues as they come up.  Easier said than done!

Look out for my next installment of Learning Arduino this week where I cover more example sketches and projects!  Also, continue to share and support our GoFundMe site!  We have raised over $1,600 thanks to our generous donors!

Until next time…

2nd Research Conference & Fundraising!

Posted by Brian (Team UV) on January 16, 2015
Posted in: Blog. Tagged: , , , , , , , , , , . 2 Comments

2015 National Conference on Undergraduate Research. Photo Credit: CUR.org

A few days ago, Team UV was selected to present some of our research regarding our underwater vehicle and its propulsion system at the 2015 National Conference on Undergraduate Research, which will take place at the Eastern Washington University from April 16th-18th!  Thank you to our readers for your support and for following our blog; we will not know what day, timeslot, or room we will be presenting on/during/in until early March.

Also, we want to thank those of you who have contributed to our fundraising campaign and mention that we have now raised $1,630 thanks to your generous donations!  Thank you for your support and please continue to help spread the word as we continue in the purchasing and manufacturing stages! 

We also want to note that no donation is too small and not a single penny donated will go to waste, it will all be used to increase the quality of our vehicle, to add capabilities (through additions to the sensor suite or additional drag-reducing technologies, etc.), and to enable us to conduct better testing (i.e. the construction of a flow tank for actual flow visualization).  As an example of this, we are excited to inform you that through some of your donations we have been able to get our hands on a superhydrophobic substance (from Hydrobead) that will help us to decrease drag on the exterior of our vehicle significantly through the repulsion of the surrounding water.  As follows from the above statements, any money that we raise above the $5,000 will be put directly into the project in one of many ways, including (but not limited to) those listed above.

Dyed water drops on wood coated with a super-hydrophobic substance. Photo Credit: TheFutureofThings.com

In addition to this, at this point, it is unclear as to where the funding to attend our research conference will come from (whether out of pocket or at least partially funded through our school’s research office), so all donations will help us significantly!  

Lastly, I want to remind our readers that we will be trying to post funding progress updates as often as possible and that you can find a full-sized PDF of our pull-tag poster on our Sponsors & Donations page if you would like to print one out and post it to help get the word out.  If you would like to help out in other ways, it would mean a lot to us if you would tell your friends/family/coworkers/etc. about our fundraising campaign (and possibly ask them to share it as well), share it on Facebook, or perhaps even just spread the word about TeamUV.org in general, as our biggest goal with regards to this website is to inspire interest in the fields of Science, Technology, Engineering, and Mathematics (STEM).

Any help is greatly appreciated and please come back Sunday for Andrew’s Open Mind post!

Compressible Flow Regimes

Posted by Brian (Team UV) on January 15, 2015
Posted in: Presentations. Tagged: , , , , , , , , , , . 1 Comment

Schlieren photograph of a scaled model of the SLS being subjected to (scaled) supersonic speeds. Photo Credit: NASA.gov

About a week ago, NASA tested the RS-25 rocket engine on the new Space Launch System (SLS), a launch vehicle that will drive the next generation of space shuttle deeper into space than we have been able to go thus far.  The video (shown below) has been made available to the public and provides an excellent excuse for the discussion of compressible flow regimes.

http://www.youtube.com/watch?v=hG8odscqlfI

In the past, our readers have been exposed to the world of fluid mechanics quite often (whether through aeroacoustics, turbulent vortices, hydrodynamic drag, or various other phenomena), and have even been exposed to the subject of compressible flow briefly, so today I am going to give you a bit of an introduction to the subject of gas dynamics and then I will explain the different flow regimes associated with compressible flow.

Fluid mechanics, as discussed previously on this website, is the study of fluids (liquids, gases, plasmas), their movement, and how they interact with internal and external stimuli (loading/forces, pressure differentials, dissipative effects, heat transfer, etc.).  Today, we will only be looking at gas dynamics, which differs from the study of liquids in that, for most purposes, liquids (i.e. water) are assumed to be incompressible.  With gases, this is not the case.  Due to the greater amount of space between free particles, gases have a much greater ability to be compressed.  Owing to this compressibility, the terms “gas dynamics” and “compressible flow” are often used synonymously to refer to the same field of study, as compressibility becomes a vital factor as the speed in a gas flow is increased.

Particle spacing in solids, liquids, and gases. Photo Credit: Wikimedia.org

 

As a result of this compressibility, two important phenomena are uniquely encountered within the field of gas dynamics that play a huge role in high speed gas dynamics, as will be defined shortly.  The first of these is the choked flow condition, which finds application in the usage of convergent-divergent nozzles (amongst other things), but which will not be discussed here for simplicity.  The second of these is the formation of shock waves.  Shock waves are essentially pressure waves that have coalesced together to form a “Mach wave”, which represents a discontinuity in the flow field….right, so what in the world does that mean?  If an object were to be stationary in the air and have pressure waves emanating from it, they would propagate out in all directions at the same speed (the speed of sound) and form concentric circles about the object.  However, as the object begins moving (within subsonic flow), the pressure waves become sent out at different times; in essence, the object sends out a pressure wave, then moves forward and sends out another, and so on (although, this happens basically continually).  

Shock wave formation. Photo Credit: JetEngines.Wordpress.com

As the object’s speeds increase, the center points of these waves get further apart, and thus the waves become compressed in the direction of motion, and expanded in the opposite direction.  Eventually, if the object continues moving faster, the object will be moving at the speed of sound, meaning that the object will be travelling at the same speed as the pressure waves are being sent out…in essence, the object has matched or caught up with the pressure waves that it is sending out, and so when the object sends out more pressure waves, they can no longer propagate forward from the object, but rather travel at the same speed, while the portions of the waves traveling backwards are now being left in the dust…figuratively speaking.  The waves that are being emenated from the object all at the speed of sound are now really close together and essentially stack up and coalesce into one solid pressure wave that is termed the shock wave.  This shock wave can be heard as a “sonic boom” due to the discontinuity or abrupt change in pressure across the shock wave (forward of the wave, the flow is moving at the speed of sound and very low pressure, behind the wave, the flow is moving slower and at a higher pressure).  As the object speeds up even further, the object is now starting to outpace the pressure waves all together in what is called supersonic flow, so that the object is leading the waves, which begin to form a mach cone around the object; inside of this mach cone is referred to as the zone of action, while outside of the cone is referred to as the zone of silence.  If the object moves even faster, it will eventually get to a speed so high (that of hypersonic flow), that the shock cone will tightly hug the skin of the object so that the distance is so small between the object and the shock wave, that the air gap (the shock layer) begins to heat up due to viscous effects and the aerodynamic heating effect, leading to what we term “high-temperature chemically reacting flow”; the flow is so hot that the gas begins to dissociate or ionize!

So at what speeds does this all occur?  To find this out, we define the Mach Number (a.k.a. M or Ma) as the ratio of the object’s speed to the local speed of sound; to understand this, a value of 0.5 would mean that the object is moving at half of the local speed of sound, 1.0 would mean the object is moving at the local speed of sound, and 2.0 would mean the object is moving twice as fast as the local speed of sound.

Compressible flow regimes. Photo Credit: Wikimedia.org

Up to a value of Ma 0.3, the flow is described as incompressible and thus is analyzed similarly to other incompressible fluid dynamics such as most liquid flow.  An example of incompressible flow would be what the baseball encounters when you play catch with a friend.

Baseball in incompressible flow. Photo Credit: Hilltop.Bradley.edu

Once the object hits Ma 0.3, the flow is considered compressible and subsonic in that the object is still moving slower than its pressure waves.  An example of subsonic flow would be the flow around many .38 Special bullets.

Bullet fired from a Smith & Wesson 686 .38 Special. Photo Credit: Wikimedia.org

Once the object reaches about Ma 0.8, transitional instabilities begin to set in and persist to about Ma 1.2; this regime is termed the transonic flow regime and can be seen in basically any application wherein an object is accelerating to supersonic speeds, as the object must pass through the transonic regime to reach the supersonic regime.

Transonic flow patterns. Photo Credit: Wikimedia.org

Above Ma 1.2, the shock waves have generally been established in full and the vehicle can be said to be in the supersonic flow regime.  Applications include supersonic jet engines, such as those found in many military aircraft and supersonic ammunition.  More photos will be included here since supersonic flow is the meat of this post.

Shock diamonds in a supersonic XCOR Liquid Oxygen-Methane engine. Photo Credit: WordPress.MrReid.org

F-15 showing shock diamonds while in supersonic flight. Photo Credit: RobHansonPhotography.com

Supersonic bullet showing shock cone, pressure waves (look closely), and turbulent wake; visualized using the shadowgraph method. Photo Credit: Wikipedia.org

Lastly, above Ma 5, the aerodynamic heating effect comes into play and the flow enters the hypersonic regime.  Applications are hard to come by as this is a subject of a great deal of current research within the fields of mechanical and aerospace engineering (more specifically fluid dynamics); however, one instance of this kind of flow that nearly everyone is familiar with is that of the space shuttle, especially during what is termed re-entry.  In fact any re-entry vehicle will experience hypersonic flow, and very likely “hyper-velocity flow” which is essentially an upper range of hypersonic flow speeds.

Hypersonic wind tunnel testing at Ma 6. Note the thin nature of the shock layer. Photo Credit: Gizmodo.com.au

Time lapse of LGM-118A Peacekeeper missile re-entry strike bodies touching down, after having traveled through the atmosphere at speeds up to approximately Ma 20. Photo Credit: Wikipedia.org

 

Origami Engineers

Posted by Ben (Team UV) on January 13, 2015
Posted in: Well Read. Tagged: , , , , , , , , , , .
Crane

Origami crane. Photo Credit: Wikipedia.org

Most of us can remember the days in elementary school where we learned to make paper cranes, flowers, boxes and all manner of things just by folding paper.  I was never one to master the art of origami but I can make a pretty nice paper air plane!  This technique of folding paper has generated a lot of interest in the engineering world.  The National Science Foundation has provided a grant to a few top universities to research this.  The goal is the creation of materials that can fold up into very small places and then unfold when needed.  Imagine a solar collector that could unfold like a flower in sunshine then collapse again at night or when power is not needed.  Read a full article about it on the American Society of Mechanical Engineers’ website here: https://www.asme.org/engineering-topics/articles/design/engineering-meets-art

Engineering Jumper Robots with Compressible Fluids

Posted by Brian (Team UV) on January 11, 2015
Posted in: Open Mind. Tagged: , , , , , , , , , , . Leave a comment

Newton’s 3rd Law of Motion. Photo Credit: Buzzle.com

Prompt: Boston Dynamics is a company that specializes in producing robots that can really do the unimaginable.  Take Sand Flea.  Sand Flea weighs 11 lbs and can jump to heights of up to 30 ft.  Such a feat represents a very attractive design goal across all industries for the coming years: the ability to store massive amounts of energy and release it very quickly.  Considering that these high energy-density type systems are in fact the way of the future, using what you know about energy come up with either at least 3 ways of storing/quickly releasing a large amount of usable mechanical energy or come up with one way and describe at least 3 ways to look at your solution.

There are countless applications for these kind of high energy-density storage, quick release type systems; however, in this post, we will simply be looking at a few design considerations that a mechanical engineer would have to account for if he/she wanted to design a robot capable of jumping to great heights by taking advantage of the expansion associated with the release of compressed gases.

As shown above, Sir Isaac Newton’s 3rd Law of Motion essentially states that for every action, there is an equal and opposite reaction.  This simple statement has profound complex consequences in the real world.  If you have ever seen a spaceship lift off, felt the recoil from a firearm, had a hammer bounce back at you after hitting a nail, or wanted to see what would happen if you were to use a fire extinguisher as a booster while sitting in a rolling chair, you have seen the phenomena that Newton’s 3rd Law of Motion is referring to. 

Fire extinguisher + rolling chair = fun. Media Credit: Brooklynn99Insider.com

Now in reality, things get much more complicated as there are many inter-dependencies that affect these reactions (i.e. the reaction of air resistance on the skin of the spaceship, the rerouting of gases in automatic weapons to chamber the next round and reduce recoil, the elastic properties of the steel head of the hammer, the rolling friction of the chair wheels or that associated with the bearings of the wheels, and the list goes on…).

So getting back on topic, what would we need to consider if we wanted to design a robot that used compressed fluids to jump?

Fluid Mechanics
As a class of fluids, gases are much more compressible than liquids; this fact, in combination with the tendency of gases to fill the shape of their containers (or flow paths) makes them ideal for use in high-compression fluid storage to be used for imparting large amounts of kinetic energy to objects via momentum transfer from their expansion kinetics.  By storing a large volume of gas under heightened pressure within a properly suited pressure vessel (PV), large volumetric expansion ratios/rates can be realized when the gas is released.  This gas expansion leads to massive amounts of energy being released very quickly from these areas in which massive amounts of fluid can be stored in a very compact space (thus high energy density storage and fast release).  The energy and momentum associated with this gas can be used to propel our robot up and into the air, but know what?  Did we intend to design our robot to be single use or do we want it to be able to jump again?  We need to find a way to refill the system.

The means by which these systems are refilled or “recharged” is most often dependent on the kind of gas being used.  In order to replenish your energy stores in an air-based system, you could simply pull the air from the atmosphere using an air compressor (although this becomes significantly harder when you are for example 500m under the ocean’s surface).  Another complication associated with this method is the fact that an air compressor may not be ideal for our application on the basis of size, weight, vibration, noise, power requirements (as the air compressor will up the robot’s power requirements and thus decrease its run time for the same amount of power supply or even necessitate the use of all new control circuitry), etc.

This situation is complicated even further when the gas being used is not air, as now you have to store all of your gas reserves unless you can find out some way of extracting the gas you need from the atmosphere, which is simply not feasible, especially on such a small scale.  So how do we get around these limitations?

Daisy Red Ryder BB Gun. Photo Credit: ehstoday.com

Many air-based systems use air-pistons in order to recharge their compressed gas reserves as anyone who has ever had to pump a BB gun or water gun has experienced.  The mechanism for actuating this piston is not always something as obvious as the lever action on your Daisy Red Ryder BB gun (remember to always practice proper gun safety, lest you shoot your eye out…referencing the movie A Christmas Story).  Some systems may have a protruding pin that (when depressed) cycles a small pump compressor or reciprocating piston to recharge thy system.  In some applications, exhaust gases may be re-routed and used to actuate the compressing mechanism.  Technological creativity knows no bounds and, as such, it is more realistically finding a way to recharge a system comes down to design time, costs, and other system-level tradeoffs.  Would it not be easier if we simply did not allow the gas to ever leave the system in the first place?

We could create a closed-system by using a highly elastic material to cover the exit nozzles of our robot, so that when we released the gas, it would rapidly balloon out and propel our robot through the elastic collision interaction mechanics between the gas-filled elastic material and the ground (think Newton’s 3rd Law of Motion) without expelling the gases to the atmosphere.  To better understand this, visualize taking one of those squeeze toys where the eyes bulge out (see below) placing the toy with the eyes against the ground and then filling the eyes with a ton of gas really rapidly and watching the thing fly up in the air!  This is just one example of the open-minded nature of engineering problem solving.  The only bummer would be that in reality, this feat would likely be far more difficult than stated here and would likely require the development of a custom material with the proper amount of elasticity or “stretch”, tensile strength, strain-recovery time (how fast the material returns to its original size/shape), and would likely need include stiffer/more rigid pads where contact would be made with the floor so that the material could transfer more of the gases kinetic energy to the ground (rather than simply absorbing all of the gas’s energy through the material’s ductility).

Eye-bulging squeeze toy. Photo Credit: Alibaba.com

Thermodynamics/Heat Transfer
In order to bring this article to end sooner rather than later (sometimes I get carried away and don’t realize how much I’m writing, so my apologies!), I will quickly move through this subject for consideration as well as the 3rd one. 

Most gases would experience significant thermal energy generation under large compression ratios and thus the surrounding system would likely require cooling to prevent damage to the electronics or to the user; this cooling could be accomplished by passive controls such as extended surfaces/fins or forced heat transfer by way of a fan – the cheapest active thermal control.  You have likely seen both of these types of systems mounted to your computer’s CPU.

Fan mounted to extended surfaces on a CPU. Photo Credit: Wikipedia.org

Mechanics of Materials
A very noteworthy consideration in this application would be the strength of the pressure vessel (PV).  Depending on gas used, compression ratio, allowed temperature rise and transmittance of impulse (high energy transfer over small time period) to the PV, hoop stresses (circumferential) can become significant and therefore require thicker PV sidewalls, use of stronger material for the PV, or rib reinforcement of the PV.

Pressure within a pressure vessel (in this case a CO2 canister). Photo Credit: science-of-speed.com

So anyways, there is a long-winded look into just a few of the many, many things a mechanical engineer might consider in their design of a robot capable of jumping to great heights using compressed gas.  One of the many beauties of mechanical engineering is the fact that it is such an incredibly open-minded field that requires creativity, intelligence, determination, and the realization that there is never one right answer.

So What’s the Deal with 3D Printing?

Posted by Ben (Team UV) on January 8, 2015
Posted in: Presentations. Tagged: , , , , , , , , , , .

 


The idea of 3D printing is spreading around into all kinds of different disciplines, from cooking to make up.  In engineering the idea of 3D printing has been around for a while now.  But more recently it has become accessible to the average consumer.  Some organizations made 3D printer designs open source, meaning that they published their designs on the internet free of charge.  This allowed anyone with some know how to make their own.  Once the average hobbyist could invest in the technology it began to get more interest and eventually has become the thing that it is today.  As an additive manufacturing method for prototypes, or single production runs, where strength isn’t a huge concern 3D printers open up a huge world of design to the interested population.

Team UV Phase I Photos & Fundraising Update!

Posted by Brian (Team UV) on January 7, 2015
Posted in: Blog. Tagged: , , , , , , , , , , . Leave a comment

 

Team UV Badge, representing our principal application (ISR), and our potential future applications (Mine Detection, Underwater Inspection, and Exploration).

Team UV Badge, representing our principal application (ISR), and our potential future applications (Mine Detection, Underwater Inspection, and Exploration).

Team UV would like to update our readers and supporters with regards to the progress you all have helped us to make through our fundraising campaign.  As of today (January 7th, 1525 hours), we have raised $1,620 of our goal thanks to your donations!

As a way of saying thank you and hoping to share a little more about our project with you, we will be publishing some images of our project over the next few weeks.  The reason we have refrained from posting any pictures from our project in the past was due to the proprietary nature of many of the systems on our vehicle (and the vehicle as a whole), but we are realizing more and more how important it is that we share a little more of what we are doing with our supporters.  So without further ado, below we have posted 2 pictures of SHEILA-D (Submerged Hydrodynamically-propelled Explorer, Implementation: Los Angeles – Demonstrator). 

Left: SHEILA-D producing thrust. Right: SolidWorks 3D model of SHEILA-D.

Left: SHEILA-D producing thrust. Right: SolidWorks 3D model of SHEILA-D.

SHEILA-D was our propulsion system demonstrator that we designed, built, and tested over a span of 36 days and 850 (by conservative estimates) man hours during Phase I of our project (which took place during our Machine Design lecture/lab combo in Spring 2014).  The goal for SHEILA, was to demonstrate the ability to provide thrust with our innovative underwater propulsion system, and in this respect we succeeded.  However, we were aware of many shortcomings from this initial design (i.e. poor material choice as influenced by cost/time limitations, poor tolerances, etc.) and thus revamped our efforts with regards to the propulsion system during Phase II [the senior project portion/development of the entire vehicle from late Spring 2014-mid Spring 2015 (project symposium)].  For more information on the history and plans for this project, please check out our About page.

We are currently in the purchasing portion of Phase II (to be followed by manufacturing/assembly, programming, testing, final analyses, and report/presentation preparation) and thus could use funding now more than ever.  We would like to thank all of you for supporting our efforts and ask that you please continue to share our website and our fundraising campaign (GoFundMe.com/TeamUV) with as many people as possible.  No donation is too small and for those who know the team personally, offline donations are welcomed as well.

This post will be reposted on our fundraising page, and 1 week from now we will post some pictures of the original Phase II full-vehicle concept, with the actual Phase II vehicle computer model pictures coming 1-2 weeks after that, so please be sure to check back often and remember, tomorrow Ben will be posting a Presentation post at 1000 hours!

One Small Step to Breathing Underwater!

Posted by Abraham (Team UV) on January 6, 2015
Posted in: Well Read. Tagged: , , , , , , , , , , . Leave a comment

 

Oxygen-absorbent crystals before (left) and after (right) becoming saturated with oxygen. Photo Credit: TheHigherLearning.com

71% of the Earth’s surface is covered with water and, for the most part, it is unexplored by humans…until now!  Scientists from the University of Southern Denmark in conjunction with the University of Sydney, Austrailia have discovered a crystalline material that is capable of absorbing oxygen from both air and water!  This revolutionary material can bind and store oxygen in high concentrations then control the release time of that oxygen depending on what the user needs.  The benefits to this are unquantifiable but could be especially beneficial to deep sea divers and to those suffering from respiratory ailments.

A study led by professor Christine McKenzie alongside Jonas Sundberg of the University of Southern Denmark  involved about 10 liters of microscopic grains of the material and found them to be enough to suck the oxygen out of a room.  Even just a few grains contain enough oxygen for a single breath and that material can even absorb and supply oxygen from water surrounding deep sea divers.  The oxygen saturated material is so effective that it is comparable to 3 full pure oxygen tanks under pressure!  One of the key ingredients is the metal cobalt in the material which controls the process of absorption which gives it the molecular and electrical structure to be capable of absorbing oxygen from air and water.  Remarkably the absorption and releasing process can be done many times without losing the ability much like a sponge in water.  The impact that this discovery will have on the medical field as well as exploration will be monumental and I look forward to it.  For more information please visit: http://www.collective-evolution.com/2014/10/10/absorbing-crystal-can-steal-oxygen-from-air/

 

Fireside Fluids

Posted by Ben (Team UV) on January 4, 2015
Posted in: Open Mind. Tagged: , , , , , , , , , , .
Fire

Hot beverage and a book by a fireplace. Photo Credit: honeymoon-adventures.com

Winter is a wonderful time to sit by a fireplace, drink a hot beverage, and listen to the rain pound the windows from outside.  Even in this cozy setting the engineering principles of fluid mechanics are hard at work.

Flames rising from burning logs always have a way of mesmerizing me, the way they dance mischievously around and leap for the chimney captivated my curiosity since I was a child.  Now that I am an engineering student I can explain what causes them to act the way that they do.  There are two basic principles that can explain this.  The first is as simple as the fact that hot air rises, the hotter the air the faster it rises.  The second is that as things get hotter they emit radiation that we see as light, like red hot metal.  If you put these together you find that flames are actually a mix of air and smoke that are so hot that the radiation they emit is in the visible spectrum.  The flames dance over large fires because of disturbances in the air and because the air is so hot that it rises fast enough for the air to become turbulent.  Yet over a candle the flame can stay relatively steady.  This is because the air is rising slowly enough, and with few enough disturbances to remain laminar, or steady.

For me the pounding of the raindrops on the windows bring another level of authenticity to the fireside.  That being said I am from San Diego so I don’t get rain often in any season.  All of this water stays up in the clouds floating across the land and then finally dumps to the ground below.  But what causes the trapped water to finally fall?  In damp air there is a lot of water vapor that would like to form together and form droplets but it takes a lot of energy.  The energy required to form a droplet is related to the surface area of the droplet so a perfect sphere of water forming is very unlikely, there is simply too much energy required to maintain the surface area of a sphere.  However, if there is a speck of dust floating around in the air water can form to it.  The water only has to maintain a fraction of a sphere of surface area because the dust covers the rest.  As water vapor condensates on these small particles they become heavier and eventually fall out of the bottom of the cloud and bring the water back to the ground.

Finally no cozy fireside day is complete without a hot beverage by your side.  These beverages never stay hot for long enough.  This is because of the natural convection moving air around your mug.  While that may sound a tad complicated, it’s based on the same principle that the flames were above.  Hot air rises.  This means that the air around your mug was heated by the hot beverage, this hot air rises away from the mug and draws cool air up to take more heat.  The cycle continues until you finish the drink or it gets disappointingly cold.

Next time you sit by the fire with your drink think of what you’re seeing and let your curiosity take you into the realm of engineering.

Curved Tops and Flat Bottoms: The Tale of Airfoils

Posted by Abraham (Team UV) on January 1, 2015
Posted in: Presentations. Tagged: , , , , , , , , , , . 2 Comments

 

Flow past an airfoil. Photo Credit: av8n.com

Happy New Year from Team UV!  Hope you all enjoyed the past year and are looking forward to some new and beautiful things to come in 2015!  Being the first post of the year, I’ve decided to start it off right with something uplifting!

Airfoils.  Who needs them, right?  Well actually a lot of people do, especially if you want to fly.  Looking at an airfoil, you might believe that lift is created because one side is curved and the other flat.  This however would suggest that lift is only possible in that particular orientation but that is simply not true!  If it were, then how could airshow pilots routinely fly upside down for extended periods of time?  These are the questions we should be asking people!

Airfoil pressure field distribution. Photo Credit: av8n.com

To fly, it is not necessary to change the shape of the wing when inverted.  Actually, any normal shaped wing can fly fine when inverted.  It may look a bit weird and the inverted-stall may not be optimized but it does create lift by the same principles as the right-side up wing.  Remember, lift is more a function of angle of attack than simply shape.

Airfoil chord and camber lines. Photo Credit: av8n.com

The chord line is a straight line drawn from the leading edge to the trailing edge of the airfoil.  The mean camber line is a curved line drawn from the leading edge to the trailing edge that always stays halfway between the top and bottom of the airfoil.  The amount of camber an airfoil has is determined by the greatest distance between the mean cambered line and the chord line.  If the mean chamber line and the chord line are the same, then you have a symmetric airfoil.  A general rule of thumb is that symmetric airfoils are preferred to highly cambered airfoils in small angles of attack, and the opposite is true for higher angles of attack.  This is shown in the figure below where the airfoil designated 631-012 is symmetric and 631-412 is the slightly cambered version.  Besides one being slightly cambered, the airfoils are pretty much identical.  Beyond 12 degrees relative angle of attack you can see that the cambered airfoil has a big advantage over its symmetric counterpart.  The cambered airfoil does not stall until a higher angle of attack around 18 degrees and as a consequence its maximum coefficient of lift is much greater.  An intuitive explanation would be simply that the slight camber allows for the leading edge to slice through the air easier.  Taking this to another extreme, a reverse cambered airfoil would not be a good idea because it would stall even earlier than then symmetric airfoil (which is why you don’t see these).  A reason for having a large camber would be in landing or lifting off situations and usually extending the flaps of the wings is sufficient in increasing the camber.

Airfoil Coefficients of Lift & Drag as a function of Angle of Attack. Photo Credit: av8n.com

Effect of wing flaps on camber. Photo Credit: boldmethod.com (modified)

Effect of wing flaps on camber.
Photo Credit: boldmethod.com (modified)

Again it is important to reiterate that lift is more a function of the angle of attack rather than simply the shape of the airfoil.  If the coefficient of lift was only dependent on the camber of the wing (which doesn’t change often during flight) then the plane would only be flyable at a special airspeed designed for that particular cambered wing.  In reality however pilots have to constantly change the angle of attack to maintain steady lift.  For more on lift, airfoils, and flight please visit: http://www.av8n.com/how/htm/airfoils.html.  Have a happy new year!