For much of our design we had to do some complicated analysis on the way the water acts around our vehicle. To do this we had to do some Computational Fluid Dynamics. The complex math involved in these calculations has been briefly touched on in past posts, but this post is here to tell you how we did it. Autodesk offers a massive suite of analysis software for free to students and one of them does the analysis we need: Autodesk Simulation CFD. There are many great tutorials out there on how to do this but here are the basics we used.
- Create an external volume: our device interacts with the water around it so we needed to model that.
- Then we assigned materials to each component. Each part has a different density and surface finish that will affect its interactions with the water so we needed to assign these values.
- Then we set the boundary conditions. These are values of pressure or velocity that remain constant or change at a prescribed rate. For ours we set our pressure far away from the device to zero gauge pressure.
- Next we assigned a rotational velocity to our propulsor. This sucker moves the water so we gotta have it spinning.
- Then we mesh the whole thing. The automesh feature in the program does a pretty good job. The mesh connects all of the data points; the calculations will be done at each of these points so the more of them there are the longer the analysis will take.
- Then click solve and take a nap, these things can take a while to solve!
All of this analysis is right at your fingertips if you know where to look (and happen to be a student!) It’s pretty cool the things you can find out!