Imagine if you will, you are a worker in a water pumping plant. The steady whrr of the massive pumps have become a constant melody in your day. Around lunch time you sit down next to an open low pressure access panel because you enjoy watching the water flow down the large steel river. It looks so peaceful before it gets to the pump, where chaos and turbulence reign. Lost in your thoughts some of your Chinese take out falls into the water. All of a sudden the roar of the pumps dies down a bit. They are not working nearly as hard as you are used to. You have just discovered Tom’s effect.
Tom’s effect occurs when a small amount of high molecular weight polymer is added to a fluid before it reaches a pump. The polymer aligns to the flow and keeps the flow laminar for a longer period of time thus reducing the amount of work required to pump the fluid. Ok, let’s break that down. A polymer is a string of atom combinations called monomers. High molecular weight means that there are a lot of atoms in the monomer and that there are a lot of monomers that make up the polymer. Think of a chain, monomers make up the individual links of the chain while the whole chain makes up the polymer. When you make the links longer and add more of them you get a really long chain. When you add a bunch of these chains to water they line up with the flow and stretch out. This makes it harder for the water to mix and keeps it flowing in a regular line for a longer time. It’s much easier to move a fluid that is flowing smoothly, like a calm river, then it is to move water that is turbulent, like rapids. That little bit of Chinese food contained a lot of Guar gum, a common thickening agent in foods that is also a high molecular weight polymer.
Tom’s effect can be seen in nature several places. One prime example is fish slime. Fish are covered in a film of mucus that is also a high molecular weight polymer. This allows them to slip through the water with ease. In a marine ecosystem where energy is the currency a slimy fish is a wealthy fish.