The "Mathematics in Motion" T-shirt shows nine frames of an animation of two vortices merging. The colors show vorticity, or how fast the fluid is turning. Red is high positive vorticity and blue is zero vorticity.

front/pocket

If two vortices of the same sign are near each other, they will rotate around each other. Close vortices, like those shown, will merge into one.

This animation was produced by a computer program which represents the laws of fluid motion using differential equations. The model is used to study how real fluids, like water in the ocean, behave. In the ocean energy cascades from large scale vortices to eddies and finally to small scale turbulence. Vortices of different size and sign interact by merging, aligning, or translating. Using the computational fluid model, we can specify initial conditions and conduct experiments that would be impossible to do in the real ocean.

back of T shirt: