| MadSci Network: Physics |
Hi Mike,
That's a toughie! Unfortunately, the motion of any object through a fluid involves a complex array of interactions.
If all that you want is a drag force, you can make a crude (very crude) approximation, which ignores many effects of streamlining and turbulence. Imagine an object with cross section A moving through a fluid of density d. The amount of mass per unit time of fluid which the object encounters is given by A*d*v, where v is the relative speed of the object and the fluid. If it accelerates all of the fluid up to v, then the drag force looks like A*d*v2. In actuality, there's a multiplier, f, in front, that ranges from 0 to 1. Most hydrodynamics or aeronautical engineering books can give you more detailed formulas.
If your "blockies" are going to be swimming like fish, then what you might want to do in practice is to apply some sort of realistic-looking, but not necessarily physically accurate motion to them. You could even specifiy a type of motion for a given type of movement. You could base this upon actual fish motions, which are being simulated. One place where you might find some information is the RoboTuna site (http://web.mit.edu/afs/athena/ org/t/towtank/www/tuna/robotuna.html) or the Robot Pike site (http://web.mit.edu/towtank/www/pike/< /A>. Others are at http:// www.biology.ualberta.ca/jackson.hp/IWR/Content/Anatomy/Swimming/Information/ index.php, and http://www.css.tayloru.edu/instrmat/ graphics/hypgraph/animation/art_life/fish.htm
Try the links in the MadSci Library for more information on Physics.