On 1/5/13, Bill Gosper <billgosper@gmail.com> wrote:
Oops, sorry. http://gosper.org/What%20Don%27t%20You%20Understand.JPG --rwg
Thanks Bill! These sites selling the shirt: http://www.scientificsonline.com/what-part-of-t-shirt-10471.html http://lawrencehallofscience.stores.yahoo.net/whatparoftsh.html each identify it as "Navier-Stokes star gas equation". This site: http://www.catstees.com/s4order.htm says "... this is the formula for rocket fuel." It's also being sold at CalTech (start at www.bookstore.caltech.edu and use their search box to search for "What part of") My humble search skills aren't finding any sure proof, but I found a discussion: http://boards.straightdope.com/sdmb/showthread.php?t=371315 which gave a bunch of leads, including one comment that says, "I emailed the t-shirt site to the local college astronomy professor and he confirmed that it's the Navier-Stokes star gas equation," and also this: -- quote -- Its an integral for a fluid control volume problem. Basically, it is if you stood in a river and watched a glob of fluid go by and you wanted to know the net force on that glob. To do that problem you define an imaginary boundry that encloses the fluid The first integral term is the compression of the fluid in question. I forget exactly what beta is defined as, but it relates to the Volume/Surface Area. Doing that integral returns the net force on a control volume due to expansion/compression of the fluid. The second integral is calculating the net force on a moving, rotating reference frame in a fixed reference frame. Its basically a bunch of math stuff, which the derivation of I don't want to go into. As a tid bit, the 2*w*V_xyz term is what is commonly known as the coriolis effect. The third integral is a surface integral that comes from the bernoulli equation applied accross the control surface. I am not sure, but it appears that this part of the equation is wrong. Instead of V_xyz, I believe it should be V_xyz^2/2. The last term is an integral that accounts for the change in momentum (remember that change in momentum/change in time equals force) of the fluid inside the control volume. This is basically the most scary and unweildy equation you could think of for a Mechanical Engineer. [...] -- end quote -- Also, in my searches I found a couple of equations in the "Integral Momentum Theorem" and "Comments on Rocket Equation Derivation and Examples" documents on this syllabus: http://my.fit.edu/~dkirk/4262/Lectures/ that look suspiciously similar. -- Robert Munafo -- mrob.com Follow me at: gplus.to/mrob - fb.com/mrob27 - twitter.com/mrob_27 - mrob27.wordpress.com - youtube.com/user/mrob143 - rilybot.blogspot.com