Water Rocket Simulation



I am using a math program to simulate the rocket flight.  I am see
that I am getting a slightly longer "burn" time with my sim than the
sim from:

http://polyplex.org/rockets/simulation/

Do you guys think the force of inertia would add a significant (non
negligible) amount of pressure to the water at the nozzle?  If he has
included this factor in his calculations of burn time, then I would
imagine his burn time would be shorter.

The website gives:

BO @ t=.595s

My calculations:

BO @ t=.688s

This is for a 9mm nozzle with 50/50 air/water in a 2L bottle.

I like using a math program, because once I get the sim all dialed in,
I can run optimizations on it.

Thanks,
Chris Maness