I'm looking for a basic (and hopefully, free) piece of software for a project I'm working on. I'm building a little submersible robot with a group of students, and I'd like to find some modeling software that would allow us to do some basic simulations of our design. Ideally, this would be a visual-oriented app... something that would allow us to make a little 3D model , and then do the most basic of fluid calculations (like the change in flow depending on the angle of our propeller, etc.). Can anyone out there direct me to something like this? I've asked for a copy of NASA's TetrUSS program, but I seem to recall requesting it a few years back and never hearing back from them. I also have requested a free student license for FlexPDE. One of those might do the trick, but I'm open to suggestion. I'm a Ph.D. student, so I can figure out an intermediate level program, but I'm working with 6th grade students, so I'd like the output to be something they can grasp. Any assistance would be most appreciated! Maybe some of you enterprising developers out there have been working on a pet project and could use a small group of needy beta testers? This is for a NSF GK-12 project in a inner city elementary school.