[AntonioG]

Hello to everybody, I'm new in this forum. I'm working in my master thesis trying to estimate the hydrodinamic coefficients of an AUV (Autonomous Underwater Vehicle). I have already calculated some of them at constant speed but I'm having problem when I try to accelerate the flow.

What I want to do is to impose a transient velocity conditión with constant acceleration so I can compare the results with the constant speed ones and obtain the so called added mass (virtual mass).

I've tried to set the intel velocity as a function of time, with velocity field function as Vx=constant*t.

The simulation converge but the problem is that the results make no sense, the velocity distribution and the viscous forces make sense but the pressure distribution doesn't and the pressure forces are too high.

I attach a picture of the pressure distribution so you can see can I mean.Presión, velocidad variable.jpg

Can somebody help me with this? I'm really stuck, and I tried a lot of combinations of inlet and outlets

Or Does somebody know another method to estimate the added mass?

Thank you very much in advance