CFD and FEA

In general the best boundary conditions are those that mathematically model the physical situtation you want to analyze (which in this case we do not know what it is).

well I have a swimming robot , and I want to make CFD analysis around it

Actually, I am an electrical engineer, so fluid dynamics is far a way from my academic field. I will be thankful if you helped me with this.

regards,

farah

Again, it depends on what you want to model. BTW, I am a nuclear engineer and CFD is out of my scope.

I think I can help you. Boundary conditions are those values which are various forces, moments, etc., For the robot swimming, the possible boundary conditions can be the water velocity (upstream or downstream or in still water (v=0 m/s)), temperature, pressure of water, angular velocity of robot hand (for swimming), gravity acceleration (9.81 m/s2), weight of the robot. As far as I concerned these are boundary conditions and these conditions have some other forms like the parameters (velocity,pressure etc.,) can vary with time (in sine or defined wave form) or may be user defined functions (in the form of code with equation describing the movement or parameters).

I think you want do analysis in the CFD for understanding the robot components' resistance. In this case we don't do just CFD analysis on solid components. Of course that the fluid flow in some cases such as aircraft is so important but, this type of loads bring the cracks and/or other phenomena. The parameters that Ananth told are important. But maybe you are searching in FSI simulations that are mentioned in my message. that for structural simulation you should consider other boundary conditions.

Dear friends,

I am studying turbulence with the aid of CFD by solidworks, actually I have a confusion about the inlet , outlet,ideal wall and real wall conditions. I dont know what is best for me..

I set one side of the swimming tank as inlet velocity, the opposite outlet side as static pressure ,

for the other sides of the tank as ideal wall, and the robot inside the tank as real wall.

I dont know if I am write or wrong.

please correct me.

I didn't work with Fluid simulation of solidworks. Normally the body of your robot should be wall like other walls that you have defined. The following link maybe help you:

https://www.youtube.com/watch?v=tMA3t9MrsGs

Farah, there are various turbulence models (K-omega, K-SST, RANS, Laminar models) depending on the application, you have to decide the best models for particular analysis.

Inlet- the entry of particular fluid say air or water at particular velocity or due to pressure difference (since fluid moves when there is velocity or pressure difference)

Outlet- the exit of the fluid to atmosphere or out of particular considered domain (under consideration)

I am not sure about ideal and real wall, but hope ideal wall must be stationary throughout the simulation whereas real wall will be moving or interacting with simulation.

Thank you very much

Farah, if your robot is going to perform swimming strokes, you need to set applicable moving wall conditions on the robot. And for the turbulence model, try using k-epsilon realizable or k-omega -SST.

k-epsilon is used when the turbulence is high and the flow seperation is minimal.

k-omega is applicable when the turbulence is low but you are expecting a flow separation