Learning Forum

[Paraskevas Kalandronis]

Hi, 

I 've been having an issue with my analysis on a torpedo and i really cant find the problem. First of all let me explain what i have been doing. I have a torpedo and i am using the 1/4 of the geometry since it's symmetrical. I have been following the tutorial of the solar car for the better part of this simulation. I created the enclosure and the wake in the geometry. I am going to the mesh and then again i follow the tutorial of the solar car of ansys (I am adding 2 local sizings body of influence for wake, and another one for the torpedo) then i have in the boundary types as wall the propellers (2 different labels) the body of the torpedo, as a symmetry the symmetry and sky (again as the tutorial) and the inlet as velocity inlet and the outlet as pressure outlet . I am adding boundary layers on fluid regions and they grow only on walls (smooth transition) and i am generating the volume mesh with polyhexcore. So far i dont have problems or i think i dont have. 

In the setup section i starting by picking the k-omega SST viscous model, stating that the operating pressure is 176644 Pa (i am assuming the torpedo is moving 7m underwater) , in the reference values i am adding the Area (i got it from the projected areas on the x-axis by choosing the whole torpedo) the density of water , the viscocity and the length of the torpedo. In the fluids i am using water-liquid.  At the boundary conditions i am putting on the inlet the speed, at the outlet i have the gauge pressure as zero. At the walls I have the propellers as a rotational wall with a given speed, the torpedo as a stationary wall-no slip and lastly the sky as a stationary wall with specified shear (0Pa x,y,z) . In the reports i am choosing drag coefficient and lift coefficient. In the drag coefficient reports i have negative values and i cant figure out why.

Can you share your input?

[Paraskevas Kalandronis]

well.... the vectors where wrong...lol...

[Rob]

:)  Oops.... Glad you got it sorted.