March 19, 2021 at 10:06 pmrupatelSubscriberI have solved a cavitation mixture model with laminar, translating the wall (flow direction) for 3d geometry. Its a flow between nonconformal contacting bodies. nI checked each term of Navier Stokes equation on streamline and equating addition of inertia to Pressure and viscous forces. I am getting errors near-wall boundary. However, if streamline is at the fluid domain the inertia forces are equal to generated pressure and viscous forces, but near solid wall its not. ncan someone tell me why is this difference, as my solution has converged fully, this means it should solve the Navier stokes equation completely and should not give me any residual as it not giving on the fluid domain, but its giving an error near the solid wall?.
March 22, 2021 at 1:01 pmKarthik RAdministratorHello,nHow are you checking the convergence only near the wall? What do you mean by as my solution has converged fully, this means it should solve the Navier stokes equation completely and should not give me any residual as it not giving on the fluid domain, but its giving an error near the solid wall?nCould you provide some screenshots to help us understand this better?nKarthikn
March 22, 2021 at 1:27 pmrupatelSubscriberwhen I see the Scaled residual(Continuity, x,y,z, velocity) in fluent, it converged. And I also plotted the convergence history of the Maximum pressure, which also started becoming constant after 500 iterations. On the basis of these plots generated by fluent, I consider my results have converged. Now, I export all solution data to CFD post-processing and trying to subtract inertia forces (L.H.S of the above equation) with RHS, which is the simplified form of Navier stokes equation according to my model, after applying the assumption. And checking results on the streamline. which is passing near the solid (red). I should get 0 similar to the blue line.
March 22, 2021 at 1:53 pmrupatelSubscriberHi Karthik, nIt may be possible, that I am wrong. I want to check that on the streamline the Navier Stokes (NS) equation's which term is responsible for pressure generation in X direction. and what is the numerical value of that cause. before doing that I wanted to check that the mathematical expression of the NS equation is true on the streamline or not. According to me it should be true and I should get zero when I subtract LHS with RHS, but I can not see this through my simulation results. nIf you cannot understand anything that I explained above. Then, My simple question is as followingnhow i can assure that the simulation I am doing is correct. nI don't have any experimental data for comparison, of my results. Therefore, I want to be very sure about the simulation results are correct.nCould you please let me know. nThank you for your response n
March 22, 2021 at 2:42 pmDrAmineAnsys Employee1/By doing Verification and Validation studiesn2/If you cannot validate you need at least to quantify numerical errors (there are a lot of roots) and evaluate the results by searching for some well known correlations, formulas, data,...nnWhat I have understood is that you want to validate the discretized transport equations term by term. This first of all will be hard as you required the raw data coming from the integrated equations for each control volume. Again if the red line is the one near the wall you might check if you are resolving the near wall regions reasonably too.n
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