Altair SimLab CFD Simulation Residual Convergence Plot do not Converge HELP PLS!
I am currently conducting my thesis for context the study would only be focused on the Turbine Blade Enclosure of an Archimedes Screw Turbine and determining the velocity of the fluid body (water) entering the geometrical structure. So it would be without the presence of the actual turbine blade so no rotating elements or structures. I tried setting up the parameters that I think would be relevant for my desired results which is only the velocity of the fluid, however when I ran the solver and plotted the convergence for the residuals there is no convergence within the variables such as velocity and pressure. I would like to ask for help from the CFD community on what other set-up parameters that are lacking or are incorrect which caused my convergence plot to be inaccurate or wrong. Help me please Altair CFD community my thesis defense is coming up already im so lost 
I have attached my initial set-up parameters and other relevant information on the link. Thankyou so much guys!! https://imgur.com/a/snSu7bn
Best Answer
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quasar said:
Thankyou for your response and information! Another concern I have though is whenever the time step would increase to around 100 time step for other model iterations which mainly involve increasing the diameter of the inlet at an increment. The eddy frequency and the kinetic energy residual plot graph stays in between 0.1 and 0.01. However, the pressure and velocity plot would still fall below the 0.001 ratio. With that I would like to ask if all of the set up I made in terms of the boundary conditions, meshes, and other relevant set up parameters and values I set are correct or do I still need to make changes and tweaks towards my set-up in SimLab. Thankyou again!
Yes - It is quite possible you'll need to modify the meshing parameters, etc, as the model geometry or other simulation conditions changes.
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Altair EmployeeAnswers
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Please attach the relevant files/information directly to this post, rather than an outside link. Maybe some pictures of your setup showing BC locations, the input and Log files, etc.
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acupro_21778 said:
Please attach the relevant files/information directly to this post, rather than an outside link. Maybe some pictures of your setup showing BC locations, the input and Log files, etc.
Hello sorry for the external Link here are the images of my set-up. Thank you for your response!
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quasar said:
Hello sorry for the external Link here are the images of my set-up. Thank you for your response!
The residuals plot looks good to me - if that is the point at which the solver stopped automatically. By default, with convergence tolerance 1.e-3, the pressure and velocity residuals would need to be below 1.e-3, which they are. And the turbulence (kinetic energy and eddy frequency) would need to be below 1.e-2, which they are.
Similarly - for solution ratio plots - pressure and velocity should be below 1.e-2, and turbulence quantities below 1.e-1. Those all appear to be satisfied - from the images on this and the other (duplicate) ticket.
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acupro_21778 said:
The residuals plot looks good to me - if that is the point at which the solver stopped automatically. By default, with convergence tolerance 1.e-3, the pressure and velocity residuals would need to be below 1.e-3, which they are. And the turbulence (kinetic energy and eddy frequency) would need to be below 1.e-2, which they are.
Similarly - for solution ratio plots - pressure and velocity should be below 1.e-2, and turbulence quantities below 1.e-1. Those all appear to be satisfied - from the images on this and the other (duplicate) ticket.
Thankyou for your response and information! Another concern I have though is whenever the time step would increase to around 100 time step for other model iterations which mainly involve increasing the diameter of the inlet at an increment. The eddy frequency and the kinetic energy residual plot graph stays in between 0.1 and 0.01. However, the pressure and velocity plot would still fall below the 0.001 ratio. With that I would like to ask if all of the set up I made in terms of the boundary conditions, meshes, and other relevant set up parameters and values I set are correct or do I still need to make changes and tweaks towards my set-up in SimLab. Thankyou again!
0 -
quasar said:
Thankyou for your response and information! Another concern I have though is whenever the time step would increase to around 100 time step for other model iterations which mainly involve increasing the diameter of the inlet at an increment. The eddy frequency and the kinetic energy residual plot graph stays in between 0.1 and 0.01. However, the pressure and velocity plot would still fall below the 0.001 ratio. With that I would like to ask if all of the set up I made in terms of the boundary conditions, meshes, and other relevant set up parameters and values I set are correct or do I still need to make changes and tweaks towards my set-up in SimLab. Thankyou again!
Yes - It is quite possible you'll need to modify the meshing parameters, etc, as the model geometry or other simulation conditions changes.
1