Understanding NL Residuals in Simvascular History File and Setting Simulation Tolerance
Posted: Mon Apr 29, 2024 2:23 am
Hello everyone,
I've been working with Simvascular and examining the history.dat file generated from a steady simulation using the SV solver. As documented, the third column of the table represents the NL residuals. However, I'm struggling to grasp what exactly these residuals refer to: are they considered rms residuals or max residuals? I think that the distinction is crucial as it affects the interpretation of their values.
Furthermore, I've noticed instances where there are two rows with the same time step number, with the second residual being smaller than the first. I believe this indicates convergence, but I'm puzzled as to why not all rows exhibit this behavior. Could this dual residual be a result of the two iterations I've set? If so, shouldn't all time steps have two residuals? Additionally, I've observed cases where the residuals in rows with only one residual are higher than those with two, suggesting that the solver hasn't settled for that value.
Another aspect I'm uncertain about is what these residuals specifically refer to. Are they a combination of residuals from continuity and momentum equations? Shouldn't there be at least one for the continuity equation and one for the momentum equations in the x, y, and z directions?
Lastly, I'm curious about how to set the tolerance for the simulation. Is there a method within Simvascular to define this tolerance, and if so, could someone please guide me through the process?
Your insights and guidance on these matters would be greatly appreciated. Thank you in advance for your assistance!
Best regards,
Flaminia
I've been working with Simvascular and examining the history.dat file generated from a steady simulation using the SV solver. As documented, the third column of the table represents the NL residuals. However, I'm struggling to grasp what exactly these residuals refer to: are they considered rms residuals or max residuals? I think that the distinction is crucial as it affects the interpretation of their values.
Furthermore, I've noticed instances where there are two rows with the same time step number, with the second residual being smaller than the first. I believe this indicates convergence, but I'm puzzled as to why not all rows exhibit this behavior. Could this dual residual be a result of the two iterations I've set? If so, shouldn't all time steps have two residuals? Additionally, I've observed cases where the residuals in rows with only one residual are higher than those with two, suggesting that the solver hasn't settled for that value.
Another aspect I'm uncertain about is what these residuals specifically refer to. Are they a combination of residuals from continuity and momentum equations? Shouldn't there be at least one for the continuity equation and one for the momentum equations in the x, y, and z directions?
Lastly, I'm curious about how to set the tolerance for the simulation. Is there a method within Simvascular to define this tolerance, and if so, could someone please guide me through the process?
Your insights and guidance on these matters would be greatly appreciated. Thank you in advance for your assistance!
Best regards,
Flaminia