Describe the bugGive a clear and concise description of what the bug is and what you expect the behaviour to be instead. Please provide enough instructions and data for a developer to reproduce the problem (config, mesh, commands, etc.). Please provide the smallest working example that reproduces the problem.
Hi all,
I posted this on the CFD forum, and one of the members mentioned it may be a bug and post it here.
I am simulating flow over an inlet at hypersonic speeds (Mach 7) in 2D using the JST scheme. I have done a mesh convergence study with an inviscid simulation and the residuals go to machine accuracy for all the meshes and works fine.
I am using the Navier-Stokes solver for the viscous simulations. I have 5 meshes (very_coarse, coarse, medium, fine, very_fine) to do a mesh convergence study. The very_coarse (VC) and coarse (C) meshes converge to a residual rho of -8.5 and -9 with Cauchy on drag = -10 orders of magnitude. The finer meshes barely converge to -4 to -5, before increasing -2 where they plateau. For all of the meshes (including the converged VC and C), there is an abnormal region with a higher Mach number at the leading edge (11 for VC and 9 for C). Following one of the discussion on the CFD forum (https://www.cfd-online.com/Forums/su2/142261-anomalous-mach-number.html), I extended the domain around the leading edge, but that had no effect on this region.
I played around with the 2nd and 4th coefficients in the scheme; the 4th coefficient has not effect on this region. Increasing 2nd coefficient smooths discontinuities, so it decreases the Mach number in those regions but its still higher than freestream. Increasing the 2nd coefficient also makes the shock resolution in the rest of the flow field very smooth (looks like a smudge on the screen).
Is there a reason why this happens? I did a few first order upwind simulations; they converge almost instantly and the higher Mach region does not exist. Nor does it exist in 2nd order upwind scheme, but these dont converge any further than -4. I want to conduct optimisation, for which the JST scheme shows good stability and convergence for adjoint problems.
I have uploaded the config file, convergence history and images of the high Mach region around the leading edge here: https://drive.google.com/drive/folders/1HtBwS9rVuWn5IJoDpMCCpRyYehOTk9by?usp=drive_link. The history file also contains information of the meshes (number of cells and y+ values). I uploaded one of the converging meshes (v_coarse.su2) and one of the diverging meshes (medium.su2).
I used WEIGHTED_LEAST_SQUARES to help with the sharp edge; this decreases the Mach in the region but not by much (~9 for the very_coarse mesh). I have also run the RANS solver with JST, but there is no significant difference from using NS with WEIGHTED_LEAST_SQUARES; the Mach number in the region 8.74.
Thank you,
RK
Bug report checklistPlease make sure that you have followed the checklist below, many common problems can be solved by:
Describe the bug Give a clear and concise description of what the bug is and what you expect the behaviour to be instead. Please provide enough instructions and data for a developer to reproduce the problem (config, mesh, commands, etc.). Please provide the smallest working example that reproduces the problem.
Hi all,
I posted this on the CFD forum, and one of the members mentioned it may be a bug and post it here.
I am simulating flow over an inlet at hypersonic speeds (Mach 7) in 2D using the JST scheme. I have done a mesh convergence study with an inviscid simulation and the residuals go to machine accuracy for all the meshes and works fine.
I am using the Navier-Stokes solver for the viscous simulations. I have 5 meshes (very_coarse, coarse, medium, fine, very_fine) to do a mesh convergence study. The very_coarse (VC) and coarse (C) meshes converge to a residual rho of -8.5 and -9 with Cauchy on drag = -10 orders of magnitude. The finer meshes barely converge to -4 to -5, before increasing -2 where they plateau. For all of the meshes (including the converged VC and C), there is an abnormal region with a higher Mach number at the leading edge (11 for VC and 9 for C). Following one of the discussion on the CFD forum (https://www.cfd-online.com/Forums/su2/142261-anomalous-mach-number.html), I extended the domain around the leading edge, but that had no effect on this region.
I played around with the 2nd and 4th coefficients in the scheme; the 4th coefficient has not effect on this region. Increasing 2nd coefficient smooths discontinuities, so it decreases the Mach number in those regions but its still higher than freestream. Increasing the 2nd coefficient also makes the shock resolution in the rest of the flow field very smooth (looks like a smudge on the screen).
Is there a reason why this happens? I did a few first order upwind simulations; they converge almost instantly and the higher Mach region does not exist. Nor does it exist in 2nd order upwind scheme, but these dont converge any further than -4. I want to conduct optimisation, for which the JST scheme shows good stability and convergence for adjoint problems.
I have uploaded the config file, convergence history and images of the high Mach region around the leading edge here: https://drive.google.com/drive/folders/1HtBwS9rVuWn5IJoDpMCCpRyYehOTk9by?usp=drive_link. The history file also contains information of the meshes (number of cells and y+ values). I uploaded one of the converging meshes (v_coarse.su2) and one of the diverging meshes (medium.su2).
I used WEIGHTED_LEAST_SQUARES to help with the sharp edge; this decreases the Mach in the region but not by much (~9 for the very_coarse mesh). I have also run the RANS solver with JST, but there is no significant difference from using NS with WEIGHTED_LEAST_SQUARES; the Mach number in the region 8.74.
Thank you, RK
Bug report checklist Please make sure that you have followed the checklist below, many common problems can be solved by:
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