[WIP] Pressure Based Solver by thijsaalbers · Pull Request #2812 · su2code/SU2

thijsaalbers · 2026-05-07T13:05:07Z

Proposed Changes

The current work aims at getting a working version of the pressure based incompressible flow solver into the development branch.

Investigation

Identify major changes between latest SU2 version (8.5.0) and the previous attempts (v6/v7) which could cause implementation issues
Resolve issues present in the previous attempts (see Related Work)

Implementation (in order of priority)

Implement general structure i.e. driver/iterator/solver
Adapt the old numerics / solver details to modern SU2 coding standards.

Validation and Maintenance

Validation and Verification
Documentation, Tutorials etc.

Current Issues

Numerics are currently taken directly from previous attempts. This means they are not yet up to date with the current implementation. Work on this should involve existing scalar flux to avoid duplication of upwinding. Central flux could be moved to centered.*pp for consistency with the current centered schemes for density based methods.
Current flux in numerics is only upwinding and does not consider Rhie-Chow interpolation. The location of the implementation of Rhie-Chow in previous attempts is (currently) not yet investigated, it should be investigated if the Rhie-Chow interpolation can be moved to the flux computation for better separation of concerns.

Related Work

This work is based on earlier attempts by Nitish Anand (2024) and Akshay Koodly (2021), see feature branches feature_PBFlow_V8 and feature_Pressure_based respectively. Also see PR #2210

PR Checklist

I am submitting my contribution to the develop branch.
My contribution generates no new compiler warnings (try with --warnlevel=3 when using meson).
My contribution is commented and consistent with SU2 style (https://su2code.github.io/docs_v7/Style-Guide/).
I used the pre-commit hook to prevent dirty commits and used pre-commit run --all to format old commits.
I have added a test case that demonstrates my contribution, if necessary.
I have updated appropriate documentation (Tutorials, Docs Page, config_template.cpp), if necessary.

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CodeQL found more than 20 potential problems in the proposed changes. Check the Files changed tab for more details.

pcarruscag · 2026-05-09T22:21:20Z

Please think about ways of reusing the numerics used by the scalar solvers, not duplicating code is part of the criteria for merging PRs.

pcarruscag · 2026-05-09T22:22:48Z

+  Diff_U = new su2double [nVar];
+  Velocity_i = new su2double [nDim];
+  Velocity_j = new su2double [nDim];
+  Velocity_upw = new su2double [nDim];
+  MeanVelocity = new su2double [nDim];
+  Flux = new su2double [nDim];
+  ProjFlux_i = new su2double [nVar];
+  ProjFlux_j = new su2double [nVar];
+  Jacobian_i = new su2double* [nVar];
+  Jacobian_j = new su2double* [nVar];
+  Jacobian_upw = new su2double* [nVar];
+
+  for (iVar = 0; iVar < nVar; iVar++) {
+    Jacobian_i[iVar] = new su2double [nVar];
+    Jacobian_j[iVar] = new su2double [nVar];
+    Jacobian_upw[iVar] = new su2double [nVar];


Please look at more recent examples of introducing new numerics classes or cleaning old ones, this is not the way for new code.

pcarruscag · 2026-05-09T22:27:51Z

+  Face_Flux = 0.0;
+  for (iDim = 0; iDim < nDim; iDim++) {
+    Velocity_i[iDim] = V_i[iDim+1];
+    Velocity_j[iDim] = V_j[iDim+1];
+    MeanVelocity[iDim] =  0.5*(Velocity_i[iDim] + Velocity_j[iDim]);
+    Face_Flux += MeanDensity*MeanVelocity[iDim]*Normal[iDim];
+  }


This is not a correct implementation of Rhie-Chow momentum interpolation.
Please consider attending a developer meeting to explain your plans with this PR, the way I see it going, it's not going to make the cut to merge into develop.

Thanks for your feedback. I will let you know when it is ready for review.

Ok. Keep in mind that we prefer many small PRs over one big one. This way, lessons learned from one review carry over to the next small PR.
Very large PRs tend to take a long time to review because the authors tend to run out of time rather than finish the work.
https://su2code.github.io/docs_v7/Code-Review/

@thijsaalbers please discuss with @vdweide if there can be a 'minimum example' PR of the implementation, one that can be delivered half-way in this GSOC project. Then add 'nice to have' features later.
For announcements on developer meetings and also for quick questions, please check slack.

We should discuss architecture at a developers meeting... I'm getting dejavu 😅

Implements the full class structure required for the pressure-based solver in a minimal form. The code compiles and runs but does not yet contain any numerical/physical implementation. Future work will focus on implementing solver logic. Note: In the previous attempts (see related work) there is noticeable code duplication between CIncEuler and CPBIncEuler. The final architecture may be revised depending on how the implementation of CPBIncEuler evolves.

+  /*--- Store the number of vertices on each marker for deallocation later ---*/
+
+  nVertex.resize(nMarker);
+  for (iMarker = 0; iMarker < nMarker; iMarker++)


+      // numerics[iMGlevel][POISSON_SOL][visc_term] = new CAvgGrad_Poisson(nDim, nVar_Poisson, config);
+
+    /*--- Assign the convective boundary term as well to account for flow BCs as well --*/
+    for (iMGlevel = 0; iMGlevel <= config->GetnMGLevels(); iMGlevel++) {


+  //GetFluidModel()->SetTDState_T(Temperature_Inf, scalar_init);
+  //Enthalpy_Inf = GetFluidModel()->GetEnthalpy();


+  /*--- Perform the non-dimensionalization for the flow equations using the
+   specified reference values. ---*/
+
+  // SetNondimensionalization(config, iMesh);


+      // numerics[iMGlevel][POISSON_SOL][source_first_term] = new CSource_PoissonFVM(nDim, nVar_Poisson, config);
+      // numerics[iMGlevel][POISSON_SOL][source_second_term] = new CSourceNothing(nDim, nVar_Poisson, config);


+            switch (config->GetKind_Centered_Flow()) {
+              case CENTERED::CDS : /* numerics[MESH_0][FLOW_SOL][conv_term] = new CCentPB_Flow(nDim, nVar_Flow, config); */ break;
+              default:
+                SU2_MPI::Error("Invalid centered scheme or not implemented.\n Currently, only CDS is available for pressure based incompressible flows.", CURRENT_FUNCTION);

+            }


+   * \brief Get the temperature of the point.
+   * \return Value of the temperature of the point.
+   */
+  // inline su2double GetTemperature(unsigned long iPoint) const final { return Solution(iPoint, 0); }


+  /*
+   * \brief Destructor of the class.
+   */
+  // ~CPoissonSolver(void);


+  /*!
+   * \brief Constructor of the class.
+   */
+  // CPoissonSolver(void);


+  /*!
+   * \brief Constructor of the class.
+   */
+  //CPBIncEulerSolver(CGeometry *geometry, CConfig *config, unsigned short iMesh) {};


Initial configuration options and a test case

64d4213

thijsaalbers self-assigned this May 7, 2026

thijsaalbers added PR: draft changelog:feature GSoC Google Summer of Code labels May 7, 2026

Numerics and driver additions, WIP

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github-advanced-security AI found potential problems May 9, 2026

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pcarruscag reviewed May 9, 2026

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thijsaalbers added 2 commits May 12, 2026 13:24

Remove outdated numerics

8d0bcf9

github-advanced-security AI found potential problems May 12, 2026

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[WIP] Pressure Based Solver#2812

[WIP] Pressure Based Solver#2812
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feature_pressure_based_2026

thijsaalbers commented May 7, 2026 •

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		//GetFluidModel()->SetTDState_T(Temperature_Inf, scalar_init);
		//Enthalpy_Inf = GetFluidModel()->GetEnthalpy();

		// numerics[iMGlevel][POISSON_SOL][source_first_term] = new CSource_PoissonFVM(nDim, nVar_Poisson, config);
		// numerics[iMGlevel][POISSON_SOL][source_second_term] = new CSourceNothing(nDim, nVar_Poisson, config);

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Proposed Changes

Investigation

Implementation (in order of priority)

Validation and Maintenance

Current Issues

Related Work

PR Checklist

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thijsaalbers commented May 7, 2026 •

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