Preconditioning for multicomponent flows #2426

Cristopher-Morales · 2025-01-18T11:31:19Z

Proposed Changes

This pull request aims to extend the preconditioning for incompressible multicomponent flows, specifically when FLUID_MIXTURE model is used and energy equation is solved. Changes introduced in this pull request aim to solve directly for the sensible enthalpy instead of temperature. Specifically, the energy equation that is going to be solved for multicomponent flows is given as follows:

and the sensible enthalpy is:

Currently $C_{p}$ does not depend on temperature for FLUID_MIXTURE, but it depends on the mixture composition. So the sensible enthalpy simplifies to $C_{p}*(T-T_{0})$. For problems where $C_{p}$ strongly depends on the temperature, Cantera library will be coupled to SU2. After this pull request is completed, a pull request with a fluid model using Cantera will be done where an energy equation for the total enthalpy will be solved.
A PDF document containing further details about this pull request is available at the following link:
preconditioning_general_approach.pdf

Related Work

Currently fluid mixture does not work correctly when the energy equation is on, this is mainly due to the fact that the energy equation that must be solved for multicomponent flows is the one mentioned above for the sensible enthalpy and not the energy equation for a perfect gas that is currently solved in SU2.

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.

SU2_CFD/src/solvers/CIncEulerSolver.cpp

SU2_CFD/src/solvers/CIncNSSolver.cpp

SU2_CFD/include/fluid/CFluidModel.hpp

SU2_CFD/include/fluid/CFluidScalar.hpp

SU2_CFD/include/solvers/CFVMFlowSolverBase.inl

SU2_CFD/src/fluid/CFluidScalar.cpp

SU2_CFD/src/numerics/CNumerics.cpp

SU2_CFD/src/numerics/flow/convection/fds.cpp

Co-authored-by: Nijso <[email protected]>

pcarruscag · 2025-10-23T14:00:20Z

SU2_CFD/include/fluid/CFluidScalar.hpp

+  const su2double Ref_Temperature;        /*!< \brief Reference temperature. */
  const su2double GasConstant_Ref;        /*!< \brief Gas constant reference needed for Nondimensional problems. */
  const su2double Prandtl_Number;         /*!< \brief Prandlt number.*/
+  const su2double Schmidt_Turb_Number;         /*!< \brief Prandlt number.*/


Hi!

Thanks for your comment,

I have added the right documentation,

please let me know any additional comment/suggestion about it.

Thanks in advance!!

pcarruscag · 2025-10-23T14:03:31Z

SU2_CFD/include/numerics/flow/flow_sources.hpp

  viscous,       /*!< \brief Viscous incompressible flows. */
-  energy;        /*!< \brief computation with the energy equation. */
+  energy,        /*!< \brief computation with the energy equation. */
+  multicomponent; /*!< \brief multicomponent incompressible flows. */


Not needed anymore?

Hi!

thanks for you comment,

I added that boolean multicomponent because for axisymmetric flows, there is an additional term that comes from the enthalpy diffusion which is only needed for multicomponent flows (term in blue)

I thought that It should only be computed and added when it is needed because when the FLUID_MODEL is different than FLUID_MIXTURE, the species mass fractions become passive scalars, so the term in blue becomes zero.

Please let me know what you think about it.

Thank you so much in advance!!!

pcarruscag · 2025-10-23T14:03:55Z

SU2_CFD/include/numerics/flow/flow_diffusion.hpp

  su2double Mean_Thermal_Conductivity; /*!< \brief Mean value of the effective thermal conductivity. */
+  su2double Mean_Heat_Capacity;        /*!< \brief Mean value of the heat capacity. */


Can we avoid intermediate su2doubles as class members?

Hi!

Thanks for the comment!

I have removed this line because with the previous pull request about conductivity for compressible flows #2420, the mean heat capacity is now a member of the CAvgGrad_Base in the flow_diffussion.hpp, so there was no need to re-declare it in the CAvgGradInc_Flow.
Please let me know any additional comment about it.

Thanks in advance!!

pcarruscag · 2025-10-23T14:04:49Z

SU2_CFD/include/solvers/CIncEulerSolver.hpp

+   * \param[in,out] primitive - Primitive variables.
+   * \param[in] scalar - scalar variable.


order doesn't match function signature

HI!

Thanks for the comment!

I switched the order of them according to the function.

Please let me know if that was needed to address this comment.

Thanks in advance!!!

pcarruscag · 2025-10-23T14:06:58Z

SU2_CFD/src/fluid/CFluidFlamelet.cpp

+void CFluidFlamelet::SetTDState_h(su2double val_enthalpy, const su2double* val_scalars) {
+  SetTDState_T(val_enthalpy, val_scalars);
+}
+


This looks comment-worthy, why can you pass enthalpy as temperature?

Hi!

thanks for the comment!!,

when the SPECIES_FLAMELET solver is used, one of the scalar equation is for total enthalpy, specifically the one with index 1.
As you can see from the picture in SetTDState_T added by Nijso and Evert, if I am not mistaken, the temperature (which is the current variable that is being solved in SU2) is a passive value, it is not used in that function because with the val_scalars (which are the variables used in the manifold for the Flamelet generated Manifold (FGM) approach) the temperature and any other thermochemical property are retrieved from the lookup table as you can see from lines 131.

So, as you might remember, in a previous developer meeting I mentioned that if we solve for the enthalpy in the preconditioning, we can eventually move the enthalpy equation solved in the SPECIES FLAMELET solver to the INC_EULER_SOLVER. This is not done in the current pull request because then the pull request will become even much larger as it is.
Please let me know if I should add a comment above these two functions explaining why enthalpy and temperature are passive values when the SPECIES_FLAMELET solver is used.

In a future pull request, we plan to move the enthalpy equation to the INC_EULER_SOLVER, so the SPECIES_FLAMELET solver can be reduced and used only for solving the additional transport equations needed for the FGM approach.

Thank you so much in advance!!!

pcarruscag · 2025-10-23T14:09:44Z

SU2_CFD/include/fluid/CFluidScalar.hpp


+  /*!
+   * \brief Get enthalpy diffusivity terms.
+   */


document the arguments, what size is the array expected to have, etc.

Hi!

Thank you so much for your comment,

I have added a documentation of arguments and the size of the array expected by this function.

Please let me know what you think about it.

Thanks!

SU2_CFD/include/variables/CIncEulerVariable.hpp

SU2_CFD/src/numerics/flow/convection/centered.cpp

pcarruscag · 2025-10-23T14:26:16Z

SU2_CFD/src/solvers/CIncNSSolver.cpp

+  su2double EnthalpyDiffusion_i[MAXNVAR_SPECIES]{0.0};
+  su2double GradEnthalpyDiffusion_i[MAXNVAR_SPECIES]{0.0};
+  FluidModel->SetTDState_T(nodes->GetPrimitive(iPoint)[prim_idx.Temperature()], Species_i);
+  FluidModel->SetEddyViscosity(nodes->GetPrimitive(iPoint)[prim_idx.EddyViscosity()]);
+  FluidModel->GetEnthalpyDiffusivity(EnthalpyDiffusion_i);
+  if (implicit) FluidModel->GetGradEnthalpyDiffusivity(GradEnthalpyDiffusion_i);
+
+  /*--- Repeat the above computations for jPoint. ---*/
+
+  su2double EnthalpyDiffusion_j[MAXNVAR_SPECIES]{0.0};
+  su2double GradEnthalpyDiffusion_j[MAXNVAR_SPECIES]{0.0};
+  FluidModel->SetTDState_T(nodes->GetPrimitive(jPoint)[prim_idx.Temperature()], Species_j);
+  FluidModel->SetEddyViscosity(nodes->GetPrimitive(jPoint)[prim_idx.EddyViscosity()]);
+  FluidModel->GetEnthalpyDiffusivity(EnthalpyDiffusion_j);
+  if (implicit) FluidModel->GetGradEnthalpyDiffusivity(GradEnthalpyDiffusion_j);


use a lambda to avoid the copy paste

Hi!

Thank you so much for your comment,

I have added the lambda function for this part.

Please let me know what you think about it.

Thanks!

SU2_CFD/src/solvers/CIncNSSolver.cpp

Co-authored-by: Pedro Gomes <[email protected]>

bigfooted · 2025-11-03T21:07:08Z

Hi @Cristopher-Morales , do the pywrapper testcases work correctly or is there still some issue?

Cristopher-Morales · 2025-11-04T13:26:24Z

Hi @Cristopher-Morales , do the pywrapper testcases work correctly or is there still some issue?

Hi @bigfooted,

Thanks for your comment!!

the test case pywrapper_zimont does not work correctly, the other one regarding custom source buoyancy works fine.
Could you share with me information about this test case?
so I can see the energy equation that is used for this test case.
It might need some additional adaption this test case.

Thank you so much in advance!!!

Cristopher-Morales and others added 22 commits October 22, 2024 13:43

solving for enthalpy

ca9083e

fixing flux jacobian

0487a68

Merge branch 'develop' into feature_preconditioning

dd369bb

fix output error

5076f9d

adding enthalpy diffusion

09fe6f4

Merge branch 'develop' into feature_preconditioning

851b13f

moving enthalpy diffusion terms to CIncNSSolver.cpp

f258308

small fix

63a8f37

Merge branch 'develop' into feature_preconditioning

cb1d3ef

cleaning and rewritting some functions

30d0b88

Merge branch 'develop' into feature_preconditioning

dd22fcd

axisymetric source term and corrected flux jacobian at the wall

7f92730

updating BC_ConjugateHeat_Interface for fluid mixture

fdbb9b9

Merge branch 'develop' into feature_preconditioning

c0b10a6

Merge branch 'develop' into feature_preconditioning

911c996

activating muscl, consistent extrapolation for multicomponent

2af10c3

Merge branch 'develop' into feature_preconditioning

d0d0221

correct average enthalpy for multicomponent flows output

a1f526c

Merge branch 'develop' into feature_preconditioning

c469d32

changing boolean names

ef2dc5f

up to date to develop

94bd0b0

Merge branch 'develop' into feature_preconditioning

1c44044

Cristopher-Morales added the changelog:feature label Jan 18, 2025

Cristopher-Morales changed the title ~~[WIP] Preconditioning fro multicomponent flows~~ [WIP] Preconditioning for multicomponent flows Jan 18, 2025

github-advanced-security bot found potential problems Jan 18, 2025

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SU2_CFD/src/solvers/CIncEulerSolver.cpp Fixed Show fixed Hide fixed

SU2_CFD/src/solvers/CIncNSSolver.cpp Fixed Show fixed Hide fixed

Cristopher-Morales added 2 commits January 18, 2025 14:12

adding brackets

912642b

fixing warning

a6ce2d4

pcarruscag requested changes Jan 19, 2025

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Cristopher-Morales added 2 commits January 23, 2025 10:01

Merge branch 'develop' into feature_preconditioning

e9d1e1f

Merge branch 'develop' into feature_preconditioning

127df29

Cristopher-Morales and others added 12 commits October 9, 2025 16:29

Update SU2_CFD/include/numerics/flow/convection/centered.hpp

e8f9571

Co-authored-by: Nijso <[email protected]>

Update SU2_CFD/include/numerics/flow/convection/centered.hpp

66de4bc

Co-authored-by: Nijso <[email protected]>

Merge branch 'develop' into feature_preconditioning

bae602b

adding eddy diffusivity in enthalpy diffusion

b051888

Merge branch 'develop' into feature_preconditioning

5a14508

updating residuals species transport

f990a55

updating residuals

9224935

update residual and fixing output temperature

051c201

small cleaning

07b3f61

updating residuals

63a8761

updating residuals

42d3e9b

updating residuals DAspecies tutorial case

3491b37

Cristopher-Morales mentioned this pull request Oct 23, 2025

Updating files for preconditioning pull request su2code/Tutorials#69

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pcarruscag reviewed Oct 23, 2025

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Cristopher-Morales and others added 13 commits October 24, 2025 16:25

Merge branch 'develop' into feature_preconditioning

9a8d01e

Merge branch 'develop' into feature_preconditioning

341281b

Update SU2_CFD/include/variables/CIncEulerVariable.hpp

13985c5

Co-authored-by: Pedro Gomes <[email protected]>

Update SU2_CFD/src/fluid/CFluidScalar.cpp

8cffbd2

Co-authored-by: Pedro Gomes <[email protected]>

addressing comments part 1

e5c3992

Update SU2_CFD/src/solvers/CIncNSSolver.cpp

a2ae0b1

Co-authored-by: Pedro Gomes <[email protected]>

addressing comments part 2

21fab1a

addressing comments part 3

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Merge branch 'develop' into feature_preconditioning

b8ecc10

Merge branch 'develop' into feature_preconditioning

2177d51

Merge branch 'develop' into feature_preconditioning

fed3aa2

updating residuals

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updating residuals and .ref files

2e0dcfe

updating residual custom_source_buoyancy

fa3bad1

		su2double Mean_Thermal_Conductivity; /!< \brief Mean value of the effective thermal conductivity. /
		su2double Mean_Heat_Capacity; /!< \brief Mean value of the heat capacity. /

		* \param[in,out] primitive - Primitive variables.
		* \param[in] scalar - scalar variable.

Preconditioning for multicomponent flows #2426

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Preconditioning for multicomponent flows #2426

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Cristopher-Morales commented Jan 18, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Cristopher-Morales Oct 27, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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bigfooted commented Nov 3, 2025

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Cristopher-Morales commented Nov 4, 2025

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Cristopher-Morales commented Jan 18, 2025 •

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