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Fix gradient handling for viscous fluxes #4

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Fix gradient handling for viscous fluxes #4

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356811b
Bugfix: use unlimited gradients for viscous fluxes
hheinzer Dec 10, 2025
f3a6462
Bugfix: boundary-face gradients for viscous fluxes
hheinzer Dec 10, 2025
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6 changes: 4 additions & 2 deletions src/mesh/mesh_vars.f90
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Expand Up @@ -83,8 +83,10 @@ MODULE MOD_Mesh_Vars
REAL :: pvar(NVAR) ! Primitive Variables
REAL :: cvar(NVAR) ! Conservative Variables
REAL :: cvar_stage(NVAR) ! Conservative Variables at initial RK stage (needed for 2nd order RK time stepping)
REAL :: u_x(NVAR) ! x-gradient of pvar
REAL :: u_y(NVAR) ! y-gradient of pvar
REAL :: u_x(NVAR) ! x-gradient of pvar (limited for convection)
REAL :: u_y(NVAR) ! y-gradient of pvar (limited for convection)
REAL :: u_x_unlim(NVAR) ! unlimited x-gradient (for viscous terms)
REAL :: u_y_unlim(NVAR) ! unlimited y-gradient (for viscous terms)
REAL :: u_t(NVAR) ! t-gradient of pvar
REAL :: source(NVAR) ! source term
REAL :: dt ! Cell timestep
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9 changes: 7 additions & 2 deletions src/navierstokes/flux/fluxcalculation.f90
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Expand Up @@ -83,8 +83,13 @@ SUBROUTINE FluxCalculation()
!-----------------------------------------------------------------------------------------------------------------------------------
! Extract left and right gradient
state_mean(:) = 0.5*(aSide%connection%pvar(:) + aSide%pvar(:) )
grad_Uxmean(:) = 0.5*(aSide%Elem%u_x(:)+aSide%connection%Elem%u_x(:))
grad_Uymean(:) = 0.5*(aSide%Elem%u_y(:)+aSide%connection%Elem%u_y(:))
IF (ASSOCIATED(aSide%connection%BC)) THEN ! the side is a boundary side
grad_Uxmean(:) = aSide%Elem%u_x_unlim(:)
grad_Uymean(:) = aSide%Elem%u_y_unlim(:)
ELSE
grad_Uxmean(:) = 0.5*(aSide%Elem%u_x_unlim(:)+aSide%connection%Elem%u_x_unlim(:))
grad_Uymean(:) = 0.5*(aSide%Elem%u_y_unlim(:)+aSide%connection%Elem%u_y_unlim(:))
END IF
BaryBary(:) = aSide%BaryBaryVec(:)/aSide%BaryBaryDist
correction(:) = (grad_Uxmean(:)*BaryBary(1) + grad_Uymean(:)*BaryBary(2) - &
(aSide%connection%Elem%pvar(:)-aSide%Elem%pvar(:))/aSide%BaryBaryDist)
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14 changes: 13 additions & 1 deletion src/reconstruction/reconstruction.f90
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Expand Up @@ -56,6 +56,8 @@ SUBROUTINE SpatialReconstruction(time)
aSide => aElem%firstSide
aElem%u_x(:) = 0
aElem%u_y(:) = 0
aElem%u_x_unlim(:) = 0
aElem%u_y_unlim(:) = 0
aElem%u_t(:) = 0
DO WHILE(ASSOCIATED(aSide))
aSide%pVar(:) = aElem%pVar(:)
Expand All @@ -74,6 +76,8 @@ SUBROUTINE SpatialReconstruction(time)
aElem => Elems(iElem)%Elem
aElem%u_x(:) = 0
aElem%u_y(:) = 0
aElem%u_x_unlim(:) = 0
aElem%u_y_unlim(:) = 0
aElem%u_t(:) = 0
END DO
!$omp end parallel do
Expand Down Expand Up @@ -125,6 +129,15 @@ SUBROUTINE SpatialReconstruction(time)
! END DO
! !$omp end parallel do

! Save unlimited gradients before limiting
!$omp parallel do private(aElem)
DO iElem = 1, nElems
aElem => Elems(iElem)%Elem
aElem%u_x_unlim = aElem%u_x
aElem%u_y_unlim = aElem%u_y
END DO
!$omp end parallel do

!-----------------------------------------------------------------------------------------------------------------------------------
!$omp parallel do private(aElem,aSide,dx,dy)

Expand All @@ -151,4 +164,3 @@ SUBROUTINE SpatialReconstruction(time)
END SUBROUTINE SpatialReconstruction

END MODULE MOD_Reconstruction