[emjaey3590]

Hello Foamers,

I am trying to use supersonic compressible solver (rhoCentralFoam/sonicFoam) to simulate flow across a bullet, which has a rotational motion (dynamicMeshDict). The bullet used is a stl file, henceforth I used snappyHexMesh to generate the Mesh. The arbitrary mesh interface (AMI) is also introduced in the simulation to enable simulation across disconnected, adjacent, mesh domains.

The boundary condition used for pressure (p) is:
For inlet, walls, bullet wall I have used "zeroGradient" boundary condition.
For outlet I have used "waveTransmissive" boundary condition.
For AMI I have used "cyclicAMI" boundary condition.

The boundary condition used for velocity (U) is:
For inlet "supersonicFreestream" is used.
For outlet "inletOutlet" is used.
For bullet "movingWallVelocity" is used.
For walls "zeroGradient" is used.
For AMI "cyclicAMI" is used.

The boundary condition used for temperature (T) is:
For inlet and outlet "inletOutlet" is used.
For walls and bullet wall "zeroGradient" is used.
For AMI "cyclicAMI" is used.

The fvSchemes and FvSolution that I have used is same as that of the tutorials that are provided for rhoCentralFoam and sonicFoam.

But when I try to launch the simulation, it runs for few iterations and finally fives the error mentioned below

--> FOAM FATAL ERROR: 
Negative initial temperature T0: -26.69115

    From function Foam::scalar Foam::species::thermo<Thermo, Type>::T(Foam::scalar, Foam::scalar, Foam::scalar, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar, Foam::scalar) const, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar, Foam::scalar) const, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar) const) const [with Thermo = Foam::hConstThermo<Foam::perfectGas<Foam::specie> >; Type = Foam::sensibleInternalEnergy; Foam::scalar = double; Foam::species::thermo<Thermo, Type> = Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleInternalEnergy>]
    in file /home/ubuntu/OpenFOAM/OpenFOAM-6/src/thermophysicalModels/specie/lnInclude/thermoI.H at line 54.

FOAM aborting

#0  Foam::error::printStack(Foam::Ostream&) at ??:?
#1  Foam::error::abort() at ??:?
#2  Foam::hePsiThermo<Foam::psiThermo, Foam::pureMixture<Foam::constTransport<Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleInternalEnergy> > > >::calculate() at ??:?
#3  Foam::hePsiThermo<Foam::psiThermo, Foam::pureMixture<Foam::constTransport<Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleInternalEnergy> > > >::correct() at ??:?
#4  ? in "/opt/openfoam6/platforms/linux64GccDPInt32Opt/bin/rhoCentralFoam"
#5  __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#6  ? in "/opt/openfoam6/platforms/linux64GccDPInt32Opt/bin/rhoCentralFoam"
^C
[1]+  Aborted                 (core dumped) rhoCentralFoam > log

Would somebody be kind enough to help me solve this problem.

[Jonathan]

Originally Posted by emjaey3590

Hello Foamers,

I am trying to use supersonic compressible solver (rhoCentralFoam/sonicFoam) to simulate flow across a bullet, which has a rotational motion (dynamicMeshDict). The bullet used is a stl file, henceforth I used snappyHexMesh to generate the Mesh. The arbitrary mesh interface (AMI) is also introduced in the simulation to enable simulation across disconnected, adjacent, mesh domains.

The boundary condition used for pressure (p) is:
For inlet, walls, bullet wall I have used "zeroGradient" boundary condition.
For outlet I have used "waveTransmissive" boundary condition.
For AMI I have used "cyclicAMI" boundary condition.

The boundary condition used for velocity (U) is:
For inlet "supersonicFreestream" is used.
For outlet "inletOutlet" is used.
For bullet "movingWallVelocity" is used.
For walls "zeroGradient" is used.
For AMI "cyclicAMI" is used.

The boundary condition used for temperature (T) is:
For inlet and outlet "inletOutlet" is used.
For walls and bullet wall "zeroGradient" is used.
For AMI "cyclicAMI" is used.

The fvSchemes and FvSolution that I have used is same as that of the tutorials that are provided for rhoCentralFoam and sonicFoam.

But when I try to launch the simulation, it runs for few iterations and finally fives the error mentioned below

--> FOAM FATAL ERROR: 
Negative initial temperature T0: -26.69115

    From function Foam::scalar Foam::species::thermo<Thermo, Type>::T(Foam::scalar, Foam::scalar, Foam::scalar, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar, Foam::scalar) const, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar, Foam::scalar) const, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar) const) const [with Thermo = Foam::hConstThermo<Foam::perfectGas<Foam::specie> >; Type = Foam::sensibleInternalEnergy; Foam::scalar = double; Foam::species::thermo<Thermo, Type> = Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleInternalEnergy>]
    in file /home/ubuntu/OpenFOAM/OpenFOAM-6/src/thermophysicalModels/specie/lnInclude/thermoI.H at line 54.

FOAM aborting

#0  Foam::error::printStack(Foam::Ostream&) at ??:?
#1  Foam::error::abort() at ??:?
#2  Foam::hePsiThermo<Foam::psiThermo, Foam::pureMixture<Foam::constTransport<Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleInternalEnergy> > > >::calculate() at ??:?
#3  Foam::hePsiThermo<Foam::psiThermo, Foam::pureMixture<Foam::constTransport<Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleInternalEnergy> > > >::correct() at ??:?
#4  ? in "/opt/openfoam6/platforms/linux64GccDPInt32Opt/bin/rhoCentralFoam"
#5  __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#6  ? in "/opt/openfoam6/platforms/linux64GccDPInt32Opt/bin/rhoCentralFoam"
^C
[1]+  Aborted                 (core dumped) rhoCentralFoam > log

Would somebody be kind enough to help me solve this problem.

Not sure if you solved this, but I have found with compressible simulations (rhoCentral and others) that time step size is really important. I often get (got) negative temperatures as soon as the shocks started forming if my Courant number was too high. Using adaptive time stepping based on Co number really helped, otherwise reducing the timestep to something smaller usually helps.

The other thing which people sometimes miss is to check your fluid properties - if you have an error and you try to do sonic flow, you're going to get funny results. For instance, make sure if you copy transportProperties / thermoPhysicalProperties from another case they are correct for your set up.

Hope it helps.

[ZakiLeon]

Hi everyone,

I have the very same issue with a simulation using NCC dynamic mesh methods (Updated version of ACMI), and I think it is related to the userTime configuration.

My model represents a piston engine. The piston movement is defined not directly by a time but by the crank angle. When I am using a rhoPimpleFoam sovler, everything works fine, (Delta theta = 0.1). But when I switch to a rhoCentralFoam solver, I need to greatly reduce the time step (1e-6). Moving the piston by a time step of 1e-6 degrees is not releastic, which means that I need to switch back to a userTime defining a time and not a crank angle.

Does anyone know if it's possible to use userTime Engine and rhoCentralFoam at the same time ?