Mass source for simpleFoam-style solvers

timbojones · December 15, 2017, 00:05

Hello everyone,

I've implemented a mass source term and an associated momentum source term in simpleFoam to simulate a nozzle injection that I don't want to resolve on the grid. The mass source is implemented as a source in pEqn and the momentum source in UEqn. The sources are set via custom fields and explicit source terms in these equations.

I'd like to accomplish the same task using fvOptions. For the momentum source, implementation is very straightforward. However, to my understanding, the mass source should show up in pEqn, but it's not a pressure source. That is it's not a semiImplicitScalarSource on field(p).

My question is this. Has anyone implemented a mass source in simpleFoam using fvOptions? Alternatively, if you've done it as custom solver with source in pEqn, is there a trick to getting this to work smoothly? Any help or sharing would be greatly appreciated!

TimboJones

benjamintu · April 13, 2018, 04:52

hey timbo, trying more or less the same stuff. In my case I can't use a constant source term, therefore I'm dependent on fvOptions coded source.

As you said, to remove mass one has to add a source term in pEqn, because continuity equations is included in there...

I have seen stable running and validated code using specific mass flow (kg/m3/s) as source term on RHS of pEqn (pEqn was similar to the one used in rhoReactingFoam), but this was not implemented with fvOptions...

My problem is that coded source seems not to know the field p (in contrary to rho, Yi-name, h). Looking in the sourcecode of rhoReactingFoam fvOptions is called like that:

fvOptions(psi, p_rgh, rho.name())

in pEqn.H compared to that:

fvOptions(rho, Yi)

in YIEqn.H, might this be the diffrence causing trouble? Anyways would appreciate any help

carlbirger · November 28, 2019, 14:32

Hi,

I have exactly the same problem as timbojones. I want to add a mass source to simpleFoam using fvOptions. Did anybody succeed in doing this? I understand that there is a bit of programming involved to enable a source term to the P equation.

Alternatively, what is the simplest way of simulating a nozzle injection with a source term?

I would think that a mass source is one of the most basic things you woud want to include in a simulation, so this should be a question of general interest.

Any help or suggestion would be appreciated.

Carl Birger

PS. There is also this thread:

Add a mass source/sink to simpleFoam

But they point at a solution for fireFoam which from what I understand is a density based solver, for which the problem is much simpler.

December 15, 2017, 00:05	Mass source for simpleFoam-style solvers	#1
timbojones New Member Join Date: Jun 2011 Posts: 22 Rep Power: 14	Hello everyone, I've implemented a mass source term and an associated momentum source term in simpleFoam to simulate a nozzle injection that I don't want to resolve on the grid. The mass source is implemented as a source in pEqn and the momentum source in UEqn. The sources are set via custom fields and explicit source terms in these equations. I'd like to accomplish the same task using fvOptions. For the momentum source, implementation is very straightforward. However, to my understanding, the mass source should show up in pEqn, but it's not a pressure source. That is it's not a semiImplicitScalarSource on field(p). My question is this. Has anyone implemented a mass source in simpleFoam using fvOptions? Alternatively, if you've done it as custom solver with source in pEqn, is there a trick to getting this to work smoothly? Any help or sharing would be greatly appreciated! TimboJones Last edited by timbojones; December 15, 2017 at 00:07. Reason: Fixed minor grammatical errors

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April 13, 2018, 04:52		#2
benjamintu New Member Benjamin Join Date: Oct 2016 Posts: 2 Rep Power: 0	hey timbo, trying more or less the same stuff. In my case I can't use a constant source term, therefore I'm dependent on fvOptions coded source. As you said, to remove mass one has to add a source term in pEqn, because continuity equations is included in there... I have seen stable running and validated code using specific mass flow (kg/m3/s) as source term on RHS of pEqn (pEqn was similar to the one used in rhoReactingFoam), but this was not implemented with fvOptions... My problem is that coded source seems not to know the field p (in contrary to rho, Yi-name, h). Looking in the sourcecode of rhoReactingFoam fvOptions is called like that: fvOptions(psi, p_rgh, rho.name()) in pEqn.H compared to that: fvOptions(rho, Yi) in YIEqn.H, might this be the diffrence causing trouble? Anyways would appreciate any help

November 28, 2019, 14:32		#3
carlbirger New Member Carl Birger Jenssen Join Date: Feb 2017 Location: Trondheim, Norway Posts: 1 Rep Power: 0	Hi, I have exactly the same problem as timbojones. I want to add a mass source to simpleFoam using fvOptions. Did anybody succeed in doing this? I understand that there is a bit of programming involved to enable a source term to the P equation. Alternatively, what is the simplest way of simulating a nozzle injection with a source term? I would think that a mass source is one of the most basic things you woud want to include in a simulation, so this should be a question of general interest. Any help or suggestion would be appreciated. Carl Birger PS. There is also this thread: Add a mass source/sink to simpleFoam But they point at a solution for fireFoam which from what I understand is a density based solver, for which the problem is much simpler.