Input Parameters
Description of the sedFoam input parameters.
The input parameters for sedFoam are numerous and are modifiable through different files in the current working directory. Some of the files are identical to other openFoam solvers and won't be described in details herein. This is the case for the files:
system/blockMesh system/controlDict system/fvSchemes system/fvSolution
The file 'blockMesh' contains the description of the mesh (see Mesh generation). The file 'controlDict' contains the runtime parameters such as the timestep and the output interval, etc... The files 'fvScheme' describes the numerical shemes for the different differential operators (temporal, divergence, laplacian) and the file 'fvSolution' describes the algebraic solvers and the associated tolerance for each equation as well as the PIMPLE algorithm controls such as the number of inner and outer iterations ...
The keyword 'faceMomentum' in the PIMPLE dictionary of the file system/fvSolution corresponds to solving the explicit shear stress terms at the cell faces and added in pEqn when set to false (the solver is using the code given in the pUf folder) and they are the cell centers and added in UEqn using the keyword 'faceMomentum' = true (the solver is using the code given in the pU folder) which is the default value.
The files that contain the specific input parameters for sedFoam are:
constant/g constant/transportProperties constant/interfacialProperties constant/forceProperties constant/ppProperties constant/granularRheologyProperties constant/kineticTheoryProperties constant/turbulenceProperties.phasea constant/turbulenceProperties.phaseb constant/twophaseRASProperties
The file 'g' contains the gravity vector. The user shall be careful when using a 1D/2D configuration that 'g' has to be carried by the 'y' direction.
Physical processes
sedFoam includes a variety of physical processes: fluid-particle forces such as drag force, fluid and particle phase rheology, elastic pressure for the solid phase, turbulence modeling. Each process can be switched on or off. The various tutorials available with the source code give a good overview of different combination of physical processes. The table below lists the keywords used to switch on or off physical processes in sedFoam and the key input parameters.
In the following the input parameters will be described file-by-file.
File transportProperties
In the file 'transportProperties' the user can specify the input parameters listed in the table below:
| parameter | description | default | range | units |
|---|---|---|---|---|
| phasea | solid phase | |||
| phased | fluid phase | |||
| rho | phase density | 1000 | 1-2650 | kg/m^3 |
| nu | phase viscosity | 1e-6 | 0-1e0 | m^2/s |
| d | particle diameter | 200e-6 | 62e-6-1 | m |
| sF | shape factor | 1 | 0.1-2 | - |
| hExp | Hindrance exponent | 2.65 | 1.5-3.15 | - |
| Ws0 | settling velocity | 1.15e-4 | 1e-6-1e-4 | m/s |
| WsGel | set. vel. gel point | 8.53e-6 | 1e-5-1e-3 | m/s |
| dimFrac | fractal dimension | 2.748 | 2-3 | - |
| Xi | empirical coef. | 1.155 | 1-10 | - |
| alphaGel | gel point | 0.28 | 0.05-0.4 | - |
| phiMax | floc concentration | 0.85 | 0.5-0.9 | - |
| rhoFloc | floc density | 1566.59 | 1050-2000 | kg/m^3 |
| alphaSmall | Min. solid vol. frac. | 1e-6 | 1e-9-1e-5 | - |
| alphaDiffusion | articifical Diffusivity | 0 | 0-1e-6 | m^2/s |
| nuMax | maximium viscosity | 1 | 1e-2-1e6 | m^2/s |
| nuFraMax | maximium sed viscosity | 1e3 | 1e-2-1e6 | m^2/s |
| nuMaxExp | idem for Explicit terms | 1 | 1e-2-1e6 | m^2/s |
File interfacialProperties
In the file 'transportProperties' the user can specified the input parameters listed in the table below:
| dragModela/b | description |
|---|---|
| Ergun | for dense packing of spheres (consistent with Darcy's law) |
| Gibilaro | |
| GidaspowErgunWenYu | |
| GidaspowSchillerNaumann | |
| SchillerNaumann | for dilute suspensions at any Re_p |
| SyamlalOBrien | |
| WenYu | |
| Camenen | for mud flocks (see Chauchat et al 2013) |
File ppProperties
In the file 'ppProperties' the user can specify the input parameters for the elastic pressure model for 'pff':
| ppModel | description |
|---|---|
| JohnsonJackson | default model (for spheres) |
| Hsu | model for spheres, Fr represents an elastic modulus |
| MerckelbachKranenburg | model for mud (based on fractal dimension) |
| Chauchat | model for mud (see Chauchat et al., 2013) |
Depending on the ppModel, the following parameters need to be specified:
| parameter | description | default | range | units |
|---|---|---|---|---|
| alphaMax | max. solid vol. fraction | 0.635 | 0.57-0.635 | - |
| alphaMinFriction | random loose packing frac. | 0.57 | 0.53-0.57 | - |
| Fr | elastic modulus | 0.05 | 0.001-1e8 | Pa |
| eta0 | empirical exponent | 3 | 1-3 | - |
| eta1 | empirical exponent | 5 | 5 | - |
File granularRheologyProperties
In the file 'granularRheologyProperties' the user can specify the input parameters for the dense granular flow rheology, in particular the user decides if he/she wants to use the dense granular flow rheology or not by setting the switch 'granularRheology' to on/off. If it's switched on, the user has to decide which rheological model to use for the different components, i.e. granular shear stress, granular normal stress and fluid shear stress, amongst:
| FrictionModel | description |
|---|---|
| none | no friction |
| Coulomb | Coulomb friction with constant friction coef mus |
| MuI | mu(I) friction model in the inertial regime |
| MuIv | mu(Iv) friction model in the viscous regime |
| PPressureModel | description |
|---|---|
| none | no particle phase shear induced pressure |
| MuI | mu(I) friction model in the inertial regime |
| MuIv | mu(Iv) friction model in the viscous regime |
| FluidViscosityModel | description |
|---|---|
| none | effective viscosity = pure fluid viscosity |
| Einstein | Einstein (1906) viscosity model for dilute supensions |
| KriegerDougherty | Krieger and Dougherty (1959) viscosity model for dense supensions |
| BoyerEtAl | Boyet et al. (2011) viscosity model for dense supensions |
The following list of parameters can be modified from the 'granularRheologyProperties' file:
| parameter | description | default | range | units |
|---|---|---|---|---|
| alphaMaxG | max. solid vol. fraction | 0.6 | 0.55-0.6 | - |
| mus | static friction coeff. | 0.38 | 0.3-0.7 | - |
| mu2 | dynamic friction coeff. | 0.64 | 0.6-1.2 | - |
| I0 | empirical coeff. mu(I) | 0.3 | 0.005-0.6 | - |
| Bphi | empirical coeff. phi(I) | 0.31 | 0.3-1 | - |
| n | exponent. effective visc. | 2.5 | 1-3 | - |
| BulkFactor | coef for 2nd viscosity | 0 | 0-10 | - |
| Dsmall | regularisation param. | 1e-6 | 1e-4-1e-9 | 1/s |
| relaxPa | relaxation factor for Pa | 1.0 | 1e-9-1 | - |
Additionally, the switch 'granularDilatancy' found in the file 'granularRheologyProperties' is used to incorporate dilatancy effects in the model. This feature is important to capture the coupling between the pore pressure feedback mechanism and the initial dynamics of a granular medium subjected to shear stress.
Finally, the 'granularCohesion' switch found in the 'granularRheologyProperties' file is used to integrate cohesive effects. This feature enables users to introduce cohesive material regions, such as cohesive layers or model fine-grained soils like clay, where cohesive effects cannot be neglected.
File kineticTheoryProperties
In the file 'kineticTheoryProperties' the user can specify the input parameters for the kinetic theory of granular flows, in particular the user decides if he/she wants to use the kinetic theory or not by setting the switch 'kineticTheory' to on/off. If it's switched on, the user has to decide which rheological model to use for the different components.
The possible closure models for the particle pressure are:
| granularPressureModel | description |
|---|---|
| Lun | |
| SyamlalRogersOBrien | |
| Torquato |
With the binary collision assumption adopted in the kinetic theory of granular flow, the radial distribution function is introduced to describe the crowdedness of a particle. Several radial distribution functions can be selected:
| radialModel | description |
|---|---|
| CarnahanStarling | |
| ChialvoSundaresan | |
| Gidaspow | |
| LunSavage | |
| SinclairJackson | |
| Torquato |
Both the particle shear viscosity and the bulk viscosity are modeled by the following closure models:
| viscosityModel | description |
|---|---|
| GarzoDufty | |
| GarzoDuftyMod | |
| Gidaspow | |
| HrenyaSinclair | |
| Syamlal | |
| none |
The conductivity of granular temperature can be computed with the following models:
| conductivityModel | description |
|---|---|
| GarzoDufty | |
| GarzoDuftyMod | |
| Gidaspow | |
| HrenyaSinclair | |
| Syamlal |
The following list of parameters can be modified from the 'kineticTheoryProperties' file:
| parameter | description | default | range | units |
|---|---|---|---|---|
| e | coeff. of restitution | 0.9 | 0.6-1.0 | - |
| muPart | interparticle friction coefficient | 0.0 | 0.0-1.0 | - |
| alphaMax | max. solid vol. fraction | 0.6 | 0.6-1.0 | - |
| MaxTheta | max.granular temperature | 1e3 | 0.001-1e5 | - |
| phi | friction angle | 32 | 20-40 | - |
| killJ2 | Tuns on (0) / off (1) the fluid-particle interaction | 1 | 0 or 1 | - |
| quadraticCorrectionJ1 | correction to consider the quadratic nature of drag | 1 | - |
File forceProperties
In the file 'forceProperties' the user can specify the input parameters for the external pressure gradient and select the fluid-particle forces to be added in the model, e.g. lift force, added mass force, Ct model:
| parameter | description | default | range | units |
|---|---|---|---|---|
| gradPMEAN | mean pressure gradient | 0 | 0- | kg/m^2/s^2 |
| gradPAMP1 | 1st order wave contribution | 0 | 0- | kg/m^2/s^2 |
| gradPAMP2 | 2nd order wave contribution | 0 | 0- | kg/m^2/s^2 |
| gradPAMP3 | 3rd order wave contribution | 0 | 0- | kg/m^2/s^2 |
| gradPAMP4 | 4th order wave contribution | 0 | 0- | kg/m^2/s^2 |
| gradPAMP5 | 5th order wave contribution | 0 | 0- | kg/m^2/s^2 |
| oscpT | wave period | 0 | 0- | s |
| initTheta1 | initial phase of 1st order wave | 0 | 0-359 | deg |
| initTheta2 | initial phase of 2nd order wave | 0 | 0-359 | deg |
| initTheta3 | initial phase of 3rd order wave | 0 | 0-359 | deg |
| initTheta4 | initial phase of 4th order wave | 0 | 0-359 | deg |
| initTheta5 | initial phase of 5th order wave | 0 | 0-359 | deg |
| tilt | to mimic bedslope with gradPMEAN | 0 | 0 or 1 | - |
| Cvm | virtual mass force coef. | 0 | 0-10 | - |
| Cl | Lift force coef. | 0 | 0-10 | - |
| Ct | Ct model coef. nuEffa=Ct^2 nutb | 0 | 0-1 | - |
| InitFreeze | Freeze solid phase | 0 | 0, 1 or 2 | - |
| fixbeddepth | depth below which to freeze | 0 | 0 to max(Y) | m |
| ClipUa | impose U.a=U.b for alpha<alphaSmall | 0 | 0 or 1 | - |
| writeTau | write shear stress tensors | false | true or false | boolean |
| debugInfo | show debugging information | false | true or false | boolean |
| spongeLayer | sponge layer | false | true or false | boolean |
| xSmin | min. X position for sponge layer | 0 | min(X)-max(X) | m |
| xSmax | max. X position for sponge layer | 0 | min(X)-max(X) | m |
File turbulenceProperties.phaseb
In the file 'turbulenceProperties.phaseb' the user can specify the turbulence model to be used for the fluid phase:
| simulationType | description |
|---|---|
| laminar | laminar flow - no turbulence model (nutb=0) |
| RAS | Reynolds Averaged turbulence model |
| LES | Large-Eddy Simulation turbulence model |
If simulationType=RAS is selected, the user needs to specify a turbulence model using the keyword 'RASModel' in the 'RAS' dictionary. All singlephase turbulence model can be selected and specific two-phase flow turbulence models are provided with sedFoam:
| RASModel | description |
|---|---|
| twophaseMixingLength | two-phase flow mixing length model (see chauchat et al. 2017, GMD) |
| twophasekEpsilon | two-phase flow k-epsilon model (see chauchat et al. 2017, GMD) |
| twophaseLaunderSharmaKE | two-phase flow k-epsilon model from Launder and Sharma |
| twophasekOmega | two-phase flow k-omega model (see chauchat et al. 2017, GMD) |
Coefficients of the turbulence models can be modified in the file turbulenceproperties.phaseb using the dictionaries twophasekOmegaCoeffs, twophaseMixingLengthCoeffs and twophasekEpsilonCoeffs. Values for the different turbulence models can be found in the tutorials.
If simulationType=LES is selected, the user needs to specify a turbulence model using the keyword 'LESModel' in the 'LES' dictionnary. For the moment, only the dynamic Lagragian sub-grid scale model from Meneveau et al. (1996) can be used with the keyword fluidDynamicLagrangian
File turbulenceProperties.phasea
In the file 'turbulenceProperties.phasea' the user can specify the turbulence model to be used for the solid phase:
| simulationType | description |
|---|---|
| laminar | laminar flow - no turbulence model (nutb=0) |
| LES | Large-Eddy Simulation turbulence model |
No RAS model is available for the solid phase. When fluid turbulence is modeled using a RAS model, simulationType keyword should be laminar for the solid phase.
If simulationType=LES is selected, the user needs to specify a turbulence model using the keyword 'LESModel' in the 'LES' dictionary. For the moment, only the dynamic Lagragian sub-grid scale model from Meneveau et al. (1996) can be used with the keyword solidDynamicLagrangian
File twophaseRASProperties
In the file 'twophaseRASProperties' the user can specified the input parameters for the turbulence model:
| parameter | description | default | range | units |
|---|---|---|---|---|
| SUSread | turbulent Schmidt number | 0 | 0-3 (0 for LES) | - |
| SUSlocal | switch to turn on local SUS model | false | true or false | boolean |
| Usmall | min. u* value for local SUS | 1e-6 | 1e-9-1e-4 | m/s |
| Cmu | Cmu constant for k-eps or k-omega | 0.09 | 0.09 | - |
| B | empirical parameter for turb drag | 0.25 | 0.1-1 | - |
| kSmall | min. Tp value for turb. drag | 1e-6 | 1e-9-1e-4 | m^2/s^2 |
| TpSmall | min. Tp value for turb. drag | 1e-6 | 1e-9-1e-4 | kg/m^3/s |
| nutMax | max. eddy viscosity value | - | 5e-3-1e1 | m^2/s |
| KE1 | coef. for density stratif (Uf-Us) | 0 | 0 or 1 | - |
| KE2 | coef. for turbulence modulation | 0 | 0 or 1 | - |
| KE3 | coef. for turbulence generation | 0 | 0 or 1 | - |
| KE4 | coef. for density stratif g | 0 | 0 or 1 | - |