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Description

The turbulentDFSEMInlet is a synthesised-eddy based velocity inlet boundary condition to generate synthetic turbulence-alike time-series from a given set of turbulence statistics for LES and DES computations.

Usage

The condition requires entries in both the boundary and field files.

Boundary file 

<patchName>
{
    type            patch;
    ...
}

Field file 

<patchName>
{
    // Mandatory entries
    type            turbulentDFSEMInlet;
    delta           <scalar>;
    R               <PatchFunction1>;
    U               <PatchFunction1>;
    L               <PatchFunction1>;

        // e.g.
        // R        uniform (<Rxx> <Rxy> <Rxz> <Ryy> <Ryz> <Rzz>);
        // U        uniform (<Ux> <Uy> <Uz>);
        // L        uniform <L>;

    // Optional entries
    d               <scalar>;
    nCellPerEddy    <label>;
    kappa           <scalar>;
    Uref            <scalar>;
    Lref            <scalar>;
    scale           <scalar>;
    m               <scalar>;
    writeEddies     <bool>;

    // Inherited entries
    ...
}

where:

Property Description Type Required Default
type Type name: turbulentDFSEMInlet word yes -
delta Characteristic length scale scalar yes -
R Reynolds-stress tensor field PatchFunction1<symmTensor> yes -
U Mean velocity field PatchFunction1<vector> yes -
L Integral-length scale field PatchFunction1<scalar> yes -
d Ratio of sum of eddy volumes to eddy box volume i.e. eddy density (fill fraction) scalar no 1.0
nCellPerEddy Minimum eddy length in units of number of cells label no 5
kappa von Karman constant scalar no 0.41
Uref Normalisation factor for Reynolds-stress tensor and mean velocity scalar no 1.0
Lref Normalisation factor for integral-length scale scalar no 1.0
scale Heuristic scaling factor being applied on the normalisation factor C1 scalar no 1.0
m The power of V defined in C1 scalar no 0.5
writeEddies Flag to write eddies as OBJ file bool no false

The inherited entries are elaborated in:

  • Foam::fixedValueFvPatchField
  • Foam::PatchFunction1

  • Foam::PatchFunction1Types::MappedFile

  • The delta value typically represents the characteristic scale of flow or flow domain, e.g. a channel half height for plane channel flows.
  • nCellPerEddy and scale entries are heuristic entries which do not exist in the standard method, yet are necessary to reproduce the results published in the original journal paper.
  • In the original journal paper, C1 in Eq. 11 is not dimensionless. It is not clear whether this dimensionality issue was intentional. To alleviate this matter, users can alter the input entry m, which is the power of the eddy-box volume defined in the C1, to obtain a dimensionless C1 coefficient. The default value of m is 0.5, which is the value stated in the original journal paper, and m=1/3 leads to a dimensionless C1.

Further information

Tutorial:

Source code:

API:

History: