DOC: DragForce: improve header file documentation

src/lagrangian/intermediate/submodels/Kinematic/ParticleForces/Drag/DistortedSphereDrag/DistortedSphereDragForce.H

@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2014-2017 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -30,16 +31,89 @@ Group
     grpLagrangianIntermediateForceSubModels
 
 Description
-    Drag model based on assumption of distorted spheres according to:
+    Particle-drag model wherein drag forces (per unit carrier-fluid velocity)
+    are dynamically computed by using \c sphereDrag model; however, are
+    corrected for particle distortion by linearly varying the drag between of
+    a sphere (i.e. \c sphereDrag) and a value of 1.54 corresponding to a disk.
 
+    \f[
+        \mathrm{F}_\mathrm{D} =
+            \frac{3}{4}
+            \frac{\mu_c\,\mathrm{C}_\mathrm{D}\,\mathrm{Re}_p}{\rho_p \, d_p^2}
+    \f]
+    with
+
+    \f[
+        \mathrm{C}_\mathrm{D} =
+            \mathrm{C}_{\mathrm{D, sphere}} \left( 1 + 2.632 y \right)
+    \f]
+
+    where
+    \vartable
+        \mathrm{F}_\mathrm{D}  | Drag force per carrier-fluid velocity [kg/s]
+        \mathrm{C}_\mathrm{D}  | Particle drag coefficient
+        \mathrm{C}_{\mathrm{D, sphere}} | Sphere drag coefficient
+        \mathrm{Re}_p          | Particle Reynolds number
+        \rho_p                 | Particle mass density
+        d_p                    | Particle diameter
+        y    | Level of distortion determined by other models internally
+    \endvartable
+
+    Constraints:
+    - Applicable to particles with a spatially homogeneous distribution.
+    - \f$ 1 \geq y \geq 0 \f$
+
+    References:
     \verbatim
-        "Effects of Drop Drag and Breakup on Fuel Sprays"
+        Standard model:
-        Liu, A.B., Mather, D., Reitz, R.D.,
+            Putnam, A. (1961).
-        SAE Paper 930072,
+            Integratable form of droplet drag coefficient.
-        SAE Transactions, Vol. 102, Section 3, Journal of Engines, 1993,
+            ARS Journal, 31(10), 1467-1468.
-        pp. 63-95
+
+        Standard model (tag:AOB):
+            Amsden, A. A., O'Rourke, P. J., & Butler, T. D. (1989).
+            KIVA-II: A computer program for chemically
+            reactive flows with sprays (No. LA-11560-MS).
+            Los Alamos National Lab.(LANL), Los Alamos, NM (United States).
+            DOI:10.2172/6228444
+
+        Expression correcting drag for particle distortion (tag:LMR):
+            Liu, A. B., Mather, D., & Reitz, R. D. (1993).
+            Modeling the effects of drop drag
+            and breakup on fuel sprays.
+            SAE Transactions, 83-95.
+            DOI:10.4271/930072
     \endverbatim
 
+Usage
+    Minimal example by using \c constant/\<CloudProperties\>:
+    \verbatim
+    subModels
+    {
+        particleForces
+        {
+            distortedSphereDrag;
+        }
+    }
+    \endverbatim
+
+    where the entries mean:
+    \table
+      Property     | Description                       | Type | Reqd | Deflt
+      type         | Type name: distortedSphereDrag    | word | yes  | -
+    \endtable
+
+Note
+  - \f$\mathrm{F}_\mathrm{D}\f$ is weighted with the particle mass
+    at the stage of a function return, so that it can later be normalised
+    with the effective mass, if necessary (e.g. when using virtual-mass forces).
+
+See also
+  - Foam::SphereDragForce
+
+SourceFiles
+    DistortedSphereDragForce.C
+
 \*---------------------------------------------------------------------------*/
 
 #ifndef DistortedSphereDragForce_H

src/lagrangian/intermediate/submodels/Kinematic/ParticleForces/Drag/ErgunWenYuDrag/ErgunWenYuDragForce.H

@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2013-2017 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -30,7 +31,112 @@ Group
     grpLagrangianIntermediateForceSubModels
 
 Description
-    Ergun-Wen-Yu drag model for solid spheres.
+    Particle-drag model wherein drag forces (per unit carrier-fluid
+    velocity) are dynamically computed based on the Gidaspow drag model
+    which is a switch-like combination of the Wen-Yu and Ergun drag models.
+
+    \f[
+        \mathrm{F}_{\mathrm{D}, Wen-Yu} =
+            \frac{3}{4}
+            \frac{(1 - \alpha_c) \, \mu_c \, \alpha_c \, \mathrm{Re}_p }{d_p^2}
+            \mathrm{C}_\mathrm{D} \, \alpha_c^{-2.65}
+    \f]
+
+    \f[
+        \mathrm{F}_{\mathrm{D}, Ergun} =
+            \left(150 \frac{1-\alpha_c}{\alpha_c} + 1.75 \mathrm{Re}_p \right)
+            \frac{(1-\alpha_c) \, \mu_c}{d_p^2}
+    \f]
+
+    \f[
+        \mathrm{F}_\mathrm{D} = \mathrm{F}_{\mathrm{D}, Wen-Yu}
+            \quad \mathrm{if} \quad \alpha_c \geq 0.8
+    \f]
+
+    \f[
+        \mathrm{F}_\mathrm{D} = \mathrm{F}_{\mathrm{D}, Ergun}
+            \quad \mathrm{if} \quad \alpha_c < 0.8
+    \f]
+    with
+
+    \f[
+        \mathrm{Re}_p =
+            \frac{\rho_c \, | \mathbf{u}_\mathrm{rel} | \, d_p}{\mu_c}
+    \f]
+
+    where
+    \vartable
+        \mathrm{F}_\mathrm{D} | Drag force per carrier-fluid velocity [kg/s]
+        \mathrm{C}_\mathrm{D} | Particle drag coefficient
+        \mathrm{Re}_p         | Particle Reynolds number
+        \mu_c    | Dynamic viscosity of carrier at the cell occupying particle
+        d_p                   | Particle diameter
+        \rho_c   | Density of carrier at the cell occupying particle
+        \mathbf{u}_\mathrm{rel} | Relative velocity between particle and carrier
+        \alpha_c              | Volume fraction of carrier fluid
+    \endvartable
+
+    References:
+    \verbatim
+        Standard model (tag:G):
+            Gidaspow, D. (1994).
+            Multiphase flow and fluidization:
+            continuum and kinetic theory descriptions.
+            Academic press.
+
+        Drag-coefficient model:
+            Schiller, L., & Naumann, A. (1935).
+            Über die grundlegenden Berechnungen bei der Schwerkraftaufbereitung.
+            Z. Ver. Dtsch. Ing., 77: 318–326.
+
+        Expressions (tags:ZZB, GLSLR), (Eq.16-18, Table 3):
+            Zhou, L., Zhang, L., Bai, L., Shi, W.,
+            Li, W., Wang, C., & Agarwal, R. (2017).
+            Experimental study and transient CFD/DEM simulation in
+            a fluidized bed based on different drag models.
+            RSC advances, 7(21), 12764-12774.
+            DOI:10.1039/C6RA28615A
+
+            Gao, X., Li, T., Sarkar, A., Lu, L., & Rogers, W. A. (2018).
+            Development and validation of an enhanced filtered drag model
+            for simulating gas-solid fluidization of Geldart A particles
+            in all flow regimes.
+            Chemical Engineering Science, 184, 33-51.
+            DOI:10.1016/j.ces.2018.03.038
+    \endverbatim
+
+Usage
+    Minimal example by using \c constant/\<CloudProperties\>:
+    \verbatim
+    subModels
+    {
+        particleForces
+        {
+            ErgunWenYuDrag
+            {
+                alphac    <alphacName>; // e.g. alpha.air
+            }
+        }
+    }
+    \endverbatim
+
+    where the entries mean:
+    \table
+      Property     | Description                       | Type | Reqd | Deflt
+      type         | Type name: ErgunWenYuDrag         | word | yes  | -
+      alphac       | Name of carrier fluid             | word | yes  | -
+    \endtable
+
+Note
+  - \f$\mathrm{F}_\mathrm{D}\f$ is weighted with the particle mass/density
+    at the stage of a function return, so that it can later be normalised
+    with the effective mass, if necessary (e.g. when using virtual-mass forces).
+
+See also
+  - Foam::WenYuDragForce
+
+SourceFiles
+    ErgunWenYuDragForce.C
 
 \*---------------------------------------------------------------------------*/
 

src/lagrangian/intermediate/submodels/Kinematic/ParticleForces/Drag/NonSphereDrag/NonSphereDragForce.H

@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -30,35 +31,114 @@ Group
     grpLagrangianIntermediateForceSubModels
 
 Description
-    Drag model for non-spherical particles.
+    Particle-drag model wherein drag forces (per unit carrier-fluid
+    velocity) are dynamically computed based on empirical expressions using
+    a four-parameter general drag correlation for non-spherical particles.
 
-    Takes the form of
+    \f[
+        \mathrm{F}_\mathrm{D} =
+            \frac{3}{4}
+            \frac{\mu_c\,\mathrm{C}_\mathrm{D}\,\mathrm{Re}_p}{\rho_p \, d_p^2}
+    \f]
+    with
 
-        24.0/Re*(1.0 + a_*pow(Re, b_)) + Re*c_/(Re + d_);
+    \f[
+        \mathrm{C}_\mathrm{D} =
+            \frac{24}{\mathrm{Re}_p} \left( 1 + A \, \mathrm{Re}_p^B \right)
+          + \frac{C \, \mathrm{Re}_p}{D + \mathrm{Re}_p}
+    \f]
+    where
 
-    Where a(phi), b(phi), c(phi) and d(phi) are model coefficients, with phi
+    \f[
-    defined as:
+        A = \exp(2.3288 - 6.4581\phi + 2.4486 \phi^2)
+    \f]
 
-              area of sphere with same volume as particle
+    \f[
-        phi = -------------------------------------------
+        B = 0.0964 + 0.5565\phi
-                       actual particle area
+    \f]
 
-    Equation used is Eqn (11) of reference below - good to within 2 to 4 % of
+    \f[
-    RMS values from experiment.
+        C = \exp(4.9050 - 13.8944\phi + 18.4222\phi^2 - 10.2599 \phi^3)
+    \f]
 
-    H and L also give a simplified model with greater error compared to
+    \f[
-    results from experiment - Eqn 12 - but since phi is presumed
+        D = \exp(1.4681 + 12.2584\phi - 20.7322\phi^2 + 15.8855\phi^3)
-    constant, it offers little benefit.
+    \f]
 
-    Reference:
+    \f[
+        \phi = \frac{A_p}{A_a}
+    \f]
+
+    \f[
+        \mathrm{Re}_p =
+            \frac{\rho_c \, | \mathbf{u}_\mathrm{rel} | \, d_p}{\mu_c}
+    \f]
+
+    where
+    \vartable
+        \mathrm{F}_\mathrm{D} | Drag force per carrier-fluid velocity [kg/s]
+        \mathrm{C}_\mathrm{D} | Particle drag coefficient
+        \mathrm{Re}_p         | Particle Reynolds number
+        \rho_p                | Particle mass density
+        \mu_c    | Dynamic viscosity of carrier at the cell occupying particle
+        d_p                   | Particle diameter
+        \rho_c   | Density of carrier at the cell occupying particle
+        \mathbf{u}_\mathrm{rel} | Relative velocity between particle and carrier
+        A_p        | Surface area of sphere with the same volume as the particle
+        A_a           | Actual surface area of the particle
+        \phi          | Ratio of surface areas
+    \endvartable
+
+    Constraints:
+    - Applicable to particles with a spatially homogeneous distribution.
+    - \f$ 1 \geq \phi > 0 \f$
+
+    References:
     \verbatim
-        "Drag coefficient and terminal velocity of spherical and nonspherical
+        Standard model (tag:HL), (Eq. 4,10-11):
-        particles"
+            Haider, A., & Levenspiel, O. (1989).
-        A. Haider and O. Levenspiel,
+            Drag coefficient and terminal velocity of
-        Powder Technology
+            spherical and nonspherical particles.
-        Volume 58, Issue 1, May 1989, Pages 63-70
+            Powder technology, 58(1), 63-70.
+            DOI:10.1016/0032-5910(89)80008-7
     \endverbatim
 
+Usage
+    Minimal example by using \c constant/\<CloudProperties\>:
+    \verbatim
+    subModels
+    {
+        particleForces
+        {
+            nonSphereDrag
+            {
+                phi    <phi>;
+            }
+        }
+    }
+    \endverbatim
+
+    where the entries mean:
+    \table
+      Property  | Description                       | Type | Reqd | Deflt
+      type      | Type name: nonSphereDrag          | word | yes  | -
+      phi       | Ratio of surface area of sphere having same     <!--
+                --> volume as particle to actual surface area of  <!--
+                --> particle                      | scalar | yes  | -
+    \endtable
+
+Note
+  - The drag coefficient model in (HL:Eq. 11) is good to within
+    2 to 4 \% of RMS values from the corresponding experiment.
+  - (HL:Eq. 12) also give a simplified model with greater error
+    compared to results from the experiment, but since \c phi is
+    presumed constant, Eq. 12 offers little benefit.
+  - \f$\mathrm{F}_\mathrm{D}\f$ is weighted with the particle mass
+    at the stage of a function return, so that it can later be normalised
+    with the effective mass, if necessary (e.g. when using virtual-mass forces).
+
+SourceFiles
+    NonSphereDragForce.C
 
 \*---------------------------------------------------------------------------*/
 

src/lagrangian/intermediate/submodels/Kinematic/ParticleForces/Drag/PlessisMasliyahDrag/PlessisMasliyahDragForce.H

@@ -31,7 +31,86 @@ Group
     grpLagrangianIntermediateForceSubModels
 
 Description
-    PlessisMasliyahDragForce drag model for solid spheres.
+    Particle-drag model wherein drag forces (per unit carrier-fluid
+    velocity) are dynamically computed based on the Du Plessis-Masliyah
+    drag model.
+
+    \f[
+        \mathrm{F}_\mathrm{D} =
+            \left(\mathrm{A}\, (1-\alpha_c) + \mathrm{B}\, \mathrm{Re}\right)
+            \frac{(1-\alpha_c)\, \mu_c}{\alpha_c^2\, d_p^2}
+    \f]
+    with
+
+    \f[
+        A = \frac{26.8\, \alpha_c^2}
+        {
+            \alpha_p^{2/3}
+            (1 - \alpha_p^{1/3})
+            (1 - \alpha_p^{2/3})
+        }
+    \f]
+
+    \f[
+        \mathrm{B} = \frac{\alpha_c^2}{\left( 1 - \alpha_p^{2/3} \right)^2}
+    \f]
+
+    \f[
+        \mathrm{Re}_p =
+            \frac{\rho_c \, | \mathbf{u}_\mathrm{rel} | \, d_p}{\mu_c}
+    \f]
+
+    where
+    \vartable
+        \mathrm{F}_\mathrm{D} | Drag force per carrier-fluid velocity [kg/s]
+        \mathrm{Re}_p         | Particle Reynolds number
+        \mu_c    | Dynamic viscosity of carrier at the cell occupying particle
+        d_p                   | Particle diameter
+        \rho_c   | Density of carrier at the cell occupying particle
+        \mathbf{u}_\mathrm{rel} | Relative velocity between particle and carrier
+        \alpha_c              | Volume fraction of carrier fluid
+        \alpha_p              | Volume fraction of particles
+    \endvartable
+
+    References:
+    \verbatim
+        Standard model (tag:P), (Eq. 34-36):
+            Du Plessis, J. P. (1994).
+            Analytical quantification of coefficients in the
+            Ergun equation for fluid friction in a packed bed.
+            Transport in porous media, 16(2), 189-207.
+            DOI:10.1007/BF00617551
+    \endverbatim
+
+Usage
+    Minimal example by using \c constant/\<CloudProperties\>:
+    \verbatim
+    subModels
+    {
+        particleForces
+        {
+            PlessisMasliyahDrag
+            {
+                alphac    <alphacName>; // e.g. alpha.air
+            }
+        }
+    }
+    \endverbatim
+
+    where the entries mean:
+    \table
+      Property  | Description                       | Type | Reqd | Deflt
+      type      | Type name: PlessisMasliyahDrag    | word | yes  | -
+      alphac    | Name of carrier fluid             | word | yes  | -
+    \endtable
+
+Note
+  - \f$\mathrm{F}_\mathrm{D}\f$ is weighted with the particle mass/density
+    at the stage of a function return, so that it can later be normalised
+    with the effective mass, if necessary (e.g. when using virtual-mass forces).
+
+SourceFiles
+    PlessisMasliyahDragForce.C
 
 \*---------------------------------------------------------------------------*/
 

src/lagrangian/intermediate/submodels/Kinematic/ParticleForces/Drag/SphereDrag/SphereDragForce.H

@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -30,7 +31,89 @@ Group
     grpLagrangianIntermediateForceSubModels
 
 Description
-    Drag model based on assumption of solid spheres
+    Particle-drag model wherein drag forces (per unit carrier-fluid
+    velocity) are dynamically computed based on empirical expressions.
+
+    \f[
+        \mathrm{F}_\mathrm{D} =
+            \frac{3}{4}
+            \frac{\mu_c\,\mathrm{C}_\mathrm{D}\,\mathrm{Re}_p}{\rho_p \, d_p^2}
+    \f]
+    with
+
+    \f[
+        \mathrm{C}_\mathrm{D} =
+            \frac{24}{\mathrm{Re}_p}
+            \left(1 + \frac{1}{6}\mathrm{Re}_p^{2/3} \right)
+            \quad \mathrm{if} \quad \mathrm{Re}_p \leq 1000
+    \f]
+    \f[
+        \mathrm{C}_\mathrm{D} =
+            0.424 \quad \mathrm{if} \quad \mathrm{Re}_p > 1000
+    \f]
+    and
+    \f[
+        \mathrm{Re}_p =
+            \frac{\rho_c \, | \mathbf{u}_\mathrm{rel} | \, d_p}{\mu_c}
+    \f]
+
+    where
+    \vartable
+        \mathrm{F}_\mathrm{D} | Drag force per carrier-fluid velocity [kg/s]
+        \mathrm{C}_\mathrm{D} | Particle drag coefficient
+        \mathrm{Re}_p         | Particle Reynolds number
+        \rho_p                | Particle mass density
+        \mu_c    | Dynamic viscosity of carrier at the cell occupying particle
+        d_p                   | Particle diameter
+        \rho_c   | Density of carrier at the cell occupying particle
+        \mathbf{u}_\mathrm{rel} | Relative velocity between particle and carrier
+    \endvartable
+
+    Constraints:
+    - Particles remain spherical throughout the force
+    computation, hence no particle distortion.
+    - Applicable to particles with a spatially homogeneous distribution.
+
+    References:
+    \verbatim
+        Standard model:
+            Putnam, A. (1961).
+            Integratable form of droplet drag coefficient.
+            ARS Journal, 31(10), 1467-1468.
+
+        Expressions (tag:AOB), (Eq. 34-35):
+            Amsden, A. A., O'Rourke, P. J., & Butler, T. D. (1989).
+            KIVA-II: A computer program for chemically
+            reactive flows with sprays (No. LA-11560-MS).
+            Los Alamos National Lab.(LANL), Los Alamos, NM (United States).
+            DOI:10.2172/6228444
+    \endverbatim
+
+Usage
+    Minimal example by using \c constant/\<CloudProperties\>:
+    \verbatim
+    subModels
+    {
+        particleForces
+        {
+            sphereDrag;
+        }
+    }
+    \endverbatim
+
+    where the entries mean:
+    \table
+      Property     | Description                       | Type | Reqd | Deflt
+      type         | Type name: sphereDrag             | word | yes  | -
+    \endtable
+
+Note
+  - \f$\mathrm{F}_\mathrm{D}\f$ is weighted with the particle mass/density
+    at the stage of a function return, so that it can later be normalised
+    with the effective mass, if necessary (e.g. when using virtual-mass forces).
+
+SourceFiles
+    SphereDragForce.C
 
 \*---------------------------------------------------------------------------*/
 

src/lagrangian/intermediate/submodels/Kinematic/ParticleForces/Drag/WenYuDrag/WenYuDragForce.H

@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2013-2017 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -30,7 +31,102 @@ Group
     grpLagrangianIntermediateForceSubModels
 
 Description
-    Wen-Yu drag model for solid spheres.
+    Particle-drag model wherein drag forces (per unit carrier-fluid
+    velocity) are dynamically computed based on the Wen-Yu drag model.
+
+    \f[
+        \mathrm{F}_\mathrm{D} =
+            \frac{3}{4}
+            \frac{(1 - \alpha_c) \, \mu_c \, \alpha_c \, \mathrm{Re}_p }{d_p^2}
+            \mathrm{C}_\mathrm{D} \, \alpha_c^{-2.65}
+    \f]
+    with
+
+    \f[
+        \mathrm{C}_\mathrm{D} =
+            \frac{24}{\alpha_c \, \mathrm{Re}_p}
+            \left(1 + \frac{1}{6}(\alpha_c \, \mathrm{Re}_p)^{2/3} \right)
+            \quad \mathrm{if} \quad \alpha_c \, \mathrm{Re}_p < 1000
+    \f]
+    \f[
+        \mathrm{C}_\mathrm{D} =
+            0.44 \quad \mathrm{if} \quad \alpha_c \, \mathrm{Re}_p \geq 1000
+    \f]
+    and
+    \f[
+        \mathrm{Re}_p =
+            \frac{\rho_c \, | \mathbf{u}_\mathrm{rel} | \, d_p}{\mu_c}
+    \f]
+
+    where
+    \vartable
+        \mathrm{F}_\mathrm{D} | Drag force per carrier-fluid velocity [kg/s]
+        \mathrm{C}_\mathrm{D} | Particle drag coefficient
+        \mathrm{Re}_p         | Particle Reynolds number
+        \mu_c    | Dynamic viscosity of carrier at the cell occupying particle
+        d_p                   | Particle diameter
+        \rho_c   | Density of carrier at the cell occupying particle
+        \mathbf{u}_\mathrm{rel} | Relative velocity between particle and carrier
+        \alpha_c              | Volume fraction of the carrier fluid
+    \endvartable
+
+    References:
+    \verbatim
+        Standard model:
+            Wen, C. Y., & Yu, Y. H., (1966).
+            Mechanics of fluidization.
+            Chem. Eng. Prog. Symp. Ser. 62, 100-111.
+
+        Drag-coefficient model:
+            Schiller, L., & Naumann, A. (1935).
+            Über die grundlegenden Berechnungen bei der Schwerkraftaufbereitung.
+            Z. Ver. Dtsch. Ing., 77: 318–326.
+
+        Expressions (tags:ZZB, GLSLR), (Eq.13-14, Table 3):
+            Zhou, L., Zhang, L., Bai, L., Shi, W.,
+            Li, W., Wang, C., & Agarwal, R. (2017).
+            Experimental study and transient CFD/DEM simulation in
+            a fluidized bed based on different drag models.
+            RSC advances, 7(21), 12764-12774.
+            DOI:10.1039/C6RA28615A
+
+            Gao, X., Li, T., Sarkar, A., Lu, L., & Rogers, W. A. (2018).
+            Development and validation of an enhanced filtered drag model
+            for simulating gas-solid fluidization of Geldart A particles
+            in all flow regimes.
+            Chemical Engineering Science, 184, 33-51.
+            DOI:10.1016/j.ces.2018.03.038
+    \endverbatim
+
+Usage
+    Minimal example by using \c constant/\<CloudProperties\>:
+    \verbatim
+    subModels
+    {
+        particleForces
+        {
+            WenYuDrag
+            {
+                alphac    <alphacName>; // e.g. alpha.air
+            }
+        }
+    }
+    \endverbatim
+
+    where the entries mean:
+    \table
+      Property     | Description                       | Type | Reqd | Deflt
+      type         | Type name: WenYuDrag              | word | yes  | -
+      alphac       | Name of carrier fluid             | word | yes  | -
+    \endtable
+
+Note
+  - \f$\mathrm{F}_\mathrm{D}\f$ is weighted with the particle mass/density
+    at the stage of a function return, so that it can later be normalised
+    with the effective mass, if necessary (e.g. when using virtual-mass forces).
+
+SourceFiles
+    WenYuDragForce.C
 
 \*---------------------------------------------------------------------------*/