diff --git a/docs/source_docs/refs.bib b/docs/source_docs/refs.bib
index 714645f65ebaa2027b9070312c1f69347d003838..38fade44354ef45584f2db86f4e7f179d3c2e42f 100644
--- a/docs/source_docs/refs.bib
+++ b/docs/source_docs/refs.bib
@@ -404,6 +404,16 @@ doi = {https://doi.org/10.1016/j.jcp.2022.111305},
doi = {10.1063/1.864230},
}
+@article{nijssen20,
+ author = {Tim M.J. Nijssen and Hans A.M. Kuipers and Jan {van der Stel} and Allert T. Adema and Kay A. Buist},
+ title = {Complete liquid-solid momentum coupling for unresolved CFD-DEM simulations},
+ journal = {International Journal of Multiphase Flow},
+ volume = {132},
+ pages = {103425},
+ year = {2020}
+}
+
+
@article{Nonaka2018,
author = {Andrew Nonaka and Marcus S. Day and John B. Bell},
title = {A conservative, thermodynamically consistent numerical approach for low Mach number combustion. Part I: Single-level integration},
@@ -601,3 +611,13 @@ doi = {https://doi.org/10.1016/j.jcp.2022.111305},
year={2007},
publisher={Elsevier}
}
+
+@article{zuber64,
+ author = {N. Zuber},
+ title = {On the dispersed two-phase flow in the laminar flow regime},
+ journal = {Chemical Engineering Science},
+ volume = {19},
+ number = {11},
+ pages = {897-917},
+ year = {1964}
+}
diff --git a/docs/source_docs/user_guide/inputs/model_options.rst b/docs/source_docs/user_guide/inputs/model_options.rst
index fe31bfc33d4e2e7ad9ee3c6267efafaa3edd00fb..6eaf50496e11e491c2aa7913f75b432df1f1fb36 100644
--- a/docs/source_docs/user_guide/inputs/model_options.rst
+++ b/docs/source_docs/user_guide/inputs/model_options.rst
@@ -291,7 +291,14 @@ The following inputs are defined using the ``mfix`` prefix.
Fluid-particle drag
-------------------
-The following input is defined using the ``mfix`` prefix.
+The following input is defined using the ``mfix.drag`` prefix.
+
+
+.. |VirtualMass_Eq| replace:: :math:`\mathbf{F}_p^{vm} = -C_p^{vm}\rho_f \left( \frac{D\mathbf{u}_f}{Dt} - \frac{d\mathbf{u}_p}{dt}\right)\mathcal{V}_p`
+
+.. |VM_Zuber_Eq| replace:: :math:`C_p^{vm} = \frac{1}{2}\frac{1+2\varepsilon_p}{1-\varepsilon_p}`
+
+.. |VM_Nijssen_Eq| replace:: :math:`\begin{split}C_p^{vm} =& C_0^{vm} \\ &+ \sum_{k=1}^3\left\{ \left[ a_{k,0} + a_{k,1} \ln \left( \frac{\rho_p}{\rho_f} \right) \right] \varepsilon_p^k \right\}\end{split}`
+--------------------------+-----------------------------------------------------------------------+-------------+-----------+
| | Description | Type | Default |
@@ -312,6 +319,24 @@ The following input is defined using the ``mfix`` prefix.
| | fluid-particle drag force. The force is applied to the fluid by | | |
| | multiplying the shear stress by fluid volume fraction. | | |
+--------------------------+-----------------------------------------------------------------------+-------------+-----------+
+| virtual_mass | Include virtual mass force in fluid-particle momentum transfer. | String | None |
+| | The virtual mass force is not included by default. | | |
+| | | | |
+| | |VirtualMass_Eq| | | |
+| | | | |
+| | * ``Null`` zero virtual mass coefficient, :math:`C_p^{vm}=0` | | |
+| | * ``Constant`` - user-specified constant coefficient | | |
+| | * ``Zuber`` :cite:p:`zuber64` | | |
+| | | | |
+| | |VM_Zuber_Eq| | | |
+| | | | |
+| | * ``Nijssen`` :cite:p:`nijssen20` | | |
+| | | | |
+| | |VM_Nijssen_Eq| | | |
+| | | | |
++--------------------------+-----------------------------------------------------------------------+-------------+-----------+
+| virtual_mass.constant | Constant virtual-mass coefficient. | Real | 0.5 |
++--------------------------+-----------------------------------------------------------------------+-------------+-----------+
.. note::