CFD Online Discussion Forums - How to add the transportation equation of insoluble surfactant to interFoam?

Hello everyone
I have been studying the influence of surfactant on the droplet deformation in shear flow. Thus it is necessary to calculate the surfactant concentration and surface tension at the interface. For that, I need to add the transportation equation of insoluble surfactant to interFoam. The equations are described as follow:

$\frac{\partial f}{\partial t}+\mathbf{u}\cdot \bigtriangledown f-\mathbf{n}\cdot \bigtriangledown \mathbf{u}\cdot \mathbf{n}f=D_{f}[\bigtriangledown ^{2}f-\mathbf{n}\cdot \bigtriangledown \bigtriangledown \cdot \mathbf{n}f+k(\mathbf{n\cdot \bigtriangledown f})]$

$\gamma (f)=\gamma _{0}[1+\beta ln(1-\frac{f}{f_{\oe }})]$

where f is the surfactant concentration, Df is the surfactant diffusion coefficient, k is the curvature at the interface and n is the unit interface normal vector. So any idea of how to do that ?

Thanks in advance,
Hsin