Re: [ESPResSo-users] Friction coefficient for virtual particle

[Ivan Cimrak]

Dear Nairhita,

The issue of correct setting of the friction parameter in lbfluid command is quite complex when simulating objects flowing in a fluid. My research group developed object-in-fluid framework in ESPResSo, that enables to model elastic objects (like cells with membranes) in ESPResSO. The object's surface is covered with triangular mesh of particles interconnected with bonds that define the elastic properties of the object's membrane.

In our case we need to properly calibrate the friction coefficient so that the drag exerted by fluid on individual mesh particles correspond to physical drag force of an object flowing in a fluid.

The friction coefficient depends on how dens mesh you are using.

Your case is modelling of solid objects, however when you use virtual particles, these also form a mesh (a solid mesh) through which the fluid exerts force on the solid object. I believe, that the friction coefficient will be the same as soon as the density of your virtual particles is similar to the density of our triangular mesh.

In next e-mail  I will send you a pre-print paper dealing with this issue.

With my best regards,

Ivan

On 02/06/2017 12:47, Nairhita Samanta wrote:

Hi all!

I wanted to ask if I am simulating a rigid spherical symmetric structure made of virtual particles on the surface of a real particle, how do I calculate the gamma (friction coefficient). Should I consider the radius of the central particle or the the radius of the rigid spherical structure. I am asking this because if in addition to this rigid structure I have simple particles as well, the viscosity of the systems should be same for all of them and I should  calculate gamma accordingly.

Regards,

Nairhita