Hello everyone,
I'm trying to simulated an inclined open channel flow in 2D with the Lattice Boltzmann Method. I am using the body force approach of Gou et al. (2002). I set the boundary conditions of the channel as:
1. Inlet : Velocity boundary with Skodors (1993) approach.
2. Outlet : Outflow condition based in Junk and Yang (2008) approach.
3. Bed : bounce-back condition.
4. Top : free slip with specular reflection.
I would like to know if it is possible/correct to set a inlet velocity boundary condition together with the gravity body force term? All the literature that I have read implement the force terms as a driven force in a special direction.
Does anyone know some papers that have deal with this problem?
I am using OpenLB library to implement the code.
Best Regards,
Alejandro
PD: Gou et al. (2002) - Discrete Lattice effects on the forcing term in the lattice Boltzmann method.
Skodors (1993) - Initial and Boundary conditions for the lattice Boltzmann method.
Junk and Yang (2008) - Outflow boundary conditions for the lattice Boltzmann method.
Ayuzana Badarch thank you for your response. I want to simulate the case as in classical CFD approach, so I prefere to use a velocity inlet or a mass flow inlet. I am kind of confuse about the conversion of acceleration into velocity. How this can be done?
Reza Bahoosh thank you for the paper. I will read it and see how the implement it. However, I am interested at first place to use a wall with free slip condition for the case of the free surface.
Best,
Alejandro
"I would like to know if it is possible/correct to set a inlet velocity boundary condition together with the gravity body force term? All the literature that I have read implement the force terms as a driven force in a special direction."
I see no reason why it may be not correct. This is proper hydrodynamic problem. One think you should remember is to include forcing term in collision part of your BC's.
This is not exactly your case, but remember that You could always decompose P=P_1 + P_c where P_c is given, for example P_c=r*g*z, and solve the problem for unknown P_1 with "gravity" g. Then you just need to remember that P_1 is your new variable, and set BC's correctly if you prescribe pressure on BC.
Michał Dzikowski is right.
If you impose a velocity inlet/outlet condition and a force on top, you will observe that an additional pressure drop develops in your simulation. This pressure drop, together with the imposed body force density, will give the real pressure drop. It is uncommon to use velocity boundary conditions together with body forces, but it is definitely not unphysical or wrong.
For example, you may actually impose a body force pointing from the outlet to the inlet. As a consequence, the pressure drop that will develop will then be bigger to cancel this external force. If your body force points towards the outlet, the resulting pressure drop will be smaller.
- Badges
- Science topic