Coupling NSE and ADE (Poiseuille Flow)

[Nick]

Hello

I am currently researching the coupling of the Advection-Diffusion Equation (ADE) with the Navier-Stokes Equations (NSE) in OpenLB to simulate advection-diffusion in a flow field, specifically focusing on 2D Poiseuille flow. So far, I have successfully implemented both Poiseuille flow and advection-diffusion simulations independently.

Current Challenges
・Poiseuille Flow in Advection-Diffusion: I want to implement Poiseuille flow within the advectiondiffusion2d.cpp example.

・Velocity Field Usage: I understand that I need to use the velocity field generated by the NSE as input for the advection term in the ADE. However, I am unsure about the best way to extract the velocity field from the SuperLattice for Poiseuille flow and use it in the advection-diffusion process in OpenLB.

・Code Integration: I also want to maintain OpenLB conventions for dynamics, boundary conditions, and data handling while integrating these two implementations.

Specific Questions
1.Accessing the Velocity Field: What is the recommended way to extract the velocity field from the fluid lattice (SuperLattice) and use it in the advection-diffusion lattice in OpenLB?

2.Coupling Strategy: Are there existing examples or guidelines for effectively coupling NSE with ADE in OpenLB? Should I use a UnitConverter for both flow and concentration or have separate converters?

I have also reviewed user guides, but I am still unsure about the best approach for coupling. Any guidance or references would be greatly appreciated.

Thank you for your support!

[Adrian]

You can check out the thermal examples for a starting point, specifically the NavierStokesAdvectionDiffusionCoupling coupling operator used in e.g. examples/thermal/rayleighBenard3d.

In general, what you will want to do is implemement a coupling operator (cf. the FAQ section on how to write your own coupling in the user guide) that computes the velocity moment using the NSE lattice dynamics (commonly via CELL::computeU) and applies it to the ADE lattice (how this is done very much depends on the specific model you want to implement).

[Author]

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