Inlet

The inlet of a flow is usually defined by a pressure gradient or an imposed velocity. The simplest case, a prescribed uniform velocity and pressure, is a local lattice-Boltzmann boundary condition and is described below. The harder case, a turbulent inlet that reproduces a realistic atmospheric boundary layer, is a topic in its own right and is covered in the Turbulent inflow chapter (the synthetic eddy method and PODFS precursor replay).

Uniform Velocity

This boundary condition forces a uniform velocity and pressure profile. Its implementation consists of setting the populations to their equilibrium, fixing the velocity and pressure values.

(1)\[ f_{\bar{i}}\left(t+\Delta t\right)=f_{i}^{\mathrm{eq}}\left(\rho,\mathbf{u}\right) \]

Use case

Uniform velocity is used to assure a constant velocity and density inlet, which increases the simulation stability and allows for the calculation of the pressure coefficient.