Numerical simulation of turbulent flow in ventilation ducts.

An efficient numerical method for solving the Reynolds-Averaged Navier-Stokes (RANS)equations with turbulence models for complex geometry and high Reynolds number flows isused to perform a highly-resolved computation of the turbulent flow in a strongly curved partof a ventilation duct.The three-dimensional incompressible RANS equations and the isotropic k-w two-equationnear-wall turbulence closure are written in generalized curvilinear coordinates in the strongconservation form. The discrete mean flow and turbulence closure equations are advanced intime using pointwise implicit four-stage Runge-Kutta scheme enhanced with local timestepping, variable coefficients implicit residual smoothing and multigrid acceleration.The turbulent flow through a strongly curved bend features pressure-induced secondarymotions and rotation effects on turbulence. The Reynolds number based on the bulk axialvelocity was 56690. The general conclusion is that the RANS equations in conjunction withthe isotropic two-equation near-wall model describes most global features of the flow, butneeds some further improvement to resolve some subtle details that are not fully captured bythe method.