DNS of flow and heat transfer over rough walls (SFB/TRR150)

Deposition of the combustion products means that the inner walls of the cylinder as well as intake and exhaust lines of the internal combustion engines can be highly rough. The presence of the deposition can significantly alter the rates of heat and momentum transfer, and thereby influence the performance of the engine. It is known that turbulent statistics near rough walls is different from that of smooth walls. Having said that, turbulent flow over rough walls is much less understood even for basic flows, which calls for careful investigations.This project is carried out as a part of the DFG Collaborative Research Centre (SFB) 150: "Near-wall turbulent chemically reacting multiphase flows".

The goal of this project is providing turbulence statistics for flow over rough walls and understanding the effect of surface morphology on these statistics as well as integral quantities (friction factor and Nusselt number). These information can be used for the enhancement of roughness modeling approaches based on detached element method (DEM).

In-house pseudo-spectral  incompressible Navier-Stokes solver - SIMSON - is used for the DNS. Immersed Boundary Method is implemented in the code for addition of roughness to the solution domain. Rough surface geometries are generated using a novel algorithm, which enables reproducing stochastic roughness with desired statistical properties.