POSTECH Math

Department of Mathematics, POSTECH

Infomation

Category PDE seminar
날짜 2017-06-02 시간 14:00:00 ~ 15:15:00
장소 Math Sci Bldg 404
Speaker Jung-Il Choi Host Myoungjean Bae
소속 연세대
TOPIC Modeling and Simulation of Flow over a Rough Surface

Abstract

Recently, the analysis of flow on rough walls has gained a lot of attention because of the in-terests in micro-channels or even in urban-scale wind flows. The effects of surface roughness on fluid motion is a classical topics in fluid dynamics. Changes in resistance to a flow might be a direct response to the rough wall. In particular, the roughness in laminar flows increases the resistance and induces additional pressure drops along micro-channels. However, the role of a rough wall on flow modulations is still not clear because of difficulties in characterizing the surface of rough elements on the wall in a way that includes their irregular shapes and sizes. To better understand roughness-induced hydrodynamics, either an appropriate parametrization process or modeling of the roughness elements is needed in theoretical or computational anal-ysis. When macroscale flows are dominated by scales that are much larger than the irregular (often unknown) small imperfections on the surface, it is impossible or inefficient to solve fluid motions over rough surfaces by enforcing boundary conditions on the rough boundary geome-try. To address this issue, two distinct methods have been proposed in order to mimic the effects of actual surface roughness. One is to utilize effective boundary conditions known as wall laws to replace the irregular boundary by an artificially smoothed one that accounts for the effect of homogenized irregularities on the flow. The main idea is to filter out small-scale flow motions due to real surfaces and replace the constitutive boundary condition by a homogenized boundary condition that can provide the mean impact of the rough surface. In this approach, the proper choice or parametrization of the boundary condition is still an issue because the wall laws might include surface properties such as hydrophobicity, height changes, or textured patterns of rough surfaces. In this talk, we will discuss several issues related to 1) mathematical modeling for the effect of complex surfaces in a boundary layer on flows and heat transfer, 2) efficient numerical algorithms for simulating such complex flows and heat transfer, and 3) uncertainty quantifica-tion (UQ) techniques to investigate the sensitivity of the model coefficients incorporated with the uncertainty of the surface conditions.