Extension of the algebraic transition model for the wall roughness effect

Petr Straka,Jaromír Příhoda,P Dančová,M Veselý

doi:10.1051/epjconf/201611402114

Abstract

The contribution deals with the simulation of the laminar/turbulent transition taking into account the effect of wall roughness. The correlation for the transition onset proposed by Straka and Přihoda [1] was modified for the effect of the wall roughness using the correlation according to Boyle and Stripf [2]. This correlation derived for the wall roughness formed by regularly distributed truncated cones was modified for flows over the distributed wall roughness. The algebraic transition model proposed by Straka and Přihoda [1] with the modified relation for the transition onset was verified by means of the incompressible flat-plate boundary-layer and the compressible flow through the turbine blade cascade with rough blades.

Highlights

Besides the pressure gradient, the laminar-turbulent transition in turbomachinery flows is mostly influenced by the free-stream turbulence and wall roughness
The contribution deals with the simulation of the laminar/turbulent transition taking into account the effect of wall roughness
The algebraic transition model proposed by Straka and PĜíhoda [1] with the modified relation for the transition onset was verified by means of the incompressible flat-plate boundary-layer and the compressible flow through the turbine blade cascade with rough blades

Summary

Introduction

The laminar-turbulent transition in turbomachinery flows is mostly influenced by the free-stream turbulence and wall roughness. Most models of the bypass transition take into account the effect of the free-stream turbulence and the pressure gradient only. The simulation of compressible flows through turbine blade cascades has to take into account many factors, especially the effect of pressure gradient, free-stream turbulence, and wall roughness. A typical example is the surface of turbine blades. An extensive review on the effect of wall roughness on flows in turbines was given e.g. by Bons [3]. Typical roughness of operational turbine blades was measured and studied by Bogard et al [4]. While the wall roughness effect on the modelling of turbulent flow is sufficiently described, the reliable relations for the laminar/turbulent transition on rough walls are very rare. Much less experimental results were accomplished for flows over walls with distributed roughness

Modelling of wall roughness effect

Mathematical model

Results

Conclusions