Modelling roughness and acceleration effects with application to the flow in a hydraulic turbine

27th IAHR Symposium on Hydraulic Machinery and Systems

Yuan, J.^1 ; Nicolle, J.^2 ; Piomelli, U.^1 ; Giroux, A.-M.^2

Department of Mechanical and Materials Engineering, Queen's University Kingston, Canada^1

Institut de Recherche d'Hydro-Québec, Varennes, Canada^2

关键词: Acceleration effects;    Flow acceleration and decelerations;    Non-equilibrium flows;    Numerical predictions;    Reynolds-averaged navier-stokes simulations;    Roughness correlation;    Roughness surfaces;    Turbulent boundary layers;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/22/2/022016/pdf
DOI  :  10.1088/1755-1315/22/2/022016

来源: IOP

【 摘 要 】

This study reports the numerical predictions of flows over turbine blades, which include flow acceleration and deceleration. Two issues are addressed: (1) accurately predicting roughness effects, and (2) evaluating the performance of Reynolds-Averaged Navier-Stokes (RANS) simulations on moderately accelerating flows. For the present turbine surfaces, it is found that roughness correlations based on roughness surface slope better predict the roughness effects than both the correlations based on the moments of roughness height statistics and the IEC standard approach. It is shown that RANS simulations reproduce the flow evolution over rough-wall accelerating turbulent boundary layers, although, on a smooth wall, they fail to capture strong non-equilibrium flow behaviours. Finally, a hydraulic turbine simulation is performed to show the significant roughness impact on the total losses.