Large-scale turbulence structures in shallow separating flows
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Abstract
The Ph.D. thesis “Large-scale turbulence structures in shallow separating flows” by Harmen Talstra is the result of a Ph.D. research project on large-scale shallow-flow turbulence, which has been performed in the Environmental Fluid Mechanics Laboratory at Delft University of Technology. The dynamics of quasi two-dimensional turbulence structures in shallow separating flows have been studied both experimentally and numerically. The research work contained three parts: respectively laboratory experiments, three-dimensional simulations and two-dimensional simulations. A number of schematized flow cases have been investigated in a large-scale shallow laboratory flume, using the free-surface measurement technique of Particle Image Velocimetry (PIV). Subsequently, detailed three-dimensional Large Eddy Simulations (LES) have been performed on a parallel cluster, providing useful 3D data on the flow cases studied experimentally as well as on additional flow geometries. The conclusions drawn are useful for e.g. design purposes in engineering practice. Finally, the flow cases studied before have been revisited by means of 2D depth-averaged computations, testing a new approach to accurately resolve large-scale shallow-flow turbulence in a 2D schematization. The new approach has been coined Depth-Averaged Navier-Stokes with Large Eddy Stimulation (DANSLES). The thesis offers a rather complete picture of the turbulent flow cases that have been studied, both in terms of physical behavior and numerical modeling aspects.