On the turbulence dynamics over geophysical-scale topography

Abstract eng:
Laboratory experiments were performed to quantify the spatial and temporal features of the turbulence over geophysical-scale topography defined by large-scale wavy walls. High-resolution and high-frame-rate particle image velocimetry in a refractive-index-matching channel was used to infer the distinctive dynamics of the flows in terms of the topography and Reynolds number. We place the attention on the cases with 2D and 3D walls, where the 2D topography is defined by a sinusoidal wave in the streamwise direction with amplitude to wavelength ratio a/λx = 0.05, while the 3D wall has an additional wave superimposed on the 2D wall in the spanwise direction with a/λy = 0.1. The flow over these walls is characterized at Reynolds numbers Re ∼ 4×103 and 4×104 , based on the bulk velocity and the channel half height. Turbulence statistics, flow decomposition via POD and LES-like and compensated spectra are used to gain insights into the topography modulation on the flow.

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