Direct numerical simulation of turbulent open channel flow: Streamwise turbulence intensity scaling and its relation to large-scale coherent motions

2023/10/27 by Christian Bauer, Bauer, Christian, Yoshiyuki Sakai +3
Engineering · #Fluid Dynamics and Turbulent Flows #Nuclear Engineering Thermal-Hydraulics #Fluid Dynamics and Vibration Analysis

paper · pdf · doi:10.48550/arxiv.2310.17948

Abstract

We conducted direct numerical simulations of turbulent open channel flow (OCF) and closed channel flow (CCF) of friction Reynolds numbers up to Re_τ≈ 900 in large computational domains up to L_x× L_z=12πh × 4πh to analyse the Reynolds number scaling of turbulence intensities. Unlike CCF, our data suggests that the streamwise turbulence intensity in OCF scales with the bulk velocity for Re_τ\gtrsim 400. The additional streamwise kinetic energy in OCF with respect to CCF is provided by larger and more intense very-large-scale motions in the former type of flow. Therefore, compared to CCF, larger computational domains of L_x× L_z=12πh× 4πh are required to faithfully capture very-large-scale motions in OCF -- and observe the reported scaling. OCF and CCF turbulence statistics data sets are available at https://doi.org/10.4121/88678f02-2a34-4452-8534-6361fc34d06b .

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