Large-scale motion of submerged offset jets issuing from sharp-edged rectangular nozzles

Abstract

The mean flow, turbulence characteristics, and dynamics of large-scale vortices are investigated for an offset jet issuing from different nozzle expansion ratios using a four-receiver acoustic Doppler velocimeter. The jet was discharged from sharp-edged rectangular nozzles with expansion ratios of 0.24, 0.49, 0.75, and 1.00 at Reynolds number of 5.3 × 104. The decay rate of the maximum mean velocity decreased with increasing expansion ratio due to suppressed lateral entrainment of ambient fluid. The acoustic Doppler velocimeter proved capable of providing high-quality data to investigate the energy spectrum and turbulent structures embedded in the flow. Large-scale vortices dominated the recirculation region compared to the reattachment and developing regions of the jet. Increasing the expansion ratio resulted in larger order of magnitude of the vortices within the recirculation region. The turbulent structures stretched in the lateral direction in regions where smaller-sized structures existed in the streamwise direction and vice versa.

Experimental investigation of turbulent flow through shrouded hydrokinetic turbines

“…Figures 4 and 5 show the autocorrelation of Ruu at x/D = 0, 1, 1.7, and 2.3 for no-screen and screen configurations, respectively, at y/h of 0.46, 0.57 and 0.69. The plots exhibit the behavior of turbulence structures in a developing flow and how their properties change with time [21]. In Figure 4, the profiles indicate the temporal coherence and the size of turbulent structures in the streamwise and wall-normal directions.…”

Turbulent structures beneath semi-submerged simulated ice cover over smooth and rough bed in a shallow channel

“…They observed that the separated shear layer exhibited higher turbulent kinetic energy (TKE) over the rough surface and the growth of the TKE there began earlier relative to the separation point. Thus, separated flows are characterized by various vortex shedding modes (Fang et al, 2021;Nyantekyi-Kwakye, 2021;Nyantekyi-Kwakye et al, 2023). The reattachment length of the separated shear layer has shown to exhibit dependence on surface roughness.…”