Initial dilution of a vertical round non-buoyant jet in wavy cross-flow environment

Abstract

The phenomenon of wastewater discharged into coastal waters can be simplified as a turbulent jet under the effect of waves and currents. Previous studies have been carried out to investigate the jet behaviors under the current only or the wave only environment. To obtain better understanding of the jet behaviors in a realistic situation, a series of physical experiments on the initial dilution of a vertical round jet in the wavy cross-flow environment are conducted. The diluted processes of the jet are recorded by a high-resolution camcorder and the concentration fields of the jet are measured with a peristaltic suction pumping system. When the jet is discharged into the wavy cross-flow environment, a distinctive phenomenon, namely "effluent clouds", is observed. According to the quantitative measurements, the jet width in the wavy cross-flow environment increases more significantly than that does in the cross-flow only environment, indicating that the waves impose a positive effect on the enhancement of jet initial dilution. In order to generalize the experimental findings, a comprehensive velocity scale ua and a characteristic length scale l are introduced. Through dimensional analysis, it is found that the dimensionless centerline concentration trajectories c / y l is in proportion to 1/3 power of the dimensionless downstream distance / x l , and the dimensionless centerline dilution 2 c a / ( ) S Q u l is proportional to the square of the dimensionless centerline trajectory c / y l . Several empirical equations are then derived by using the Froude number of cross-flow Fr c as a reference coefficient. This paper provides a better understanding and new estimations of the jet initial dilution under the combined effect of waves and cross-flow current.

Transport dynamics of sediment‐laden jet: A review

“…According to previous studies on pure jet streams (Figure 12), the movement and diffusion laws of jet streams under a wavy current environment are quite different from those in still water or in a constant cross‐flow environment (Chen et al, 2008, 2012; Fang et al, 2019; Otoo et al, 2019, 2022; Y. Wang et al, 2015; Xu et al, 2016, 2017, 2018, 2019, 2020), which will inevitably have a significant impact on the movement of sediment particles in the sediment‐laden jet. Therefore, to fully capture the true movement of the sediment‐laden jet under the marine dynamic environment, the interaction between sediment‐laden jet flow with wave and current needs to be tackled.…”

“…According to previous studies on pure jet streams (Figure 12), the movement and diffusion laws of jet streams under a wavy current environment are quite different from those in still water or in a constant cross-flow environment F I G U R E 12 Instantaneous images of pure water jet under different environments: (a) Wavy environment, (b) crossflow environment, and (c) wavy crossflow environment. (Chen et al, 2008(Chen et al, , 2012Fang et al, 2019;Otoo et al, 2019Otoo et al, , 2022Y. Wang et al, 2015;Xu et al, 2016Xu et al, , 2017Xu et al, , 2018Xu et al, , 2019Xu et al, , 2020, which will inevitably have a significant impact on the movement of sediment particles in the sediment-laden jet.…”

“…The two cameras should be calibrated simultaneously with a calibration plate to ensure the shooting range is consistent. Surface added light guide plate (Y. Wang et al, 2015) may solve the problem of wave surface reflection; a new PIV and PLIF acquisition system using continuous wave laser and the high‐speed camera can increase the sampling frequency and enhance the capture of the turbulent characteristics of a sediment‐laden jet.…”