Large eddy simulations of 45 degree inclined dense jets

Shuai Zhang, Baoxin Jiang, Adrian Law, Bing Zhao

Wednesday 1 july 2015

11:00 - 11:15h at Antarctica (level 0)

Themes: (T) Special session, (ST) Marine outfall system

Parallel session: 9D. Special Session: Marine Outfall System

Effluents that have a density heavier than the ambient environment are often discharged into the coastal waters using submerged outfalls, which behave as inclined dense jets. Typical examples include brine discharges from desalination plants and decooling water discharges from liquefied natural gas plants. In order to mitigate the potential environmental impact (Drami et al., 2011), it is necessary to design the outfalls in an optimal manner to achieve rapid mixing of the inclined dense jet with the ambient water. Hence, the prediction of the mixing characteristics of the inclined dense jet is essential for the environmental impact assessment. Upon discharges from the bottom, the inclined dense jet first rises due to the discharge momentum. After reaching a maximum height, it then falls and impacts onto the seabed due to the negative buoyancy. In the past, many experimental studies had been conducted on the phenomenon (Shao and Law, 2010). In addition, several Reynolds-averaged Navier-Stokes (RANS) simulations of the inclined dense jet with various turbulence closures were reported in the literature (Vafeiadou et al., 2005). The numerical simulations of the inclined dense jet are challenging as they involve the complex physical processes of turbulence-induced mixing with localized density gradients. In the present study, we simulate a 45° inclined turbulent dense jet using the Large Eddy Simulations (LES) approach which can better resolve the large coherent eddies in the turbulent inclined dense jet than the RANS models. The objective is to evaluate the performance of LES on the predictions of both the kinematic and mixing behavior of the inclined dense jet in the near field in a stagnant ambient. The simulations focus on the region between the discharge nozzle and the return point where the brine plume falls back to the discharge elevation after the rising trajectory. A detailed comparison between the numerical results and the available experimental results in the literature will also be presented.