含沙水流深层排放入海的浮力射流模拟

Simulation of the Buoyant Jets Formed by the Deep Discharge of Sandy Water into the Sea

为准确评价污水深层排海对环境水域的影响,开展深水排海的数值模拟预测研究具有重要意义。建立考虑泥沙和盐度差引起的浮力射流影响的3维泥沙和盐度输移扩散的RNGκ-ε紊流模型,通过室内机理试验对模拟流场和盐度场进行了验证,模拟结果和试验结果符合较好;利用该模型对低盐度含沙水流排入某海域后的水力特性以及盐度和含沙量扩散对环境水体的影响进行模拟预测。结果表明:含沙的淡水水流排入海水后由于密度差而呈现出上升的浮力射流的特征,射流轴线在垂向上呈抛物线形态;浮力射流到达水面后,以该点为中心,呈蝴蝶型形状向四周扩散,污染带平面范围逐渐增大,影响范围内盐度持续减小,含沙量持续增加;污染带在开始时段扩散速度较快,随着掺入水体的影响范围加大,污染带边界向四周推移的速度逐渐放缓。

In order to evaluate the influence of the deep water discharged from the sewage on the marine environment accurately, considering the effect of the buoyant jet caused by different salinity and sediment, three-dimensional RNG κ- ε turbulence model was developed,including sediment scour equation and salinity advection equation. The mechanism experiment was carried out to verify the flow field and salinity field of the mathematical model. The results showed that the simulation results are in good agreement with the experiment data. The simulation for a specific discharge case was conducted to predict the hydraulic characteristics, the distribution of the sa- linity and suspended sediment after the sandy water discharge with low salinity was discharged into the sea at a certain depth, and the results demonstrated that the sewage discharged into the sea shows buoyant jet feature due to the difference of the density between the inflow and the sea water. The axis of the buoyant jet exhibits a parabolic form in the vertical plane. After the buoyant jet having reached the surface of the sea water, the salinity in the butterfly-shaped diffusion zone decreased gradually while the sediment concentration increased gradually. With the time went on, the impact of the sediment discharge on the sea water was more and more serious. In the beginning, the diffusion rate of the pollution zone was relatively faster, and it was gradually slowing down with time.