基于计算流体动力学的不同流量比两股射流水垫塘的消能特性研究

为研究不同流量比的两股射流入射水垫塘后的消能特性,选用非定常不可压缩流动的N-S方程和RNG k-ε紊流模型,采用VOF(Volume of Fluid)法结合溪洛渡双曲拱坝水垫塘进行了数值模拟,分析了流量比对水垫塘底板的冲击压力、临底速度、流态特征影响,并定量研究了流场内时均动能的衰减规律。研究表明,随着上游水股射流流量的减小,上游水股对底板的冲击压力在逐渐减小,由上游水股产生的动水垫作用逐渐减弱,使得下游水股对底板的冲击压力在逐渐增大;水垫塘流场呈现为具有动水垫效应的单股射流和动水垫效应微弱的单股射流两种形态。定量计算结果表明:对于上游水股射流,时均流速梯度较大,时均动能衰减较快,且随着上游水股射流流量减小,时均动能衰减速度加快,而下游水股射流的时均流能量比值和时均消能率总体小于上游水股射流消能率。

Study on energy dissipation of two-jet with varying discharge ratio on a plunge pool based on computational fluid danamics

In order to study the energy dissipation characteristic of two jet-flow with varying discharge ratio,the unsteady in compressible flowing N-S equation,RNG k-ε turbulence model and VOF(volume of fluid)method are adopted to do the numerical simulation with reference to the Xiluodu double curvature arch dam. The impact pressure on the bottom slab of the plunge pool,the velocity and the fluid state characteristic of different flow ratio are analyzed,and the mean dynamic variation regulation in the field of flow is studied quantitatively. The research shows that,with the decreasing of the upstream jet-flow, the impact pressure on the bottom slab also decreases,and the flowing water cushion exerted by the upstream flow also lowers which makes impact pressure of the downstream flow increase gradually. There are two statuses of the plunge pool:one is the flow with the effect of flowing water cushion,the other is the flow with weakened flowing water cushion. The quantitative calculation shows that for the upstream jet-flow,the mean velocity gradient is larger,and the mean dynamic attenuation is quicker With the jet-flow lessening,the mean dynamic attenuation becomes faster than before. The discharge and dissipation ratio of the downstream are totally smaller than those of the upstream. The article gives a good reference for optimization design,the protection of plunge pool and the multi-jetting flow ratio determination.