Mixing Mechanism of Internal Hydraulic Jump

研究了两层流系统中内跃层的水力和湍流混合特性。实验结果表明，内跳流的特点是在跳流界面下方有一个与内跳流方向相反的再循环滚子流动。虽然它的起源类似于在明渠水力跳跃中观察到的滚轮，但再循环滚轮的尺寸和反向流量却非常大。此外，由于两层流体的混相密度差，辊子与跳流形成了大规模的循环形式。因此，它直接防止了内部跳跃夹带环境流体。尽管存在特征再循环辊，但在分析内跳时没有考虑到它。在充分考虑再循环辊性能的基础上，建立了动量原理模型。证实了该模型可以合理地预测内跳的混合特性作为上游密度弗劳德数的函数，这是现有的任何分析模型都无法解释的。(2)径向内跳变对径向内跳变在逐渐扩大的通道内的流动特性进行了理论和实验研究。逐渐扩大的河道是河口几何形状的一个例子。将动量原理推广到跳跃的扩展段，假设跳跃轮廓为抛物线形。将理论结果与实验结果进行了比较。(3)平面浮力面射流的代数应力模型（ASM）为了准确地考虑引力场和自由面对湍流结构的阻尼作用，建立了浮力面射流的代数应力模型。测试的ASM解与平面浮力表面射流的流动发展和湍流夹带的测量结果吻合得很好。目前正在努力将ASM应用于内部液压钻机。少

(1) Recirculating Roller Observed in Internal Hydraulic JumpThe hydraulic and turbulent mixing properties of an internal hydraulic jump were investigated in a two-layered flow system. Experimental results indicated that the internal jump was characterized by a recirculating roller flowed beneath the jump interface in the opposite direction to the internal jump flow. Although its origin was similar to the roller observed in an open channel hydraulic jump, the size and reverse flow rate of the recirculating roller were shown to be remarkably large. Besides, the roller made a large scale circulation form in connection with the jump flow because of the miscible density difference of two-layered fluids. Consequently, it directly prevented the internal jump from entraining ambient fluid. In spite of the existence of the characteristic recirculating roller, it had not been taken into consideration in analyzing an internal jump. A momentum principle model were presented in due consideration of … More the recirculating roller properties. This model was confirmed to predict the mixing properties of the internal jump as a function of the upstream densimetric Froude number reasonably, which had not been explained by any existing analytical model.(2) Radial Internal Hydraulic JumpThe flow properties of a radial internal jump within a gradually expanding channel are examined treoretically and experimentally. The gradually expanding channel follows an example of an estuary geometry. The momentum principle is extended to the expanding sections of jump by assuming that the jump profile is parabolic in shape. Theoretical results are compared with experimental ones.(3) Application of Algebraic Stress Model (ASM) to Plane Buoyant Surface Jet An algebraic stress model is developed to predict the behaviours of buoyant surface discharges for taking account of the damping effects of the gravitational field and the free surface on turbulence structure accurately. The ASM solution tested produces a good agreement with measurements on the flow development and turbulent entrainment of plane buoyant surface jets. Efforts to apply the ASM into an internal hydraulic jum are presently ongoing. Less