Investigation on Flow Characteristics and Entrainment for lnclined Thermals as well as the Front of lnclined Strating Plumes

本文从理论上和实验上研究了沿下坡运动的二维保守重力流，即倾斜起始羽流和倾斜热气流的混相现象。在理论研究中，建立了倾斜热气流和倾斜起始羽流的积分模型。所提出的模型包含了所涉及的主要物理原理。在广泛的实际应用中，各自的模型能够预测流厚、速度和密度等羽流或热特性，并且比任何现有模型都具有更高的精度。在实验研究中，对倾斜热气流和倾斜起始羽流进行了一系列广泛的实验室实验，以量化一些重要的流动特征，包括流动的几何形状、形状因素、空间增长率、锋面传播速度和夹带函数。从大量现有实验数据的应用中发现，在rheta=5 ~ 90范围内，这些流动特性大多是底坡角rheta的函数，因此可以量化为rheta的函数。在底坡角rheta=5 ~ 90 <s:1>范围内，除了锋面传播速度外，倾斜热气流与倾斜起始羽流锋面之间的流动特性没有显著差异。理论和实验还发现，前缘传播速度U_f、流动厚度H_f和平均浮力B_f对纵向距离x的依赖关系为：U_f=constant with x、H_f-x和B_f-x^<-1>，而倾斜起始羽流前缘的U_f-x^<-1/2>、H_f-x、B_f-x^<-2>。

Miscible conservative two-dimensional gravity currents traveling downslope, namely, inclined starting plumes and inclined thermals were investigated theoretically and experimentally.In theoretical study, integral models were formulated for inclined thermals and inclined starting plumes. The proposed models incorporate the maior physical principles involved. For a wide range of practical applications, respective model is capable of predicting such plume or thermal characteristics as flow thickness, velocity, and density with higher accuracy than any available models.In Experimental study, a series of extensive laboratory experiments for inclined thermals and inclined starting plumes were conducted to quantify a number of important flow characteristics, including the geometry, shape factors, spatial growth rates, front propagation speeds, and entrainment functions of the flows. It is found from the application of a large volume of present experimental data that these flow characteristics are at most functions of bottom slope angle rheta for the range of rheta=5-90ﾟ and, consequently, were quantified as functions of rheta. It is also found that, except front propagation speed, no significant differences are identified regarding the flow characteristics between inclined thermals and the front of inclined starting plumes for the range of bottom slope angle rheta=5-90ﾟ.It is also found theoretically and experimentally that the dependence of the front propagation speed U_f, flow thichness H_f, and mean buoyancy B_f on longitudinal distance x are U_f=constant with x, H_f-x, and B_f-x^<-1> in inclined thermals, whereas U_f-x^<-1/2>, H_f-x, B_f-x^<-2> in the front of inclined starting plumes.