三维非静力E-ε闭合模式对山体流场及浓度分布的模拟

NUMERIC SIMULATION WITH 3-D E-ε CLOSURE MODEL ON AIR FLOW AND TURBULENCE OVER A SINGLE HILL

本文采用三维非静力E-ε闭合模式，在对流层边界层方程组中，加入湍能和耗散率方程描述边界层中的湍流运动。求解孤立三维山地地形上的流场、湍流场和浓度场，并分析地形对气流的影响及对污染物浓度分布的影响。同时做了不同坡度和不同风速下的孤立三维山体的流场、湍流场和浓度场比较。数值计算结果表明，地形能改变气流运动，气流过山时将出现分支现象，山后背坡有反向回流出现，并且回流区大小随着山体坡度的增大而增大。山体对气流的阻挡作用随山体高度的增加而更明显，随风速的增加而减弱。湍能及耗散率随高度衰减较快。随着山体坡度增加，山前气流的垂直速度也增加，湍流运动更强。风速大时湍流运动越显著。污染物在山前出现辐散，迎风坡是浓度高值区，山后背风坡也是相对高值区。山坡度越大，山前迎风坡污物浓度越高。

In the paper, some numerical simulations have been finished on the fields of air flow,turbulence and concentration over a single hill under different wind speeds, and different scale of hills. It can be seen from results that the hill has effects on the fields. The wind speed are getting slower aganist the hill,and a region of attenuation has been observed behind the hill. In front of the hill, the maximum of turbulent kinetic energy comes up at 100 meter height, but at the surface of hill, it comes up just at the surface. The dissipation rate of TKE has the same distribution as TKE, and the shear productive item of TKE also has the same distribution. The pollutant,from a pollution source situated 2km away from hill at upstream,has been affected deeply by the hill. A severe pollution region can be found easily at the front of the hill,and a pollution region with relative high concentration also can be observed just behind the hill.