管壁均匀密集加糙圆管流的新总流机械能方程及流动数值模拟

能量(机械能)方程是水力学的理论基础;能量损失(机械能损失)的计算既是水力学乃至工程流体力学的主要研究内容之一,也是工程实际中颇为关注的问题。以往水力学中的能量方程系以重力场中理想不可压缩流体的伯努利方程为基础而得到,其既不能直接反映紊动对流动的作用,能量损失也无明确的表达式。本文在我们现有研究工作基础上,通过理论分析与数值模拟,得到如下成果:(1)构建了管壁均匀密集加糙圆管流的新总流机械能方程;(2)通过数值模拟,对管壁均匀密集加糙圆管流的机械能损失及其构成进行了研究。构建的方程包含了紊动的作用;研究成果表明,均匀密集加糙圆管流总流机械能损失与雷诺数及管壁光滑度有关,且可分解为与时均流速梯度相关的损失及与紊动耗散相关的损失两部分。

A new mechanical energy equation for total flow in uniformly and densely roughed pipes and numerical simulation of the flow

The energy (the mechanical energy) equation is the theoretical basis for hydraulics; the calcula-tion of the energy (the mechanical energy) loss is one of the main research contents of hydraulics and engi-neering fluid mechanics as well as a concerned issue in engineering. The energy equation in hydraulics used to be deduced from the Bernoulli's equation for the ideal incompressible fluid in gravitational field. It fails to reflect the effect of turbulence on the flow directly, or give a specific formula of the energy loss. This paper is written on the basis of our existing research. By theoretical analysis and numerical simula-tion, the results are obtained as follows: (1) a new mechanical energy equation for total flow in uniformly and densely roughed pipes is built;(2) research on the energy loss and the constitution of the flow in uni-formly and densely roughed pipes is made through numerical simulation. The effect of turbulence is taken into account in this equation. The results of the research show that the mechanical energy loss for total flow in uniformly and densely roughed pipes varies with the Reynolds number and the roughness of the wall, and it can be divided into the loss related to the time averaged velocity gradients and the loss relat-ed to turbulence dissipation.