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绿野渊

新虫 (小有名气)

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专业: 流体力学

[求助] 自然对流中的Boussinesq假设能否用来进行瞬态计算？

大家好，如题，我想请教一下自然对流中的Boussinesq假设能否用来进行瞬态计算？一直以来我都是用它来进行自然对流的瞬态计算的，尤其是不知道流体的密度随温度变化规律的时候。可是今天突然发现Fluent的tutorial里有这样一句话（http://cdlab2.fluid.tuwien.ac.at ... html/ug/node572.htm），如下所示。

“When you model natural convection inside a closed domain, the solution will depend on the mass inside the domain. Since this mass will not be known unless the density is known, you must model the flow in one of the following ways:

Perform a transient calculation. In this approach, the initial density will be computed from the initial pressure and temperature, so the initial mass is known. As the solution progresses over time, this mass will be properly conserved. If the temperature differences in your domain are large, you must follow this approach.

Perform a steady-state calculation using the Boussinesq model(described in Section 13.2.5). In this approach, you will specify a constant density, so the mass is properly specified. This approach is valid only if the temperature differences in the domain are small; if not, you must use the transient approach.”

看过这段话后我意识到了这个问题——是不是Boussinesq假设只能用于稳态计算？接着我又翻阅了几本传热传质的书籍，发现每本书里对于这个假设的推导都是基于稳态的边界层方程，这进一步加深了我的担忧。。。可是任何一个地方都没有明确说明Boussinesq假设不能用于瞬态计算。所以我现在相当纠结。。。求大侠解救一下，多谢啦:-)

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