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对恒热流条件下的斜板自然对流边界层的稳定性进行了分析及数值模拟.研究发现在一定的倾角和Prandtl数范围内,三维波可存在两种不稳定模态,其临界频率分别接近于重力内波和二维T-S(Tol-mien-Schlichting)波的频率.更为特殊的是,在适当条件下该三维波模态可比二维T-S波更不稳定.这一看似违反Squire定理的结果是由于控制方程中的浮力项造成的.数值模拟初步验证了三维波的临界特性.由于稳定性总是同层流至湍流的转捩过程密切相关,计算结果可为高效换热翅片的设计提供理论依据.
The stability of the natural convection boundary layer under the condition of constant heat flux is analyzed and numerical simulation is conducted. It is found that there are two kinds of unstable modes in the three-dimensional wave with a certain inclination angle and Prandtl number. The critical frequencies are close to More specifically, this three-dimensional wave mode can be more unstable than two-dimensional TS waves under appropriate conditions.This appears to violate the Squire theorem Is due to the buoyancy term in the control equation.The numerical simulation proves the critical characteristic of the three-dimensional wave.Because the stability is always closely related to the transition from turbulent flow to turbulent flow in the same layer, the result of the calculation can be as follows: The design provides the theoretical basis.