Turbulence Modeling of Compressible Fluid Flow with Buoyancy

为了设计火灾逃生通道，对火灾时建筑物内的烟气运动进行预测是非常重要的。在低速湍流数值模拟中，常采用流体不可压缩假设。然而，在火灾的情况下，由于高温而发生强烈的密度变化。在这样的流场中，这种假设是不可能的。因此，需要发展一种新的变密度烟气运动湍流模型。第一年，利用激光多普勒测速仪(LDV)和直径12微米的热电偶，对垂直加热平板上自然对流的湍流统计特性进行了精确测量。并对相同的流场进行了数值模拟，并与实验结果进行了比较。该模型考虑了密度涨落的影响，与实验结果吻合较好。最后一年，利用第一年发展的测量方法进行了火灾房间的模型试验。并对相同的流场进行了数值模拟，验证了第一年建立的湍流模型的准确性。

In order to design fire escapes, it is very important to predict smoke movement in a building on fire. In numerical simulation of low-speed turbulent flows, the assumption of incompressibility of fluid is usually used. However, in the case of fire, strong density variation due to high temperature occurs. In such a flowfield, that assumption cannot be made. Thus, a new turbulence model for smoke movement with variable density need to be developed. In the first year, precise measurement of turbulence statistics of natural air convection along a heated vertical plate was conducted using a Laser Doppler Velocimeter (LDV) and a fine thermocouple 12 mu m in diameter. And the same flowfield is numerically simulated and the results are compared with the above experiment. A good agreement with the experiment was found in the model which includes some effect of density fluctuation. In the last year, model experiment of a fire room was conducted by means of the measuring method developed in the first year. And same flowfield is numerically simulated and the accuracy of the turbulence model developed in the first year was confirmed.