In the present study, novel release mechanisms were developed for laboratory simulations of density-driven downbursts using the two-fluid model. The ability of these new designs in producing repeatable outflows was examined and the influence of minimizing the release cylinder wall effect was tested. The entire experimental setup was also modified to simulate the effect of translation on the resultant downburst wind flows. Planar laser induced fluorescence (PLIF) technique was utilized to visualize the flows and to provide quantitative scalar (density) field data. The results from this study showed a clear difference between the flow fields arising from the two release mechanisms, namely, a higher degree of mixing with ambient fluid, lower downward speed and higher radial propagation rate at the early stages of the simulated downburst lifecycle for the porous wall cylinder. The outflows of stationary and traveling downbursts were compared and the differences between their flow fields and propagation rates were elaborated; for the shear flows tested, a linear relationship between the downburst displacement and storm translation velocity was obtained. The radial outflows of the simulated downbursts were compared to the empirical gravity currents and the mixing of downburst and ambient fluids was quantified using calibrated PLIF images.

在本研究中，开发了新型的释放机制，用于使用双流体模型对密度驱动的爆发进行实验室模拟。检查了这些新设计产生可重复流出的能力，并测试了最小化释放缸壁效应的影响。整个实验装置也进行了修改，以模拟平移对最终爆发风流的影响。平面激光诱导荧光（PLIF）技术用于可视化流动并提供定量标量（密度）场数据。这项研究的结果表明，两种释放机理产生的流场之间存在明显差异，即与环境流体的混合程度更高，在多孔壁圆筒模拟爆破生命周期的早期阶段，较低的下降速度和较高的径向传播速率。比较了固定爆破和移动爆破的流出，并详细说明了它们的流场和传播速率之间的差异。对于所测试的剪切流，获得了爆破位移与风暴平移速度之间的线性关系。将模拟突降的径向流出与经验重力流进行比较，并使用校正后的PLIF图像量化突突和环境流体的混合。得到了下突位移与风暴平移速度之间的线性关系。将模拟突降的径向流出与经验重力流进行比较，并使用校正后的PLIF图像量化突突和环境流体的混合。得到了下突位移与风暴平移速度之间的线性关系。将模拟突降的径向流出与经验重力流进行比较，并使用校正后的PLIF图像量化突突和环境流体的混合。