Numerical Study of Turbulent Flow Fields Over Steep Terrain by Using Modified Delayed Detached-Eddy Simulations
Numerical Study of Turbulent Flow Fields Over Steep Terrain by Using Modified Delayed Detached-Eddy Simulations
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DOI：
10.1007/s10546-018-0389-8
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发表时间：
2018-09
影响因子：
4.3
通讯作者：
T. Ishihara;Y. Qi
中科院分区：
文献类型：
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作者：
T. Ishihara;Y. Qi
采用延迟分离涡模拟（DDES）方法，以给定的高度为控制参数，对二维陡坎和三维陡丘的湍流流场进行了数值模拟。利用验证度量对以往研究中典型湍流模型的适用性进行了评价。虽然所有湍流模型都能很好地模拟陡峭粗糙地形上的湍流流场，但k −ε模型高估了平均风速，低估了陡峭平坦地形上的湍流动能。大涡模拟捕捉到了大尺度涡，提高了平均风速，但由于表面粗糙度的不准确规格，高估了湍流动能。考虑表面粗糙度的分离涡模拟显示出进一步的改进，但仍然高估了湍流动能，因为使用的区域太薄，Elnolds平均的Navier-Stokes模型。修正后的DDES模型与一个新的控制参数是适合于预测的平均风速和湍流所示的瞬时流场通过涡核的可视化，和象限分析，以检查有组织的运动，与强大的有组织的运动中确定的尾区光滑的地形。二维光滑山脊背风侧出现明显的滚涡，而三维光滑山脊的尾流区出现马蹄涡。
Turbulent flow fields over a two-dimensional steep ridge and three-dimensional steep hill with rough and smooth surfaces are investigated by using a delayed detached-eddy simulation (DDES) with the specified height as a new control parameter. The applicability of typical turbulence models in previous studies is evaluated by using validation metrics. While all turbulence models simulate the turbulent flow fields over the steep rough terrain well, thek−εmodel overestimates the mean wind speed and underestimates the turbulent kinetic energy over steep, smooth terrain. The large-eddy simulation captures the large-scale vortices and improves the mean wind speed, but overestimates the turbulent kinetic energy due to the inaccurate specification of the surface roughness. The detached-eddy simulation considering the surface roughness shows further improvement, but still overestimates the turbulent kinetic energy, since the region using the Reynolds-averaged Navier–Stokes model is too thin. The modified DDES model with a new control parameter is suitable for the prediction of the mean wind speed and turbulence as demonstrated by the visualization of instantaneous flow fields through vortex cores, and a quadrant analysis to examine the organized motion, with strong organized motions identified in the wake region of smooth terrain. Roller vortices are significant on the lee side of the two-dimensional smooth ridge, while horseshoe vortices appear in the wake region of the three-dimensional smooth hill.