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首页> 外文期刊>Building and Environment >Three-dimensional simulation of building thermal plumes merging in calm conditions: Turbulence model evaluation and turbulence structure analysis
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Three-dimensional simulation of building thermal plumes merging in calm conditions: Turbulence model evaluation and turbulence structure analysis

机译：平静条件下建筑热羽毛合并的三维模拟：湍流模型评价与湍流结构分析

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摘要

A 3D numerical modelling is conducted to investigate the thermal plumes merging and buoyancy-driven airflow in urban areas, in which poor natural ventilation causes both thermal comfort and air quality issue. The performances of five different turbulence models, i.e., three URANS (Unsteady Reynolds-averaged Navier-Stokes equations) models and two LES (Large-Eddy Simulation) models are evaluated by comparing the velocity field with previous water tank measurements. Validation results show that all four turbulence models can capture the bending of thermal plumes toward the centre, and LES models provide a better prediction on the vertical velocity profiles, while both URANS models show underestimation. The plume merging mechanism is analysed with the high accuracy LES results. Both pressure difference induced mean horizontal flow and shear instability induced turbulence are the main causes of plume merging. The coherent structure of plume merging is analysed by a quadrant analysis, which shows ejection and sweep events dominate the turbulence momentum exchange. A case study with complex urban geometry is conducted to show the impact of thermal plumes merging in the real highdensity urban areas. The convergence airflow at the pedestrian level is estimated to 2 m/s, which is comparable to wind-driven ventilation and beneficial to thermal comfort and air quality.
机译：进行了3D数值建模，以研究城市地区的热羽毛合并和浮力驱动的气流，其中自然通风差导致热舒适和空气质量问题。通过将先前的水箱测量的速度场比较，评估五种不同的湍流模型的五种不同湍流模型，即三个urans（不稳定的雷诺平均平均的Navier-Stokes方程）模型和两个LES（大涡模拟）模型。验证结果表明，所有四种湍流模型都可以捕获朝向中心的热羽毛的弯曲，并且LES模型对垂直速度剖面提供更好的预测，而两个urans模型则显示出低估。通过高精度LES结果分析羽流合并机制。压力差诱导的平均水平流量和剪切不稳定诱导的湍流是羽流合并的主要原因。通过象限分析分析了羽流合并的相干结构，其示出了喷射和扫描事件主导湍流动量交换。采用复杂的城市几何学进行了一个案例研究，以显示热羽毛在真正的高度城市地区融合的影响。行人水平的收敛气流估计为2米/ s，与风力驱动的通风相当，有利于热舒适和空气质量。

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