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Minimum momentum flux ratio required to prevent air curtain breakthrough in case of cross-curtain pressure gradients: CFD versus analytical equation
Building Simulation ( IF 5.5 ) Pub Date : 2020-04-15 , DOI: 10.1007/s12273-020-0633-2
Adelya Khayrullina , Twan van Hooff , Claudio Alanis Ruiz , Bert Blocken , GertJan van Heijst

This paper presents a numerical study on the required momentum flux ratio to prevent air curtain breakthrough in case of cross-curtain (i.e. cross-jet) pressure gradients. 2D steady Reynolds-averaged Navier-Stokes (RANS) CFD simulations with the RNG k-ε turbulence model are employed for jet Reynolds numbers ranging from 5,000 to 30,000. First, the computational model is validated based on particle image velocimetry (PIV) measurements. Second, the influence of several jet parameters on the separation efficiency is evaluated for a moderate cross-jet pressure difference of 10 Pa. These are the ratio of the jet discharge momentum flux to the jet cross-flow momentum flux (momentum flux ratio), the jet height-to-width ratio and the jet discharge angle. Finally, the minimum deflection modulus to prevent jet breakthrough and the corresponding momentum flux ratio by an analytical equation and by CFD are compared. The results show that, for the configuration under study: (1) jets with the smallest height-to-width ratios (β = 18) provide the highest separation efficiency; (2) inclined jets with discharge angles α0 = 5° and 10° provide slightly higher separation efficiency than straight jets (α0 = 0°) and jets with α0 = 20°; (3) the maximum modified separation efficiency is reached at lower momentum flux ratios for jets with smaller height-to-width ratios and for inclined jets; (4) the analytical and CFD values of the optimal momentum flux ratio differ with up to 31.2%. This study shows how the separation efficiency of air curtains can be improved by adjusting certain jet parameters.

中文翻译:

在跨帘压力梯度的情况下,防止气幕穿透所需的最小动量通量比:CFD与分析方程式

本文对所需的动量通量比进行了数值研究,以防止在交叉帘(即交叉射流)压力梯度的情况下气幕突破。具有RNG k - ε的2D稳定雷诺平均Navier-Stokes(RANS)CFD模拟湍流模型用于射流雷诺数从5,000到30,000。首先,基于粒子图像测速(PIV)测量对计算模型进行验证。其次,以10 Pa的适中横喷压力差评估几种喷射参数对分离效率的影响。这些是喷射排出动量通量与喷射横流动量通量之比(动量通量比),射流高宽比和射流排放角度。最后,通过解析方程和CFD比较了防止射流穿透的最小挠度模量和相应的动量通量比。结果表明,对于正在研究的配置:(1)最小的高宽比(β= 18)提供最高的分离效率;(2)与放电的角度倾斜的射流α 0 = 5°和10°提供略微更高的分离效率比直射流(α 0 = 0°)中,用射流α 0 = 20°; (3)对于较小的高宽比的射流和倾斜的射流,在较低的动量通量比下可达到最大的改进分离效率;(4)最佳动量通量比的分析值和CFD值相差高达31.2%。这项研究表明如何通过调整某些喷射参数来提高气幕的分离效率。
更新日期:2020-04-15
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