Minimum momentum flux ratio required to prevent air curtain breakthrough in case of cross-curtain pressure gradients: CFD versus analytical equation

Adelya Khayrullina (Corresponding author), Twan van Hooff, Claudio Alanis Ruiz, Bert Blocken, Gert Jan van Heijst

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

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.

Original languageEnglish
Pages (from-to)943-960
Number of pages18
JournalBuilding Simulation
Volume13
Issue number4
Early online date15 Apr 2020
DOIs
Publication statusPublished - 1 Aug 2020

Keywords

  • air curtain
  • CFD
  • plane turbulent jet
  • separation efficiency

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