Numerical investigation of the unsteady flow characteristics of human body thermal plume

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• 作者：Yulong Liu ; Yijia Zhao ; Zhengxian Liu ; Jisheng Luo
• 关键词：human thermal plume ; buoyancy ; numerical simulation ; modified turbulence viscosity ; natural convection
• 刊名：Building Simulation
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：9
• 期：6
• 页码：677-687
• 全文大小：5,044 KB
• 刊物类别：Engineering
• 刊物主题：Building Construction, HVAC and Refrigeration
  Engineering Thermodynamics and Transport Phenomena
  Atmospheric Protection, Air Quality Control and Air Pollution
  Environmental Computing and Modeling
  Chinese Library of Science
  
• 出版者：Tsinghua University Press, co-published with Springer-Verlag GmbH
• ISSN：1996-8744
• 卷排序：9

文摘

Human thermal plume is quite important to the study of airflow organization in the indoor environment, especially in the micro-environment research such as personalized ventilation, infectious disease transmission through air, etc. In order to investigate the unsteady fluctuation of the thermal plume around human body, a series of transient numerical simulations are conducted in this study. Numerical simulation based on 9.7 million grids and 0.02 s time step is performed to obtain the detail quantitative data of flow field. The obvious fluctuation and separation are captured in the upper flow region of human body based on the high resolution grids. The maximum time-averaged velocity of the thermal plume is found to be 0.25 m/s while the maximum fluctuate velocity is about 0.07 m/s. The further analysis of frequency spectrum shows that the thermal plume around the body is mainly dominated by the low frequency fluctuation which is lower than 1 Hz and the principal frequency is around 0.1 Hz. In order to overcome the drawback of the high computation cost for application of the engineering simulation, a new numerical simulation method combining a modified k–ε turbulence model and coarse grids is presented. This modified k–ε model can reduce the calculation error of Reynolds stress in the flow region of natural convection through redefining the turbulence viscosity coefficient segmentally and avoid a high numerical viscosity appeared due to the central difference scheme. It can reasonably predict the general fluctuation velocity and the frequency distribution during simulation process in coarse grids and show a huge potential to be applied to the engineering application.