Numerical Modelling of the Turbulent Flow Developing Within and Over a 3-D Building Array, Part I: A High-Resolution Reynolds-Averaged Navier—Stokes Approach |
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Authors: | Fue-Sang Lien Eugene Yee |
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Institution: | (1) Department of Mechanical Engineering, University of Waterloo, Waterloo, Ontario, Canada;(2) Defence R & D Canada, Suffield, P.O. Box 4000, Medicine Hat, Alberta, T1A 8K6, Canada |
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Abstract: | A study of the neutrally-stratified flow within and over an array of three-dimensional buildings (cubes) was undertaken using
simple Reynolds-averaged Navier—Stokes (RANS) flow models. These models consist of a general solution of the ensemble-averaged,
steady-state, three-dimensional Navier—Stokes equations, where the k-ε turbulence model (k is turbulence kinetic energy and ε is viscous dissipation rate) has been used to close the system of equations. Two turbulence
closure models were tested, namely, the standard and Kato—Launder k-ε models. The latter model is a modified k-ε model designed specifically to overcome the stagnation point anomaly in flows past a bluff body where the standard k-ε model overpredicts the production of turbulence kinetic energy near the stagnation point. Results of a detailed comparison
between a wind-tunnel experiment and the RANS flow model predictions are presented. More specifically, vertical profiles of
the predicted mean streamwise velocity, mean vertical velocity, and turbulence kinetic energy at a number of streamwise locations
that extend from the impingement zone upstream of the array, through the array interior, to the exit region downstream of
the array are presented and compared to those measured in the wind-tunnel experiment. Generally, the numerical predictions
show good agreement for the mean flow velocities. The turbulence kinetic energy was underestimated by the two different closure
models. After validation, the results of the high-resolution RANS flow model predictions were used to diagnose the dispersive
stress, within and above the building array. The importance of dispersive stresses, which arise from point-to-point variations
in the mean flow field, relative to the spatially-averaged Reynolds stresses are assessed for the building array. |
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Keywords: | Dispersive stresses RANS k-ε models 3-D building array |
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