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This content will become publicly available on May 18, 2018

Title: Comprehensive Evaluation of Fast-Response, Reynolds-Averaged Navier–Stokes, and Large-Eddy Simulation Methods Against High-Spatial-Resolution Wind-Tunnel Data in Step-Down Street Canyons

Three computational fluid dynamics (CFD) methods with different levels of flow-physics modelling are comprehensively evaluated against high-spatial-resolution wind-tunnel velocity data from step-down street canyons (i.e., a short building downwind of a tall building). The first method is a semi-empirical fast-response approach using the Quick Urban Industrial Complex (QUIC-URB) model. The second method solves the Reynolds-averaged Navier–Stokes (RANS) equations, and the third one utilizes a fully-coupled fluid-structure interaction large-eddy simulation (LES) model with a grid-turbulence inflow generator. Unlike typical point-by-point evaluation comparisons, here the entire two-dimensional wind-tunnel dataset is used to evaluate the dynamics of dominant flow topological features in the street canyon. Each CFD method is scrutinized for several geometric configurations by varying the downwind-to-upwind building-height ratio (H d/H u) and street canyon-width to building-width aspect ratio (S / W) for inflow winds perpendicular to the upwind building front face. Disparities between the numerical results and experimental data are quantified in terms of their ability to capture flow topological features for different geometric configurations. Ultimately, all three methods qualitatively predict the primary flow topological features, including a saddle point and a primary vortex. But, the secondary flow topological features, namely an in-canyon separation point and secondary vortices, are only wellmore » represented by the LES method despite its failure for taller downwind building cases. Misrepresentation of flow-regime transitions, exaggeration of the coherence of recirculation zones and wake fields, and overestimation of downwards vertical velocity into the canyon are the main defects in QUIC-URB, RANS and LES results, respectively. All three methods underestimate the updrafts and, surprisingly, QUIC-URB outperforms RANS for the streamwise velocity component, while RANS is superior to QUIC-URB for the vertical velocity component in the street canyon.« less
Authors:
 [1] ;  [1] ;  [2] ;  [1] ; ORCiD logo [3] ; ORCiD logo [3] ;  [1]
  1. Univ. of Utah, Salt Lake City, UT (United States). Dept. of Mechanical Engineering
  2. Pukyong National Univ., Busan (South Korea). Dept. of Environmental Atmospheric Sciences
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Information Systems and Modelling Group
Publication Date:
Report Number(s):
LA-UR-17-27285
Journal ID: ISSN 0006-8314
Grant/Contract Number:
AC52-06NA25396; CBET-PDM 1134580; CBET 1512740; ACI-1053575
Type:
Accepted Manuscript
Journal Name:
Boundary-Layer Meteorology
Additional Journal Information:
Journal Volume: 164; Journal Issue: 2; Journal ID: ISSN 0006-8314
Publisher:
Springer
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE; National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; Flow topology; Large-eddy simulation; Reynolds-averaged Navier–Stokes; Street-canyon flow
OSTI Identifier:
1392886