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- Title
Effects of Time-Dependent Inflow Perturbations on Turbulent Flow in a Street Canyon.
- Authors
Duan, G.; Ngan, K.
- Abstract
Urban flow and turbulence are driven by atmospheric flows with larger horizontal scales. Since building-resolving computational fluid dynamics models typically employ steady Dirichlet boundary conditions or forcing, the accuracy of numerical simulations may be limited by the neglect of perturbations. We investigate the sensitivity of flow within a unit-aspect-ratio street canyon to time-dependent perturbations near the inflow boundary. Using large-eddy simulation, time-periodic perturbations to the streamwise velocity component are incorporated via the nudging technique. Spatial averages of pointwise differences between unperturbed and perturbed velocity fields (i.e., the error kinetic energy) show a clear dependence on the perturbation period, though spatial structures are largely insensitive to the time-dependent forcing. The response of the error kinetic energy is maximized for perturbation periods comparable to the time scale of the mean canyon circulation. Frequency spectra indicate that this behaviour arises from a resonance between the inflow forcing and the mean motion around closed streamlines. The robustness of the results is confirmed using perturbations derived from measurements of roof-level wind speed.
- Subjects
TURBULENT flow; TIME-dependent perturbation theory; COMPUTATIONAL fluid dynamics; DIRICHLET forms; COMPUTER simulation; KINETIC energy
- Publication
Boundary-Layer Meteorology, 2018, Vol 167, Issue 2, p257
- ISSN
0006-8314
- Publication type
Article
- DOI
10.1007/s10546-017-0327-1