Large Eddy Simulation of Wind Field around Large-Span Cantilevered Roofs

Large-span cantilevered roofs are wind sensitive structures, this paper presents the finding of large eddy simulation(LES) of turbulent wind field around large-span cantilevered roofs with grandstand in atmosphere boundary layer. For a typical horizontal cantilevered roof, the wind pressure is researched in fluid mechanic view, the large scales of wind motion are computed explicitly while the small scales are modeled by LES, the contours of wind pressure and velocity are present to reveal the coherent structures. Some general issues related to LES in wind engineering are discussed also.

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Large Eddy Simulation of Coherent Structures over Forest Canopy

Notes on Numerical Fluid Mechanics and Multidisciplinary Design - Turbulence and Interactions ◽

10.1007/978-3-642-14139-3_17 ◽

2010 ◽

pp. 143-149 ◽

Cited By ~ 2

Author(s):

K. Gavrilov ◽

G. Accary ◽

D. Morvan ◽

D. Lyubimov ◽

O. Bessonov ◽

...

Keyword(s):

Large Eddy Simulation ◽

Coherent Structures ◽

Forest Canopy ◽

Eddy Simulation ◽

Large Eddy

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Large-eddy simulation of turbulent flows over an urban building array with the ABLE-LBM and comparison with 3D MRI observed data sets

Environmental Fluid Mechanics ◽

10.1007/s10652-020-09770-6 ◽

2020 ◽

Author(s):

Yansen Wang ◽

Michael J. Benson

Keyword(s):

Boundary Layer ◽

Kinetic Energy ◽

Large Eddy Simulation ◽

Atmospheric Boundary Layer ◽

Validation Study ◽

Tall Building ◽

Turbulent Wind ◽

Eddy Simulation ◽

Large Eddy ◽

Building Array

Abstract In this article we describe the details of an ABLE-LBM (Atmospheric Boundary Layer Environment-Lattice Boltzmann Model) validation study for urban building array turbulent flow simulations. The ABLE-LBM large-eddy simulation results were compared with a set of 3D magnetic resonance image (MRI) velocimetry data. The ABLE-LBM simulations used the same building layout and Reynolds numbers operated in the laboratory water channel. The building set-up was an evenly spaced orthogonal array of cubic buildings (height = H) with a central tall building (height = 3H) in the second row. Two building orientations, angled with 0°and 45° wind directions, were simulated with ABLE-LBM. The model produced horizontal and vertical fields of time-averaged velocity fields and compared well with the experimental results. The model also produced urban canyon flows and vortices at front and lee sides and over building tops that were similar in strength and location to the laboratory studies. The turbulent kinetic energy associated with these two wind directions were also presented in this simulation study. It is shown that the building array arrangement, especially the tall building, has a great effect on turbulent wind fields. There is a Karman vortex street on the lee side of the tall building. High turbulent intensity areas are associated with the vortex shedding motions at building edges. In addition, the wind direction is a very important factor for turbulent wind and kinetic energy distribution. This validation study indicated that ABLE-LBM is a viable simulation model for turbulent atmospheric boundary layer flows in the urban building array. The computational speed of ABLE-LBM using the GPU has shown that real-time LES simulation is realizable for a computational domain with several millions grid points.

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Large-Eddy Simulation of Unsteady Surface Pressure Over a LP Turbine Blade Due to Interactions of Passing Wakes and Inflexional Boundary Layer

Volume 6: Turbo Expo 2005, Parts A and B ◽

10.1115/gt2005-68867 ◽

2005 ◽

Cited By ~ 1

Author(s):

S. Sarkar ◽

Peter R. Voke

Keyword(s):

Large Eddy Simulation ◽

Turbine Blade ◽

Coherent Structures ◽

Pressure Fluctuations ◽

Time Dependent ◽

Suction Surface ◽

Eddy Simulation ◽

Large Eddy ◽

Grid Points ◽

Lp Turbine

The unsteady pressure over the suction surface of a modern low-pressure (LP) turbine blade subjected to periodically passing wakes from a moving bar wake generator is described. The results presented are a part of detailed Large-Eddy Simulation (LES) following earlier experiments over the T106 profile for a Reynolds number of 1.6×105 (based on the chord and exit velocity) and the cascade pitch to chord ratio of 0.8. The present LES uses coupled simulations of cylinder for wake, providing four-dimensional inflow conditions for successor simulations of wake interactions with the blade. The three-dimensional, time-dependent, incompressible Navier-Stokes equations in fully covariant form are solved with 2.4×106 grid points for the cascade and 3.05×106 grid points for the cylinder using a symmetry-preserving finite difference scheme of second-order spatial and temporal accuracy. A separation bubble on the suction surface of the blade was found to form under the steady state condition. Pressure fluctuations of large amplitude appear on the suction surface as the wake passes over the separation region. Enhanced receptivity of perturbations associated with the inflexional velocity profile is the cause of instability and coherent vortices appear over the rear half of the suction surface by the rollup of shear layer via Kelvin-Helmholtz (K-H) mechanism. Once these vortices are formed, the steady-flow separation changes remarkably. These coherent structures embedded in the boundary amplify before breakdown while traveling downstream with a convective speed of about 37 percent of the local free-stream speed. The vortices play an important role in the generation of turbulence and thus to decide the transitional length, which becomes time-dependent. The source of the pressure fluctuations on the rear part of the suction surface is also identified as the formation of these coherent structures. When compared with experiments, it reveals that LES is worth pursuing as an understanding of the eddy motions and interactions is of vital importance for the problem.

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