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  • large-eddy simulation  (2)
  • AERODYNAMICS  (1)
  • Aerodynamics  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Flow, turbulence and combustion 65 (2000), S. 51-81 
    ISSN: 1573-1987
    Keywords: large-eddy simulation ; subgrid-scale models ; generalizedcoordinates ; non-orthogonal grids ; channel flows
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper presents the formulation of a mixed dynamic subgrid-scale model in non-Cartesian geometries suitable for the study of complex flows. Following the approach developed by Jordan [J. Comput. Phys. 148, 322 (1999)], the variables are first transformed into a contravariant form and then filtered in the computational space. A dynamic localized mixed model, previously developed within the Cartesian framework has been entirely re-formulated for non-orthogonal meshes. The model performance was evaluated by carrying out two tests. First, a plane channel flow at Reτ = 395 was simulated using both Cartesian and curvilinear grids; the results show that the model formulation is consistent and insensitive to grid distortion, and compares well with the reference data. Then, computations of the turbulent flow over a two-dimensional channel with a wavy wall were performed. Accurate first- and second-order statistics were obtained using relatively coarse grids.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of engineering mathematics 32 (1997), S. 217-236 
    ISSN: 1573-2703
    Keywords: turbulent shear layer ; large-eddy simulation ; subgrid-scale models ; acoustic analogy ; Lighthill's analogy.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract The effect of the small scales on the source term in Lighthill's acoustic analogy is investigated, with the objective of determining the accuracy of large-eddy simulations when applied to studies of flow-generated sound. The distribution of the turbulent quadrupole is predicted accurately, if models that take into account the trace of the SGS stresses are used. Its spatial distribution is also correct, indicating that the low-wave-number (or frequency) part of the sound spectrum can be predicted well by LES. Filtering, however, removes the small-scale fluctuations that contribute significantly to the higher derivatives in space and time of Lighthill's stress tensor T ij. The rms fluctuations of the filtered derivatives are substantially lower than those of the unfiltered quantities. The small scales, however, are not strongly correlated, and are not expected to contribute significantly to the far-field sound; separate modeling of the subgrid-scale density fluctuations might, however, be required in some configurations.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2019-06-28
    Description: A large-eddy simulation (LES) of transition in plane channel flow was carried out. The LES results were compared with those of a fine direct numerical simulation (DNS), and with those of a coarse DNS that uses the same mesh as the LES, but does not use a residual stress model. While at the early stages of transition, LES and coarse DNS give the same results: the presence of the residual stress model was found to be necessary to predict accurately mean velocity and Reynolds stress profiles during the late stages of transition (after the second spike stage). The evolution of single Fourier modes is also predicted more accurately by the LES than by the DNS. As small scales are generated, the dissipative character of the residual stress starts to reproduce correctly the energy cascade. As transition progresses, the flow approaches its fully developed turbulent state, the subgrid scales tend towards equilibrium, and the model becomes more accurate.
    Keywords: AERODYNAMICS
    Type: NASA-CR-187465 , ICASE-90-80 , NAS 1.26:187465 , AD-A229672
    Format: application/pdf
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  • 4
    Publication Date: 2019-07-10
    Description: The large-eddy simulation of the spatial evolution of a stationary crossflow vortex packet in a three-dimensional boundary layer was performed. Although a coarse grid was used (compared to that required by a direct numerical simulation) the essential features of the disturbance evolution, such as the spanwise disturbance spreading and the vortex rollover, were captured accurately. The eddy viscosity became significant only in the late nonlinear stages of the simulation.
    Keywords: Aerodynamics
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