Author: Robert L. Ash Publisher: ISBN: Category : Monte Carlo method Languages : en Pages : 54
Book Description
A Monte Carlo simulation of an unsteady, two-dimensional wall pressure field has been developed. The simulation has been evaluated in terms of the statistical properties measured in a variety of turbulent boundary layer experiments and the results are generally in good agreement. Since identifical pressure histories can be created using simulations, it has been possible to investigate the influence of receiver area (or 'microphone' size) on the statistical measurements of identical pressure histories. Based on these simulations, it was possible to conclude that the root mean square pressure levels increase in a quasi linear manner as the receiver size decreases. The trend is in substantial agreement with the experiments of Bull and Thomas, but the threshold of the diameter effect and the magnitude of the r.m.s. increase may be controlled by flow phenomena that are either ignored or improperly simulated. The power spectra are insensitive to receiver size in the energy containing frequency interval. Two-point correlations first show higher correlations with decreasing receiver size, then show poorer correlations as the receiver size becomes small enough to sense fine scale phenomena. The authors believe this simulation computer program can be valuable in studying the response of complex or non-linear structures to quasi-random wall pressure fields. The ability to adjust resolution and simulated flow conditions arbitrarily make it a flexible tool in the analyzing and designing fluid-structural systems.
Author: Niloufar Mahmoudnejad Publisher: ISBN: Category : Electronic dissertations Languages : en Pages : 186
Book Description
Pressure fluctuations associated with turbulent boundary layer have been a prominent issue over the past few decades. In order to simulate pressure fluctuations beneath a turbulent boundary layer, a numerical investigation was performed in the current study. Four different turbulence models were employed to calculate the pressure and velocity fluctuations. A new approach of direct numerical simulation (DNS) was developed, as well. The proposed DNS scheme was hybrid of sixth-order weighted compact scheme (WCS) and modified weighted essentially non-oscillatory (WENO) scheme, which is called modified WENO-WCS scheme (MWWS) hereafter. A variety of benchmark problems were investigated to evaluate the accuracy of the proposed numerical scheme. Several empirical/semi-empirical mean square pressure models and single-point wall-pressure spectrum models were investigated to compare mean square wall pressure values. Reynolds-averaged Navier-Stokes based on Spalart-Allmaras (RANS-SA) and Delayed detached-eddy simulation based on Spalart-Allmaras (DDES-SA) turbulence models showed agreement with the Lowson, Lilley and Hodgson, and Goody models. Shear stress transport (RANS-SST) and DDES-SST models showed agreement with the Lowson, Farabee and Casarella, Lilley and Hodgson, and Goody models. The MWWS scheme was in agreement with Lowson and Goody models. Five single-point wall-pressure spectrum models were investigated and compared with numerical results. In low frequency region, results obtained by DDES-SA model and MWWS scheme were in agreement with the Goody model, while RANS-SA, RANS-SST, and DDES-SST turbulence models showed agreement with the Robertson model. In High frequency region, all investigated numerical methods were in agreement with the Goody and Efimtsov (1) models.
Author: National Aeronautics and Space Administration (NASA) Publisher: Createspace Independent Publishing Platform ISBN: 9781722333911 Category : Languages : en Pages : 38
Book Description
Large-eddy simulations of a turbulent boundary layer with Reynolds number based on displacement thickness equal to 3500 were performed with two grid resolutions. The computations were continued for sufficient time to obtain frequency spectra with resolved frequencies that correspond to the most important structural frequencies on an aircraft fuselage. The turbulent stresses were adequately resolved with both resolutions. Detailed quantitative analysis of a variety of statistical quantities associated with the wall-pressure fluctuations revealed similar behavior for both simulations. The primary differences were associated with the lack of resolution of the high-frequency data in the coarse-grid calculation and the increased jitter (due to the lack of multiple realizations for averaging purposes) in the fine-grid calculation. A new curve fit was introduced to represent the spanwise coherence of the cross-spectral density. Singer, Bart A. Langley Research Center NAS1-20059; RTOP 505-59-50-02...
Author: Michel Stanislas Publisher: Springer ISBN: 3319203886 Category : Technology & Engineering Languages : en Pages : 430
Book Description
This is the proceedings of the ERCOFTAC Workshop on Progress in Wall Turbulence: Understanding and Modelling, that was held in Lille, France from June 18 to 20, 2014. The workshop brought together world specialists of near wall turbulence and stimulated exchanges between them around up-to-date theories, experiments, simulations and numerical models. This book contains a coherent collection of recent results on near wall turbulence including theory, new experiments, DNS and modeling with RANS, LES. The fact that both physical understanding and modeling by different approaches are addressed by the best specialists in a single workshop is original.
Author: Robert L. Ash
Author: Niloufar Mahmoudnejad
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Author: Robert L. Ash
Author: M. V. Lowson
Author: National Aeronautics and Space Administration (NASA)
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Author: John S. Serafini
Author: Michel Stanislas
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