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Author: Shutian Deng
Publisher:
ISBN: 9780542449482
Category : Mathematics
Languages : en
Pages :
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Book Description
In this paper, direct numerical simulation (DNS) of flow transition over a flat plate at a free stream Mach number of 0.5 and a Reynolds number of 1000 based on the free stream velocity and inflow displacement thickness has been carried out. The time-dependent Navier-Stokes equations are solved directly by a third-order TVD Runge-Kutta method from Shu (1998). A sixth order central compact scheme from Lele (1992) that facilitates high resolution of the flow field is used for spatial discretization together with a sixth order implicit compact filter. To avoid possible non-physical wave reflection from the boundaries, the non-reflecting boundary conditions Jiang et al. (1999) are specified at the far field and the outflow boundaries. The inflow is specified by laminar flow profile with imposed eigenmodes of two-dimensional and three-dimensional Tollmien-Schlichting (T-S) waves and random noise. The parallel computation is accomplished through the Message Passing Interface (MPI) together with a domain decomposition approach. Computation is carried out currently in three different grids levels: 256 x 32 x 64, 640 x 64 x 60 and 1536 x 128 x 64 in the streamwise (x), spanwise (y), and wall normal (z) directions. In this paper, by integrating all these papers, a better view and more detail investigations about the back ground of the study, more details on different grid levels and more complete conclusions are documented. The DNS results show the mean flow properties, such as the skin friction coefficients and the mean velocity profile, wall shear linear law, log law in the turbulent region, as well as the spatial evolution of disturbance modes which agree very well with the theoretic and experimental results. Some of the structures appeared in the transition region are also studied. In addition, the statistics and spectrum analysis of the turbulence region, kinetic energy revolution and Reynolds stress are also shown in this paper. The spectra analysis shows that our resolution at the 1536x128x64 is adequate. All computational results are in good agreement with other reported work.
Author: Shutian Deng
Publisher:
ISBN: 9780542449482
Category : Mathematics
Languages : en
Pages :
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Book Description
In this paper, direct numerical simulation (DNS) of flow transition over a flat plate at a free stream Mach number of 0.5 and a Reynolds number of 1000 based on the free stream velocity and inflow displacement thickness has been carried out. The time-dependent Navier-Stokes equations are solved directly by a third-order TVD Runge-Kutta method from Shu (1998). A sixth order central compact scheme from Lele (1992) that facilitates high resolution of the flow field is used for spatial discretization together with a sixth order implicit compact filter. To avoid possible non-physical wave reflection from the boundaries, the non-reflecting boundary conditions Jiang et al. (1999) are specified at the far field and the outflow boundaries. The inflow is specified by laminar flow profile with imposed eigenmodes of two-dimensional and three-dimensional Tollmien-Schlichting (T-S) waves and random noise. The parallel computation is accomplished through the Message Passing Interface (MPI) together with a domain decomposition approach. Computation is carried out currently in three different grids levels: 256 x 32 x 64, 640 x 64 x 60 and 1536 x 128 x 64 in the streamwise (x), spanwise (y), and wall normal (z) directions. In this paper, by integrating all these papers, a better view and more detail investigations about the back ground of the study, more details on different grid levels and more complete conclusions are documented. The DNS results show the mean flow properties, such as the skin friction coefficients and the mean velocity profile, wall shear linear law, log law in the turbulent region, as well as the spatial evolution of disturbance modes which agree very well with the theoretic and experimental results. Some of the structures appeared in the transition region are also studied. In addition, the statistics and spectrum analysis of the turbulence region, kinetic energy revolution and Reynolds stress are also shown in this paper. The spectra analysis shows that our resolution at the 1536x128x64 is adequate. All computational results are in good agreement with other reported work.
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722173401
Category :
Languages : en
Pages : 30
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The work in this report was conducted at NASA Ames Research Center during the period from August 1993 to January 1995 deals with the direct numerical simulation of transitional and turbulent flow at low Mach numbers using high-order-accurate finite-difference techniques. A computation of transition to turbulence of the spatially-evolving boundary layer on a heated flat plate in the presence of relatively high freestream turbulence was performed. The geometry and flow conditions were chosen to match earlier experiments. The development of the momentum and thermal boundary layers was documented. Velocity and temperature profiles, as well as distributions of skin friction, surface heat transfer rate, Reynolds shear stress, and turbulent heat flux were shown to compare well with experiment. The numerical method used here can be applied to complex geometries in a straightforward manner. Madavan, Nateri K. Ames Research Center NCC2-755...
Author: Jeremiah J. Gutierrez-Jensen
Publisher:
ISBN:
Category : Computational fluid dynamics
Languages : en
Pages : 106
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Many methods of passive flow control rely on changes to surface morphology. Roughening surfaces to induce boundary layer transition to turbulence and in turn delay separation is a powerful approach to lowering drag on bluff bodies. While the influence in broad terms of how roughness and other means of passive flow control to delay separation on bluff bodies is known, basic mechanisms are not well understood. Of particular interest for the current work is understanding the role of surface dimpling on boundary layers. A computational approach is employed and the study has two main goals. The first is to understand and advance the numerical methodology utilized for the computations. The second is to shed some light on the details of how surface dimples distort boundary layers and cause transition to turbulence. Simulations are performed of the flow over a simplified configuration: the flow of a boundary layer over a dimpled flat plate. The flow is modeled using an immersed boundary as a representation of the dimpled surface along with direct numerical simulation of the Navier-Stokes equations. The dimple geometry used is fixed and is that of a spherical depression in the flat plate with a depth-to-diameter ratio of 0.1. The dimples are arranged in staggered rows separated by spacing of the center of the bottom of the dimples by one diameter in both the spanwise and streamwise dimensions. The simulations are conducted for both two and three staggered rows of dimples. Flow variables are normalized at the inlet by the dimple depth and the Reynolds number is specified as 4000 (based on freestream velocity and inlet boundary layer thickness). First and second order statistics show the turbulent boundary layers correlate well to channel flow and flow of a zero pressure gradient flat plate boundary layers in the viscous sublayer and the buffer layer, but deviates further away from the wall. The forcing of transition to turbulence by the dimples is unlike the transition caused by a naturally transitioning flow, a small perturbation such as trip tape in experimental flows, or noise in the inlet condition for computational flows.
Author: Chaoqun Liu
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 48
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Book Description
The three dimensional development of flow transition in both subsonic and supersonic Joukowsky airfoil boundary layers are studied by direct numerical simulation (DNS). The numerical simulation is performed by a spatial approach. A full compressible Navier Stokes system in curvilinear coordinates is employed so that we can simulate the transition around general geometric configurations. The numerical results agree very well with the linear stability theory (LST) at the linear growth stage for both primary and second modes in the flat plate boundary layers. The whole process of controlled flow transition induced by blowing/suction around airfoils is simulated by directly solving the N-S system with Reynolds number around one million. Some differences are found in comparison to the incompressible counterpart, and some new phenomena for the transition around airfoils are observed which at least qualitatively agree with physics.
Author: M.Y. Hussaini
Publisher: Springer Science & Business Media
ISBN: 9401110328
Category : Science
Languages : en
Pages : 394
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Book Description
These two volumes contain the proceedings of the Workshop on Transition, Turbulence and Combustion, sponsored by the Insti tute for Computer Applications in Science and Engineering (ICASE) and the NASA Langley Research Center (LaRC), during June 7 to July 2, 1993. Volume I contains the contributions from the transi tion research, and Volume II contains the contributions from both the turbulence and combustion research. This is the third workshop in the series on the subject. The first was held in 1989, the second in 1991, and their proceedings were published by Springer-Verlag under the titles "Instability and Transition" (edited by M. Y. Hussaini and R. G. Voigt) and "Instability, Transition and Turbulence" (edited by M. Y. Hussaini, A. Kumar and C. L. Streett) respectively. The objectives of these workshops are to expose the academic community to current technologically important issues of transition, turbulence and combustion, and to acquaint the academic commu nity with the unique combination of theoretical, computational and experimental capabilities at LaRC. It is hoped these will foster con tinued interactions, and accelerate progress in elucidating the funda mental phenomena of transition, turbulence and combustion. The research areas of interest in transition covered the full range of the subject: linear and nonlinear stability, direct and large-eddy simulation and phenomenological modeling of the transition zone.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 40
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Author: Siegfried Wagner
Publisher: Springer Science & Business Media
ISBN: 3540450602
Category : Technology & Engineering
Languages : en
Pages : 334
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Book Description
The 24 papers presented at the international concluding colloquium of the German priority programme (DFG-Verbundschwerpunktprogramm) "Transition", held in April 2002 in Stuttgart. The unique and successful programme ran six years, starting April 1996, and was sponsored mainly by the Deutsche Forschungsgemeinschaft, DFG, but also by the Deutsches Zentrum für Luft-und Raumfahrt, DLR, the Physikalisch-Technische Bundesanstalt Braunschweig, PTB, and Airbus Deutschland. The papers summarise the results of the programme and cover transition mechanisms, transition prediction, transition control, natural transition and measurement techniques, transition - turbulence - separation, and visualisation issues. Three invited papers are devoted to mechanisms of turbulence production, to a general framework of stability, receptivity and control, and a forcing model for receptivity analysis. Almost every transition topic arising in subsonic and transonic flow is covered.
Author: Franz Durst
Publisher: Springer Science & Business Media
ISBN: 3642714358
Category : Science
Languages : en
Pages : 367
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Book Description
The first four symposia in the series on turbulent shear flows have been held alternately in the United States and Europe with the first and third being held at universities in eastern and western States, respectively. Continuing this pattern, the Fifth Symposium on Turbulent Shear Flows was held at Cornell University, Ithaca, New York, in August 1985. The meeting brought together more than 250 participants from around the world to present the results of new research on turbulent shear flows. It also provided a forum for lively discussions on the implications (practical or academic) of some of the papers. Nearly 100 formal papers and about 20 shorter communications in open forums were presented. In all the areas covered, the meeting helped to underline the vitality of current research into turbulent shear flows whether in experimental, theoretical or numerical studies. The present volume contains 25 of the original symposium presentations. All have been further reviewed and edited and several have been considerably extended since their first presentation. The editors believe that the selection provides papers of archival value that, at the same time, give a representative statement of current research in the four areas covered by this book: - Homogeneous and Simple Flows - Free Flows - Wall Flows - Reacting Flows Each of these sections begins with an introductory article by a distinguished worker in the field.
Author: O. Pironneau
Publisher: Cambridge University Press
ISBN: 9780521416184
Category : Mathematics
Languages : en
Pages : 536
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The workshop concentrated on the following turbulence test cases: T1 Boundary layer in an S-shaped duct; T2 Periodic array of cylinders in a channel; T3 Transition in a boundary layer under the influence of free-stream turbulence; T4 & T5: Axisymmetric confined jet flows.
Author: Ronald D. Joslin
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 56
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