Download or read book Compressibility Variable Density and Curvature Effects on Turbulent Shear Layers written by Kristen Matsuno and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent mixing layers occur between two streams of fluids with different kinematic and/or thermodynamic properties, and are fundamental flow features which influence the dynamics of a wide variety of applications, ranging from the mixing efficiency of fuel injection in internal combustion to vehicle loads in external aerodynamics. Two motivating applications behind this research include the study of high-speed jets in cross-flow and supersonic retro-propulsion, which occurs as aerospace vehicles use jet plumes to decelerate during entry, descent, and landing. Both these applications are highly influenced by hot jet plumes under highly compressible conditions which exhibit significant streamwise curvature. Simulating the entire flow field associated with such applications is extremely computationally expensive; capturing all important flow features at full resolution is exorbitant for the purposes of engineering design. Thus, grasping the full behavior of turbulent mixing layers in a representative parameter space enables the development of models which can reliably and accurately predict the complex flow fields present in these engineering applications. This work enriches the present understanding of mixing in turbulent shear layers via the systematic inclusion of compressibility, variable density, and streamwise curvature effects. The spreading, or growth rate, of turbulent shear layers is known to decrease with increasing compressibility. Dilatational velocities and pressure-dilatation magnitudes show little contribution to shear layer growth rates, even under highly compressible conditions. A new turbulent length and velocity scale is introduced and shown to scale key turbulent quantities. Inclusion of freestream density variations are also known to decreasing mixing layer growth rates. Trends with increasing compressibility and the importance of mixing layer asymmetry are identified--shear layer centerlines and turbulent stresses in variable density shear layers are biased towards the less-dense freestream, which reduces the turbulent mixing of the mean momentum profile and corresponding growth rates. The combined effects of compressibility and streamwise curvature are demonstrated to be comparable for the selected parameter space. Shear layer growth rates are dominated by the freestream density ratio when streamwise curvature is significant. Changes to model predictions of turbulent growth rates and turbulent kinetic energy levels resulting from various model modifications are evaluated. Reduced accuracy in model predictions of turbulent kinetic energy magnitudes under curved conditions, even with the inclusion of compressibility and curvature modifications, is demonstrated.

Download or read book Compressibility Effects in Turbulent Nonpremixed Reacting Shear Flows written by Carlos Pantano-Rubino and published by . This book was released on 2000 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Stabilizing Effect of Compressibility in Turbulent Shear Flow written by S. Sarkar and published by . This book was released on 1994 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Og lnopolska Konferencja Warsztat Pracy Projektanta Konstrukcji 1 written by and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Compressibility Turbulence and High Speed Flow written by Thomas B. Gatski and published by Academic Press. This book was released on 2013-03-05 with total page 343 pages. Available in PDF, EPUB and Kindle. Book excerpt: Compressibility, Turbulence and High Speed Flow introduces the reader to the field of compressible turbulence and compressible turbulent flows across a broad speed range, through a unique complimentary treatment of both the theoretical foundations and the measurement and analysis tools currently used. The book provides the reader with the necessary background and current trends in the theoretical and experimental aspects of compressible turbulent flows and compressible turbulence. Detailed derivations of the pertinent equations describing the motion of such turbulent flows is provided and an extensive discussion of the various approaches used in predicting both free shear and wall bounded flows is presented. Experimental measurement techniques common to the compressible flow regime are introduced with particular emphasis on the unique challenges presented by high speed flows. Both experimental and numerical simulation work is supplied throughout to provide the reader with an overall perspective of current trends. - An introduction to current techniques in compressible turbulent flow analysis - An approach that enables engineers to identify and solve complex compressible flow challenges - Prediction methodologies, including the Reynolds-averaged Navier Stokes (RANS) method, scale filtered methods and direct numerical simulation (DNS) - Current strategies focusing on compressible flow control

Download or read book On Turbulent Shear Flows of Variable Density written by John Laufer and published by . This book was released on 1968 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study was made of the mean flow field of free turbulent layers of variable density showing that if the velocity distribution in a particular constant-density flow is known, it is possible to obtain the corresponding variable-density velocity field without the introduction of a compressible turbulent viscosity. This is accomplished by a Dorodnitsyn-Howarth type of transformation applied to the time-dependent equations of motion rather than to the mean equations of motion, as has been done previously. When the transformed equations are averaged, using Reynolds' method, the incompressible turbulent equations for the mean flow are obtained. These equations can then be handled by conventional methods. Predictions obtained by this procedure agree well with experimental results.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 836 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Direct Simulation of Compressible Turbulence in a Shear Flow written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-02 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: Compressibility effects on the turbulence in homogeneous shear flow are investigated. The growth of the turbulent kinetic energy was found to decrease with increasing Mach number: a phenomenon which is similar to the reduction of turbulent velocity intensities observed in experiments on supersonic free shear layers. An examination of the turbulent energy budget shows that both the compressible dissipation and the pressure-dilatation contribute to the decrease in the growth of kinetic energy. The pressure-dilatation is predominantly negative in homogeneous shear flow, in contrast to its predominantly positive behavior in isotropic turbulence. The different signs of the pressure-dilatation are explained by theoretical consideration of the equations for the pressure variance and density variance. Previously, the following results were obtained for isotropic turbulence: (1) the normalized compressible dissipation is of O(M(sub t)(exp 2)); and (2) there is approximate equipartition between the kinetic and potential energies associated with the fluctuating compressible mode. Both of these results were substantiated in the case of homogeneous shear. The dilatation field is significantly more skewed and intermittent than the vorticity field. Strong compressions seem to be more likely than strong expansions. Sarkar, S. and Erlebacher, G. and Hussaini, M. Y. Unspecified Center NAS1-18605; RTOP 505-90-52-01...

Download or read book On Modelling the Effects of Streamline Curvature on Turbulent Shear Flows written by Bassam A. Younis and published by . This book was released on 1984 with total page 436 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Calculation of Turbulent Boundary Layers with Heat Transfer and Pressure Gradient Utilizing a Compressibility Transformation written by J. Boccio and published by . This book was released on 1972 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: An analysis of the incompressible turbulent boundary layer, developing under the combined effects of mass transfer and pressure gradient, is presented in this paper. A strip-integral method is employed whereby two of the three governing equations are obtained by integrating the combined momentum and continuity equation to 50 percent and 100 percent, respectively, of the boundary-layer height. The latter equation is the usual momentum-integral equation; the former equation requires specification of shear. Accordingly, Clauser's equilibrium eddy-viscosity law is assumed valid at this point. The third and final equation is obtained by specifying that Stevenson's velocity profiles apply throughout the domain of interest, from which a skin-friction law can be derived. Comparisons of the numerical results with the experiments of McQuaid, which include combined effects of variable pressure gradient and mass transfer, show good agreement.

Download or read book Physical and Computational Aspects of Convective Heat Transfer written by T. Cebeci and published by Springer Science & Business Media. This book was released on 2013-04-18 with total page 497 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume is concerned with the transport of thermal energy in flows of practical significance. The temperature distributions which result from convective heat transfer, in contrast to those associated with radiation heat transfer and conduction in solids, are related to velocity characteristics and we have included sufficient information of momentum transfer to make the book self-contained. This is readily achieved because of the close relation ship between the equations which represent conservation of momentum and energy: it is very desirable since convective heat transfer involves flows with large temperature differences, where the equations are coupled through an equation of state, as well as flows with small temperature differences where the energy equation is dependent on the momentum equation but the momentum equation is assumed independent of the energy equation. The equations which represent the conservation of scalar properties, including thermal energy, species concentration and particle number density can be identical in form and solutions obtained in terms of one dependent variable can represent those of another. Thus, although the discussion and arguments of this book are expressed in terms of heat transfer, they are relevant to problems of mass and particle transport. Care is required, however, in making use of these analogies since, for example, identical boundary conditions are not usually achieved in practice and mass transfer can involve more than one dependent variable.

Download or read book Numerical Investigation of Surface Curvature Effects in Compressible Turbulent Flows written by and published by . This book was released on 1994 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this work has been to develop a direct numerical simulation capability for compressible, non-canonical wall-bounded flows which is directly applicable to actual flight vehicles. Data from the simulations is used to educe information about the organized motion. In the flow and bow they are affected by the extra strain rates due to concave wall curvature. A second-order finite volume approach and both fourth-order and sixth-order compact differences are available for the spatial derivatives. The algorithm allows for generalized coordinates so that simulations about complex geometries can be performed. Extensive testing was done for two subgrid-scale models, the compressible Smagoriusky and structure function models, for a supersonic boundary layer. As the subgrid-scale viscosity also behaves as an artificial viscosity for central differencing codes, the study reinforced the need for high-order dissipation models in the simulation code. Validation of the numerical method was performed for flow over a concave surface for subsonic flow in which streamwise vortices develop in the boundary-layer due to the Gortler instability. The geometry and flow conditions closely approximated the incompressible experiments of Swearingen and Blackwelder. The simulations captured the essential features of the experiments in which counter-rotating vortices developed near the wall. As these streamwise vortices develop, the laminar boundary layer on the concave wall rapidly becomes three-dimensional. Higher-momentum fluid is pulled towards the wall from the outer flow as vortices grow downstream. The low-speed fluid lying between the vortices induces low-momentum fluid away from the wall, leading to inflectional streamwise velocity profiles, in good agreement with the experiments. (AN).

Download or read book Aspects of Turbulent Shear Layer Dynamics and Mixing written by Michael David Slessor and published by . This book was released on 1998 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experiments have been conducted in the GALCIT Supersonic Shear Layer Facility to investigate some aspects of high Reynolds number, turbulent, shear layer flows in both incompressible and compressible flow regimes. Experiments designed to address several issues were performed; effects of inflow conditions, freestream conditions (supersonic/subsonic flow), and compressibility, on both large scale dynamics and small scale mixing, are described. Chemically reacting and non reacting flows were investigated, the former relying on the (H2+NO)/F2 chemical system, in the fast-kinetic regime, to infer the structure and amount of molecular scale mixing through use of "flip" experiments. Both inflow conditions and compressibility are found to have significant effects on the flow. In particular, inflow conditions are "remembered" for long distances downstream, a sensitivity similar to that observed in low-dimensionality, nonlinear (chaotic) systems. A previously proposed mode selection rule for turbulent structure convection speeds, based on the presence of a lab frame subsonic freestream, was demonstrated to be incorrect. Compressibility, when decoupled from other parameters, e.g., Reynolds number, velocity and density ratios, reduces large scale entrainment and growth, but slightly enhances mixing, and changes the molecularly mixed fluid structure. This reduction in shear layer growth rate is examined and a new parameter that interprets compressibility as an energy exchange mechanism is proposed. The parameter reconciles and collapses experimentally observed growth rates.

Download or read book Shear stress Eddy viscosity and Mixing Length Distributions in Hypersonic Turbulent Boundary Layers written by and published by . This book was released on 1971 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Progress in Turbulence Modeling for Complex Flow Fields Including Effects of Compressibility written by David C. Wilcox and published by . This book was released on 1980 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An Experimental Investigation of Structure Mixing and Combustion in Compressible Turbulent Shear Layers microform written by Hall, Jeffery L and published by Ann Arbor, Mich. : University Microfilms International. This book was released on 1991 with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-dimensional, compressible, turbulent shear layers are studied in a new wind tunnel facility. Both reacting and non-reacting flows are investigated, with one free stream velocity supersonic and the other subsonic. The combustion experiments are based on use of low concentrations of hydrogen, nitric oxide and fluorine gases. Side-view Schlieren photographs of these reacting and non-reacting flows appear devoid of the 2-D, large scale structures seen in incompressible flow. Comparison with all-subsonic flows produced in the same facility suggests that this lack of two-dimensional structure is due to the presence of the supersonic high-speed free stream velocity. Travelling shock and expansion waves are observed in the high compressibility flows, evidently created by turbulent structures convecting at supersonic velocities. Such waves are seen only in the low-speed fluid, with apparent convection velocities much higher than those predicted on the basis of isentropic pressure-matching arguments. The measured shear layer growth rates agree with previous results by other experiments, except for a few cases at low compressibility and low density ratio. The fast chemistry regime is attained in some of the high compressibility flows tested. 'Flip' experiments conducted in this regime indicated that the volume fraction of mixed fluid in the layer is substantially reduced as compared to previous incompressible results. These same flip experiments also reveal that compressibility significantly alters the entrainment ratio.

Download or read book Signatures of Compressibility in an Annular Free shear Layer with Increasing Mach Number written by Pablo Naoki Manzano Miura and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: There has been an upsurge of interest in supersonic passenger aircraft and in soaring the skies even faster with scramjets. Turbulence plays a critical role in the mixing of air and fuel within the combustors of these vehicles, and has a direct impact on their performance. Previous research has found that flow compressibility reduces mixing, while also increasing noise and modifying dissipation. The importance of compressible turbulence in many other natural and engineered settings, including astrophysical flows and fusion reactors, suggests a broad utility for an understanding of its universal aspects. To date, the influence of compressibility on the fundamental turbulence structure and on the transfer and dissipation of energy is not fully understood. The scarcity of empirical and theoretical information about compressible turbulence can be explained by the increased mathematical difficulty, complexity of energy exchange mechanisms, and the larger parameter space. In this dissertation, we perform a detailed experimental study of the turbulence found within a novel compressible turbulence facility using hot-wire anemometry. In the first part of this work, we characterize the Variable Density and Speed of Sound Vessel (VDSSV), which produces compressible subsonic turbulent flows. By switching between working fluids with different speeds of sound (air and sulfur hexafluoride SF$_{6}$), we isolate the influence of the Mach number on turbulence statistics from the influence of the Reynolds number and boundary conditions. A ducted fan generates a turbulent jet whose mean velocity profiles approach a self-similar state. We find that the jet spreads more slowly with increasing Mach number, and that the integral length scale and Kolmogorov constant remain approximately invariant with respect to changes in either Reynolds or Mach numbers. In the second part of this work, we explore the influence of compressibility on the spatial structure of turbulence by analyzing statistics of velocity increments at inertial scales. We use Extended Self-Similarity (ESS) methods to, for instance, characterize the intermittency of the turbulence and compare our data with previous literature. Additionally, structure functions up to thirteenth-order suggest a universal behavior of turbulent fluctuations at small inertial scales in response to increases in Mach number. In the final part of this work, we use an array of loudspeakers that surround the jet to provide additional compressible motions to the turbulence. Following a brief characterization of the sound generated by these loudspeakers, we report on energy spectra and low-order structure functions, and find that the former are sensitive to the acoustic forcing when the ratio of estimated dilatational motion to solenoidal motion exceeds 0.1.