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Relationship Between Transition And Modes Of Instability In Supersonic Boundary Layers
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Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781722728496 Total Pages :30 pages Book Rating :4.7/5 (284 download)
Book Synopsis Relationship Between Transition and Modes of Instability in Supersonic Boundary Layers by : National Aeronautics and Space Administration (NASA)
Download or read book Relationship Between Transition and Modes of Instability in Supersonic Boundary Layers written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-11 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: The relationship between the predicted transition location and the first and second modes of instability in two-dimensional supersonic boundary-layer flow on a flat plate is examined. Linear stability theory and the N-factor criterion are used to predict transition location. The effect of heat transfer is also studied; the results demonstrate that the transition reversal phenomenon can be explained by the opposite effect of cooling on the first and second modes of instability. Compressibility of destabilizing at free-stream Mach numbers of 2 to 3.5. The predicted transition location is due to the oblique first modes of instability, up to free-stream Mach numbers between 6 and 6.5. At higher Mach numbers, the predicted transition location is due to a combination of two-dimensional first and second modes of instability. Masad, Jamal A. Unspecified Center NAS1-19299; RTOP 537-03-23-03...
Book Synopsis Relationship Between Transition and Modes of Instability in Supersonic Boundary Layers by : Jamal A. Masad
Download or read book Relationship Between Transition and Modes of Instability in Supersonic Boundary Layers written by Jamal A. Masad and published by . This book was released on 1993 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Instability and Transition in Three-dimensional Supersonic Boundary Layers by : M. R. Malik
Download or read book Instability and Transition in Three-dimensional Supersonic Boundary Layers written by M. R. Malik and published by . This book was released on 1992 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 602 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Book Synopsis Receptivity and Transition to Turbulence of Supersonic Boundary Layers with Surface Roughness by : Nicola De Tullio
Download or read book Receptivity and Transition to Turbulence of Supersonic Boundary Layers with Surface Roughness written by Nicola De Tullio and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A deeper understanding of the different factors that influence the laminar-turbulent transition in supersonic boundary layers will help the design of efficient high-speed vehicles. In this work we study the effects of surface roughness on the stability and transition to turbulence of supersonic boundary layers. The investigation is carried out by direct numerical simulations (DNS) of the compressible Navier-Stokes equations and focuses on the modifications introduced in the transition process by localised roughness elements, for Mach numbers M∞ = 6.0 and M∞ = 2.5, and distributed slender pores at M∞ = 6.0. The first part of the investigation into the effects of localised roughness deals with the receptivity and initial exponential amplification of disturbances in boundary layers subjected to small external perturbations. Different transition scenarios are investigated by considering different free-stream disturbances and roughness elements with different heights. The results show that, for roughness heights approaching the local displacement thickness, transition is dominated by the growth of a number of instability modes in the roughness wake. These modes are damped by wall cooling and their receptivity is found to be more efficient in the case of free-stream disturbances dominated by sound. At M∞ = 6 the growth of Mack modes in the boundary layer is found to play a crucial role in the excitation of the most unstable wake modes. An investigation into the nonlinear stages of transition shows that the breakdown to turbulence starts with nonlinear interactions of the wake instability modes. This leads to the formation of a turbulent wedge behind the roughness element, which spreads laterally following mechanisms similar to those observed for the evolution of compressible turbulent spots. An oblique shock impinging on the transitional boundary layer significantly accelerates the breakdown process and leads to a wider turbulent wedge. The study ends with an analysis of porous walls as a passive method for transition control, which is carried out using a temporal DNS approach. The results show damping of both the primary, of second or Mack mode type, and secondary instabilities and indicate that, despite the high Mack number, first mode waves regain importance in this modified transition scenario.
Book Synopsis Supersonic Unstable Modes in Hypersonic Boundary Layers with Thermochemical Nonequilibrium Effects by : Carleton Knisely
Download or read book Supersonic Unstable Modes in Hypersonic Boundary Layers with Thermochemical Nonequilibrium Effects written by Carleton Knisely and published by . This book was released on 2018 with total page 221 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mack's second mode has been known to be the dominant disturbance leading to transition to turbulence in traditional hypersonic boundary layer flows at zero angle of attack. Physically, the second mode exists due to trapped acoustic waves within the boundary layer. The second mode has been widely studied and the conditions that stabilize or amplify the second mode are well documented. Predicting the second mode amplification is the basis of contemporary transition prediction techniques such as the eN method. There has been a renewed interest in studying hypersonic boundary layer stability in high-enthalpy flows with highly-cooled walls due to its applicability to experiments and some real flight conditions. One physical phenomenon that occurs in these flows is the creation of a supersonic mode, which is associated with an unstable mode F1 synchronizing with the slow acoustic spectrum. This causes the disturbance to travel upstream supersonically relative to the mean flow outside the boundary layer and radiate sound away from the boundary layer. The supersonic mode has been known to exist for decades, but has until recently been deemed negligible in comparison to the second mode. However, a resurgence in interest in the supersonic mode has shown the supersonic mode to exist in unexpected conditions with considerable peak growth rates compared to the second mode. Namely, recent research in the field has shown the supersonic mode in hot-wall flows, upending the notion that it is an artifact of highly-cooled walls. Additionally, a dominant supersonic mode with significantly larger growth rate than the second mode has been found on very blunt cones. Therefore, because the supersonic mode has not been systematically investigated, the mechanism of its creation and the conditions under which it exists are not yet clear. The objective of this work is to systematically investigate the supersonic mode using numerical and theoretical tools to simulate hypersonic flow over blunt cones. Specifically, this work aims to (1) Determine the characteristics of the supersonic mode and under what conditions it exists, (2) Explore the effectiveness of Linear Stability Theory (LST) on predicting the supersonic mode, and (3) Examine the impact of the supersonic mode on transition to turbulence under realistic flight or experimental conditions. This work explores the supersonic mode on a 1 mm nose radius cone in various free stream flow configurations with a 5-species, two-temperature nonequilibrium gas model for air. A combined approach of Direct Numerical Simulation (DNS) and Linear Stability Theory (LST) are used to numerically investigate the supersonic mode. New LST equations with linearized Rankine-Hugoniot shock relation boundary conditions are derived and verified. In addition, a theoretical schematic has been developed to aid future experimentalists and those performing DNS in visualizing the supersonic mode. Mach numbers of 5 and 10 are considered with wall-temperature-to-free-stream-temperature ratios (Tw/T ) between 0.2 and 1.43. Additionally, the impact of thermochemical nonequilibrium on the supersonic mode is assessed. Both LST and DNS results have confirmed the existence of the supersonic mode on a Mach 5 axisymmetric cold-wall (Tw/T = 0.2) cone. On a warmer wall (Tw/T = 0.667) under the same free stream conditions, LST indicated the supersonic mode was stabilized, although some weak sound radiation was still apparent in DNS. For the Mach 10 case, LST predicted a stable supersonic mode for both wall temperature cases (Tw/T = 1.43, Tw/T = 0.43), however a prominent supersonic mode was observed in DNS. The supersonic mode was determined to be excited via a modal interaction that is ignored in LST due to the independent mode assumption. Furthermore, the supersonic mode in the Mach 10 case with Tw/T = 0.43 exhibited a stronger peak growth rate for the supersonic mode compared to Mack's traditional second mode. These findings illustrate the need for combined LST and DNS studies of the supersonic mode. Overall, this study has determined that the supersonic mode is destabilized by largely the same factors as Mack's second mode. Namely, wall cooling is destabilizing, increasing Mach number/stagnation enthalpy is destabilizing, and vibrational nonequilibrium is stabilizing. The impact of chemical nonequilibrium is hypothesized to be slightly destabilizing, although was not able to be confirmed with the cases explored here. Based on the results presented here, transition prediction analyses relying on LST, such as the eN method, should be used with caution when applied to the supersonic mode, as it has been shown that LST may not fully capture the mechanism of the supersonic mode's creation.
Book Synopsis IUTAM Symposium on Nonlinear Instability and Transition in Three-Dimensional Boundary Layers by : Peter W. Duck
Download or read book IUTAM Symposium on Nonlinear Instability and Transition in Three-Dimensional Boundary Layers written by Peter W. Duck and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most fluid flows of practical importance are fully three-dimensional, so the non-linear instability properties of three-dimensional flows are of particular interest. In some cases the three-dimensionality may have been caused by a finite amplitude disturbance whilst, more usually, the unperturbed state is three-dimensional. Practical applications where transition is thought to be associated with non-linearity in a three- dimensional flow arise, for example, in aerodynamics (swept wings, engine nacelles, etc.), turbines and aortic blood flow. Here inviscid `cross-flow' disturbances as well as Tollmien-Schlichting and Görtler vortices can all occur simultaneously and their mutual non-linear behaviour must be understood if transition is to be predicted. The non-linear interactions are so complex that usually fully numerical or combined asymptotic/numerical methods must be used. Moreover, in view of the complexity of the instability processes, there is also a growing need for detailed and accurate experimental information. Carefully conducted tests allow us to identify those elements of a particular problem which are dominant. This assists in both the formulation of a relevant theoretical problem and the subsequent physical validation of predictions. It should be noted that the demands made upon the skills of the experimentalist are high and that the tests can be extremely sophisticated - often making use of the latest developments in flow diagnostic techniques, automated high speed data gathering, data analysis, fast processing and presentation.
Book Synopsis Instability, Transition, and Turbulence by : M.Y. Hussaini
Download or read book Instability, Transition, and Turbulence written by M.Y. Hussaini and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 626 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains the proceedings of the Workshop on In stability, Transition and Turbulence, sponsored by the Institute for Computer Applications in Science and Engineering (ICASE) and the NASA Langley Research Center (LaRC), during July 8 to August 2, 1991. This is the second workshop in the series on the subject. The first was held in 1989, and its proceedings were published by Springer-Verlag under the title "Instability and Transition" edited by M. Y. Hussaini and R. G. Voigt. The objectives of these work shops are to i) expose the academic community to current technologically im portant issues of transition and turbulence in shear flows over the entire speed range, ii) acquaint the academic community with the unique combination of theoretical, computational and experimental capabilities at LaRC and foster interaction with these capabilities, and iii) accelerate progress in elucidating the fundamental phenomena of transition and turbulence, leading to improved transition and turbulence modeling in design methodologies. The research areas covered in these proceedings include receptiv ity and roughness, nonlinear theories of transition, numerical simu lation of spatially evolving flows, modelling of transitional and fully turbulent flows as well as some experiments on instability and tran sition. In addition a one-day mini-symposium was held to discuss 1 recent and planned experiments on turbulent flow over a backward facing step.
Book Synopsis Some Effects of Leading-edge Sweep on Boundary-layer Transition at Supersonic Speeds by : Gary T. Chapman
Download or read book Some Effects of Leading-edge Sweep on Boundary-layer Transition at Supersonic Speeds written by Gary T. Chapman and published by . This book was released on 1961 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Nonparallel Instability of Supersonic and Hypersonic Boundary Layers by : Nabil M. El-Hady
Download or read book Nonparallel Instability of Supersonic and Hypersonic Boundary Layers written by Nabil M. El-Hady and published by . This book was released on 1991 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Stability of Boundary Layers at High Supersonic and Hypersonic Speeds by : Thorwald Herbert
Download or read book Stability of Boundary Layers at High Supersonic and Hypersonic Speeds written by Thorwald Herbert and published by . This book was released on 1991 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Controlled Experiments on Instabilities and Transition to Turbulence in Supersonic Boundary Layers by : T. C. Corke
Download or read book Controlled Experiments on Instabilities and Transition to Turbulence in Supersonic Boundary Layers written by T. C. Corke and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Comments on Hypersonic Boundary-layer Transition by : Kenneth F. Stetson
Download or read book Comments on Hypersonic Boundary-layer Transition written by Kenneth F. Stetson and published by . This book was released on 1990 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is a survey paper on the subject of hypersonic boundary-layer transition. Part 1 discusses boundary-layer stability theory, hypersonic boundary-layer stability experiments, and a comparison between theory and experiment. Part 2 contains comments on how many configuration and flow parameters influence transition. Part 3 discusses some additional general aspects of transition. Part 4 discusses problems of predicting transition and comments on three prediction methods. Part 5 contains some general guidelines for prediction methodology. Keywords: Boundary layer transition, Boundary layer stability, Hypersonic boundary layers.
Book Synopsis Laminar Turbulent Transition in a Hypersonic Boundary Layer. Receptivity and Instability Pre-History by :
Download or read book Laminar Turbulent Transition in a Hypersonic Boundary Layer. Receptivity and Instability Pre-History written by and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report results from a contract tasking Moscow Inst. of Physics and Technology as follows: The contractor will perform research in accordance with contractor's proposal entitled, 'Laminar-Turbulent Transition in an Hypersonic Boundary Layer.' This report addresses the initial phase of hypersonic boundary-layer transition comprising excitation of unstable normal modes and their downstream evolution from receptivity regions to the instability growth onset (instability pre-history problem). It is shown that this phase is more complicated than in subsonic and moderate supersonic cases due to the following features of the disturbance field: (1) the first and second modes are synchronized with acoustic waves near the body nose region; (2) further downstream the first mode is synchronized with entropy/vorticity waves; (3) near the instability growth onset the first mode is synchronized with the second mode. Disturbance behavior in the synchronism regions (2) and (3) are studied using the multiple-mode method, which accounts for interaction between modes of discrete and continuous spectrum due to nonparallel effects of the mean flow. It is shown that vorticity/entropy waves are partially swallowed by the boundary layer and effectively generate the first mode due to Synchronism (2). This mechanism can compete with the leading edge receptivity to the freestream acoustic waves in cases of 'quiet' freestream conditions and conical body configurations. The inter-mode exchange rule coupling input and output characteristics of the first and second modes crossing the branch point vicinity was established. Combination of the receptivity estimates related to Synchronism (2) and the inter-mode exchange rule related to Synchronism; (3) allows the evaluation of instability initial amplitudes required for the PSE calculations of the transition onset point.
Book Synopsis Instability and Transition by : M.Y. Hussaini
Download or read book Instability and Transition written by M.Y. Hussaini and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt: These two volumes contain the proceedings of the workshop on the Institute for Computer Instability and Transition, sponsored by Applications in Science and Engineering (ICASE) and the Langley Research Center (LaRC), during May 15 to June 9, 1989. The work shop coincided with the initiation of a new, focused research pro gram on instability and transition at LaRC. The objectives of the workshop were to (i) expose the academic community to current technologically important issues of instability and transition in shear flows over the entire speed range, (ii) acquaint the academic com munity with the unique combination of theoretical, computational and experimental capabilities at LaRC and foster interaction with these facilities, (iii) review current state-of-the-art and propose fu ture directions for instability and transition research, (iv) accelerate progress in elucidating basic understanding of transition phenomena and in transferring this knowledge into improved design methodolo gies through improved transition modeling, and (v) establish mech anisms for continued interaction. The objectives (i) to (iii) were of course immediately met. It is still premature to assess whether ob jectives (iv) and (v) are achieved. The workshop program consisted of tutorials, research presenta tions, panel discussions, experimental and computational demonstra tions, and collaborative projects.
Book Synopsis Boundary-layer Transition Study of Several Pointed Bodies of Revolution at Supersonic Speeds by : William A. Cassels
Download or read book Boundary-layer Transition Study of Several Pointed Bodies of Revolution at Supersonic Speeds written by William A. Cassels and published by . This book was released on 1970 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: Boundary-layer transition by the sublimation and impact-pressure techniques and force tests have been performed on three Haack-Adams bodies of revolution of fineness ratios 7, 10, and 13 at zero angle of attack for free-stream Mach numbers of 2.00, 2.75, and 4.63 and a range of Reynolds numbers based on model length of 6 to 15 X 10(to the 6 power) with and without a roughness strip. The grit method of inducing turbulence was found to provide for a nearly complete turbulent flow over the models at the lower Mach numbers and higher Reynolds numbers considered in this study while the amount of trip drag was less than 8 percent of the model drag with transition fixed. A method of interpreting sublimation data was discussed and used and the results compared well with the impact-pressure results.
Book Synopsis Instability and Transition by : M.Y. Hussaini
Download or read book Instability and Transition written by M.Y. Hussaini and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 509 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ability to predict and control viscous flow phenomena is becoming increasingly important in modern industrial application. The Instability and Transition Workshop at Langley was extremely important in help§ ing the scientists community to access the state of knowledge in the area of transition from laminar to turbulent flow, to identify promising future areas of research and to build future interactions between researchers worldwide working in the areas of theoretical, experimental and computational fluid and aero dynamics. The set of two volume contains panel discussions and research contribution with the following objectives: (1) expose the academic community to current technologically important issues of instability and transitions in shear flows over the entire speed range, (2) acquaint the academic community with the unique combination of theoretical, computational and experimental capabilities at LaRC and foster interaction with these facilities. (3) review current state-of-the-art and propose future directions for instability and transition research, (4) accelerate progress in elucidating basic understanding of transition phenomena and in transferring this knowledge into improved design methodologies through improved transition modeling, and (5) establish mechanism for continued interaction.
