Download or read book Stability of Boundary Layers at High Supersonic and Hypersonic Speeds written by and published by . This book was released on 1992 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The thrust of this research program has been the improvement of our capabilities for analyzing stability and transition of boundary layers at supersonic speeds. During the first phase, our efforts were primarily directed toward analytical studies, establishing the elements of the numerical approach, and evaluating existing and new concepts to tackle the variety of problems. The second, and final, phase has been devoted to combining selected elements into codes, verification of these codes, comparison with previous results, and computing the basic flow over realistic geometries. The latter task has consumed the bulk of our resources. Analytical and numerical studies have been performed to investigate the role of the shock on both stability and receptivity characteristics of the flow. Development of the parabolized stability equations (PSE) for compressible flows has been a major goal. A new code incorporating many of the latest concepts and open to extensions is largely completed.
Download or read book Stability and Transition of Hypersonic Boundary Layer Flows written by and published by . This book was released on 1992 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Final Report describes our research of hypersonic and supersonic boundary-layer flows. In spite of its extreme importance to the accurate prediction of drag and heating requirements in high-speed flow, the study of boundary-layer transition in hypersonic (NASP) and supersonic (fighter and high-speed civil transport) flows is still very much in its infancy. Transition is well known, however, to depend strongly on such effects as pressure gradient, wall curvature, sweep, roughness, wall mass transfer, freestream and wall temperature, nose radius, nonequilibrium chemistry, and freestream disturbances. (These effects have been discussed in any number of workshops and U.S. Transition Study Group meetings under the direction of Eli Reshotko.) We have completed detailed studies of the stability of the laminar basic state of 2-D and axisymmetric boundary layers with non-equilibrium chemistry included and 3-D boundary-layer flows of an ideal gas. (Relatively simple geometries were considered due to the anticipated difficulties in performing basic-state analyses.).
Download or read book A Review of High speed Convective Heat transfer Computation Methods written by Michael E. Tauber and published by . This book was released on 1989 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Effects of Wing Plan Form on the Static Longitudinal Aerodynamic Characteristics of a Flat top Hypersonic Aircraft at Mach Numbers from 0 6 to 1 4 written by Stuart L. Treon and published by . This book was released on 1960 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
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.
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:
Download or read book Receptivity and Stability of Supersonic and Nonequilibrium Hypersonic Boundary Layers written by Yanbao Ma and published by . This book was released on 2004 with total page 858 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studies of Hypersonic Boundary Layer Behavior written by A. J. Smits and published by . This book was released on 1995 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
Download or read book The Stability of Laminar Boundary Layer at the Supersonic Speeds of Flow written by M. A. Alekseev and published by . This book was released on 1975 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of Distributed Three dimensional Roughness and Surface Cooling on Boundary layer Transition and Lateral Spread of Turbulence at Supersonic Speeds written by Albert L. Braslow and published by . This book was released on 1959 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Experimental Study of Boundary layer Transition at Supersonic and Hypersonic Speeds written by Jack D. Whitfield and published by . This book was released on 1960 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Analysis of the Three dimensional Compressible Turbulent Boundary Layer on a Sharp Cone at Incidence in Supersonic and Hypersonic Flow written by John C. Adams and published by . This book was released on 1972 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt: An analytical approach toward numerical calculation of the three-dimensional turbulent boundary layer on a sharp cone at incidence under supersonic and hypersonic flow conditions is presented. The theoretical model is based on implicit finite-difference integration of the governing three-dimensional turbulent boundary-layer equations in conjunction with a three-dimensional scalar eddy-viscosity model of turbulence. Comparison is made of present theory with detailed experimental measurements of the three-dimensional turbulent boundary-layer structure (velocity and temperature profiles), the surface streamline direction (obtained via an oil-flow technique) and surface heat-transfer rate.
Download or read book On the Nonlinear Stability of a High speed Axisymmetric Boundary Layer written by Institute for Computer Applications in Science and Engineering and published by . This book was released on 1991 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: The stability of a high speed, axisymmetric boundary layer is investigated using secondary instability theory and direct numerical simulation. Parametric studies based on temporal secondary instability theory identify subharmonic secondary instability as a likely path to transition on a cylinder at Mach 4.5. The theoretical predictions are validated by direct numerical simulation of temporally-evolving primary and secondary disturbances in an axisymmetric boundary-layer flow. At small amplitudes of the secondary disturbance, predicted growth rates agree to several significant digits with values obtained from the spectrally-accurate solution of the compressible Navier Stokes equations. Qualitative agreement persists to large amplitudes of secondary disturbance. Moderate transverse curvature is shown to significantly affect the growth rate of axisymmetric second mode disturbances, the likely candidates of primary instability. The influence of curvature on secondary instability is largely indirect but most probably significant, through modulation of the primary disturbance amplitude. Subharmonic secondary instability is shown to be predominantly inviscid in nature, and to account for spikes in the Reynolds stress components at or near the critical layer.
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 Boundary Layer Transition in the Leading Edge Region of a Swept Cylinder in High Speed Flow written by Colin Phillip Coleman and published by . This book was released on 1998 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt:
