Boundary-Layer Stability and Transition on a Flared Cone in a Mach 6 Quiet Wind Tunnel PDF Download
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Author: Jerrod William Hofferth
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
A key remaining challenge in the design of hypersonic vehicles is the incomplete understanding of the process of boundary-layer transition. Turbulent heating rates are substantially higher than those for a laminar boundary layer, and large uncertainties in transition prediction therefore demand conservative, inefficient designs for thermal protection systems. It is only through close collaboration between theory, experiment, and computation that the state of the art can be advanced, but experiments relevant to flight require ground-test facilities with very low disturbance levels. To enable this work, a unique Mach 6 low-disturbance wind tunnel, previously of NASA Langley Research Center, is established within a new pressure-vacuum blow-down infrastructure at Texas A&M. A 40-second run time at constant conditions enables detailed measurements for comparison with computation. The freestream environment is extensively characterized, with a large region of low-disturbance flow found to be reliably present for unit Reynolds numbers Re
Author: Jerrod William Hofferth
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
A key remaining challenge in the design of hypersonic vehicles is the incomplete understanding of the process of boundary-layer transition. Turbulent heating rates are substantially higher than those for a laminar boundary layer, and large uncertainties in transition prediction therefore demand conservative, inefficient designs for thermal protection systems. It is only through close collaboration between theory, experiment, and computation that the state of the art can be advanced, but experiments relevant to flight require ground-test facilities with very low disturbance levels. To enable this work, a unique Mach 6 low-disturbance wind tunnel, previously of NASA Langley Research Center, is established within a new pressure-vacuum blow-down infrastructure at Texas A&M. A 40-second run time at constant conditions enables detailed measurements for comparison with computation. The freestream environment is extensively characterized, with a large region of low-disturbance flow found to be reliably present for unit Reynolds numbers Re
Author: National Aeronautics and Space Adm Nasa
Publisher:
ISBN: 9781731266217
Category :
Languages : en
Pages : 134
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Book Description
An experimental investigation of the effects of angle of attack on hypersonic boundary-layer stability on a flared-cone model was conducted in the low-disturbance Mach-6 Nozzle-Test Chamber Facility at NASA Langley Research Center. This unique facility provided a 'quiet' flow test environment which is well suited for stability experiments because the low levels of freestream 'noise' minimize artificial stimulation of flow-disturbance growth. Surface pressure and temperature measurements documented the adverse-pressure gradient and transition-onset location. Hot-wire anemometry diagnostics were applied to identify the instability mechanisms which lead to transition. In addition, the mean flow over the flared-cone geometry was modeled by laminar Navier-Stokes computations. Results show that the boundary layer becomes more stable on the windward ray and less stable on the leeward ray relative to the zero-degree angle-of-attack case. The second-mode instability dominates the transition process at a zero-degree angle of attack, however, on the windward ray at an angle of attack this mode was completely stabilized. The less-dominant first-mode instability was slightly destabilized on the windward ray. Non-linear mechanisms such as saturation and harmonic generation are identified from the flow-disturbance bispectra. Doggett, Glen P. and Chokani, Ndaona Langley Research Center ANGLE OF ATTACK; AERODYNAMIC NOISE; ZERO ANGLE OF ATTACK; BOUNDARY LAYER STABILITY; HYPERSONIC SPEED; NAVIER-STOKES EQUATION; HYPERSONICS; AERODYNAMIC STABILITY; HYPERSONIC BOUNDARY LAYER; WIND TUNNELS; VELOCITY MEASUREMENT; TEST CHAMBERS; LOW NOISE...
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781724242556
Category :
Languages : en
Pages : 232
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Book Description
Hypersonic boundary layer measurements over a flared cone were conducted in a Mach 6 quiet wind tunnel at a freestream unit Reynolds number of 2.82 million/ft. This Reynolds number provided laminar-to-transitional flow over the cone model in a low-disturbance environment. Four interchangeable nose-tips, including a sharp-tip, were tested. Point measurements with a single hot-wire using a novel constant voltage anemometer were used to measure the boundary layer disturbances. Surface temperature and schlieren measurements were also conducted to characterize the transitional state of the boundary layer and to identify instability modes. Results suggest that second mode disturbances were the most unstable and scaled with the boundary layer thickness. The second mode integrated growth rates compared well with linear stability theory in the linear stability regime. The second mode is responsible for transition onset despite the existence of a second mode subharmonic. The subharmonic disturbance wavelength also scales with the boundary layer thickness. Furthermore, the existence of higher harmonics of the fundamental suggests that nonlinear disturbances are not associated with 'high' free stream disturbance levels. Nose-tip radii greater than 2.7% of the base radius completely stabilized the second mode. Lachowicz, Jason T. and Chokani, Ndaona Langley Research Center NASA-CR-198272, NAS 1.26:198272 NCC1-183; RTOP-505-59-50-02...
Author: Alan E. Blanchard
Publisher:
ISBN:
Category : Aerodynamics, Hypersonic
Languages : en
Pages : 120
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Book Description
One of the primary reasons for developing quiet tunnels is for the investigation of high-speed boundary-layer stability and transition phenomena without the transition-promoting effects of acoustic radiation from tunnel walls. In this experiment, a flared-cone model under adiabatic- and cooled-wall conditions was placed in a calibrated, "quiet" Mach 6 flow and the stability of the boundary layer was investigated using a prototype constant-voltage anemometer. The results of this experiment were compared with linear-stability theory predictions and good agreement was found in the prediction of second-mode frequencies and growth. In addition, the same "N = 10" criterion used to predict boundary-layer transition in subsonic, transonic, and supersonic flows was found to be applicable for the hypersonic flow regime as well. Under cooled-wall conditions, a unique set of continuous spectra data was acquired that documents the linear, nonlinear, and breakdown regions associated with the transition of hypersonic flow under low-noise conditions
Author: Spencer Sherwin
Publisher: Springer Nature
ISBN: 3030679020
Category : Computers
Languages : en
Pages : 809
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Book Description
This volume comprises the carefully revised papers of the 9th IUTAM Symposium on Laminar-Turbulent Transition, held at the Imperial College, London, UK, in September 2019. The papers focus on the leading research in understanding transition to turbulence, which is a challenging topic of fluid mechanics and arises in many modern technologies as well as in nature. The proceedings are of interest for researchers in fluid mechanics and industry who have to handle these types of problems, such as in the aeronautical sector.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Jason Thomas Lachowicz
Publisher:
ISBN:
Category :
Languages : en
Pages : 232
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Book Description
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: Zonglin Jiang
Publisher: Cambridge University Press
ISBN: 1009035673
Category : Technology & Engineering
Languages : en
Pages : 316
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Book Description
Introducing the state-of-the-art of hypervelocity shock tunnels, this complete reference features a variety of drivers and step-by-step introductions to their theories, physics, methods and testing. This book enables researchers and engineers in aerospace to design and improve wind tunnels that simulate flow qualities of real hypersonic flyers.
Author: J. Leith Potter
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 36
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Book Description
The feasibility of determining Reynolds numbers of boundary layer transition on sharp, 10-deg, semiangle cones at slightly supersonic free-stream Mach numbers, 1.04 = or
