Far wake behind cylinders at hypersonic speeds. II.

Behrens, Wilhelm

doi:10.2514/3.4482

Cited by 28 publications

(18 citation statements)

References 8 publications

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“…These transition characteristics have been observed for the flat plate wake in incompressible flow 18 and for the cylinder wake in hypersonic flow. 16 The upstream movement of the location of wake transition with increasing Reynolds number has been investigated both in wind tunnels 16 These transition results also point out the existence of a minimum Reynolds number for transition below which the far wake remains laminar throughout its downstream extent. 2 Although mean flow measurements are available for the blunt body far wake in hypersonic flow 16 ' 25 ' 26 and for slender axisymmetric bodies, 27~29 there exists a lack of similar data for the slender two-dimensional body.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of far wakes behind two-dimensional slender bodies at M sub infinity equals 6

Batt

Kubota

1969

AIAA Journal

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An experimental investigation has been conducted at M^ = 6 to determine mean flow properties for far wakes behind several two-dimensional slender bodies at zero angle of attack. The adiabatic wall configurations tested included a flat-plate model and two 20° wedge models which differed by a factor of two in base height. The effect of wall temperature was examined by cooling the larger wedge model to a temperature of about two tenths of the freestream stagnation temperature. Freestream Reynolds numbers were varied from 50,000 to 200,000 per in. for each of these four configurations. Profile measurements of total temperature and Pitot pressure were combined with centerline static pressures to determine completely the far-wake flowfield from the wake neck downstream to the linear far wake. The effect of transition on mean flow properties was determined. Comparison of laminar wake data for adiabatic wall models with linear wake theory was favorable. Maximum centerline pressures in the far wake for all configurations were generally 10% higher than the freestream pressure. For the cold wall wedge the maximum centerline enthalpy for all cases occurred two base heights downstream of the model base and was triple the magnitude of the freestream enthalpy. The decay rate of enthalpy was "small" when the far wake was laminar.

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Section: Introductionmentioning

confidence: 99%

Experimental investigation of far wakes behind two-dimensional slender bodies at M sub infinity equals 6

Batt

Kubota

1969

AIAA Journal

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“…Experimental measurements of growth rates in the linear regime were obtained for a supersonic forced wake at Mach 3.7 (Kendall (7) 1962), for a far wake of cylinders at Mach 6 (Behrens (8) 1968) and for a flat plate wake at Mach 6 (Behrens & Ko (9) 1971). From comparisons made between stability theory and experiment, they showed that qualitative similarities exist between compressible and incompressible wakes.…”

Section: Introductionmentioning

confidence: 99%

Acoustic Wave Generation in a Compressible Wake

Maekawa

Takiguchi

Watanabe

2006

JSME international journal. Ser. B, Fluids and thermal engineer

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The compressible Navier-Stokes equations are numerically solved to study the acoustic generation mechanism associated with the evolution of the structure in a compressible plane wake undergoing transition to turbulence. High-order compact finite difference schemes are used for spatial derivatives and a 4th-order Runge-Kutta scheme is employed for time advancement. Navier-Stokes characteristic boundary conditions are used in the vertical direction and periodic boundary conditions in the streamwise and spanwise directions. Threedimensional structures of the wake are studied by means of temporally evolving plane wakes forced with a combination of unstable modes obtained from linear stability theory using a mapped Fourier method for the viscous compressible equations. Forcing with a pair of oblique subharmonic unstable modes yields streamwise/vertical counter-rotating vortices in the saddle region. As the streamwise/vertical vortices evolve outside, their self-induction causes inclined braidlike structures to form in the wake, which are similar to observations in the experimental supersonic flat wake transition. The oblique subharmonic unstable modes also cause the spanwise variations in the core that lead to roller distortion. Acoustic waves of plane wakes are generated when two-dimensional rollup structures appear and rotate in such wakes. Near-field sound wave pressure decreases downstream due to the three-dimensional evolution of the wake.

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“…The wavelength of structures that would be shed by a cyl inder at a Strouhal number of 0.2 is included (to scale) in these figures. There does not appear to be a correlation with the wire diameter in any of the three shots in this figure, suggesting that no regular vortex shedding typical of in compressible flows over cylinders occurs, but that the flow is similar to the observations of Behrens (1966), who noted that instabilities did not develop until much further downstream in supersonic flow. This further supports our hypothesis that the structures observed in Fig.…”

Section: An Experimental Control Studymentioning

confidence: 44%

“…Hot-wire studies in the wake of cylinders in supersonic flows have looked specifically at this problem (Behrens 1966). In these studies, the width of the outer wake behind the wire was measured and the spectrum of frequencies of instability was determined.…”

Section: The Cylinder In Supersonic Flowmentioning

confidence: 99%

Development and application of streakline visualization in hypervelocity flows

Lemieux

Hornung

2002

Exp Fluids

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In the traditional smoke-wire setup, the streak lines consist of smoke generated by oil that vaporizes as it runs down a heated wire placed upstream of a model in a wind tunnel. Provided that the wind tunnel flow has sufficiently Abstract A method for visualizing streaklines in hypervelocity flows has been developed. The method uses the high temperatures produced in hypervelocity flows to ablate small amounts of sodium deposited onto a wire stretched across the flow and to broaden the lines in the sodium spectrum. By using a dye laser, tuned to a wave length close to one of the sodium D-lines, as the light source in shadowgraph or Schlieren visualization, streaklines seeded with sodium become visible through ab sorption and/or enhanced refractivity. The technique has been used to investigate the stability of the shear layer produced by the curved bow shock on a cylindrically blunted wedge. The results suggest that the shear layer is unstable, exhibiting structures with a wavelength that is comparable to half the nose radius of the body. IntroductionA curved shock produces a shear layer with smoothly varying vorticity. The vorticity generated at the shock is a function of the shock angle, curvature, and density ratio across the shock (Hayes and Probstein 1966). A study was undertaken to investigate the stability of such shear layers, as produced by the curved bow shock on a blunt wedge in hypervelocity flows. One of the goals of this study was to use flow visualization techniques capable of highlighting instabilities in the shear layer, if these were found to exist. The idea was to duplicate the success of the smoke-wire in similar studies in subsonic flows. low turbulence, this method can be used even at super sonic speeds (Goddard et al. 1959). In stability studies in particular, the smoke-wire has proved to be a valuable research tool and is widely used in qualitative and quan titative studies (e.g., Fric and Roshko 1994). A review of the literature, however, does not reveal any successful implementation of a similar technique in the short-dura tion flows of hypervelocity shock tunnels. Streakline visualization in hypervelocity flowsVisualization using smoke is not realizable at the flow conditions typical of shock tunnels. On the other hand, Germain (1994) has been successful in applying the atomic sodium seeding method of Blendstrup et al. (1979) to visualize boundary layer flows at these conditions and provided the basis for a new flow visualization technique.The new technique, called sodium wire streakline vi sualization (SWSV), combines the method of Blendstrup et al. (1979) with the smoke-wire idea. It uses the hot gas flow of the shock tunnel to produce streaks by ablation of sodium from a wire. By tuning a narrow bandwidth light source to a frequency close to an absorption line, streaks containing sodium may be visualized through a combi nation of absorption and enhanced refractivity, depending on the difference between the line center and light source frequencies.The seeding is made relatively safe an...

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Far wake behind cylinders at hypersonic speeds. II.

Cited by 28 publications

References 8 publications

Experimental investigation of far wakes behind two-dimensional slender bodies at M sub infinity equals 6

Experimental investigation of far wakes behind two-dimensional slender bodies at M sub infinity equals 6

Acoustic Wave Generation in a Compressible Wake

Development and application of streakline visualization in hypervelocity flows

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