The formation of a three-dimensional wave packet in the boundary layer on a plate for high Reynolds numbers

1989 ◽  
Vol 29 (4) ◽  
pp. 200-203
Author(s):  
I.V. Savenkov
Keyword(s):  
Boundary Layer ◽  
Wave Packet ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
High Reynolds Numbers ◽  
High Reynolds ◽  
Dimensional Wave

On displacement-thickness, wall-layer and mid-flow scales in turbulent boundary layers, and slugs of vorticity in channel and pipe flows

1990 ◽  
Vol 428 (1875) ◽  
pp. 255-281 ◽  
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Wall Layer ◽  
Amplitude Dependence ◽  
Thin Wall ◽  
Pipe Flows ◽  
High Reynolds Numbers ◽  
High Reynolds

This theoretical study is motivated by the experimental observations ( a ) on the thickening of a turbulent boundary layer compared with its laminar counterpart, ( b ) on the erupting tongue of fluid that forms the leading edge of a turbulent spot in a boundary layer, ( c ) on the wall-layer and mid-flow scales, and ( d ) on the slugs of vorticity that occur in the middle of turbulent channel and pipe flows. It appears that no previous rational explanation has been put forward for these experimental observations. The present tentative suggestions for ( a ), ( b ) and ( d ) centre on the existence of small-deficit fast-travelling zones of concentrated vorticity governed by the nonlinear Euler equations to leading order at high Reynolds numbers Re but crucially influenced by viscosity nevertheless. In the boundary-layer case these zones travel outside the original boundary layer and hence act to increase the effective boundary-layer thickness. The structure of such zones and their scales, governing equations and amplitude dependence are discussed for assumed planar boundary layers and channel flows and for three-dimensional pipe flows in turn. Allied with this, the theory addresses the closure of the amplitude-dependent neutral curve at high Reynolds numbers, the connection with other Euler-type flows and the possibility of delay in sublayer bursting, as well as aiming to give some guidance on nonlinear aspects of unsteady two- and three-dimensional computations for Euler and related flows. The aspects in ( c ) above, concerning the turbulent scales both of the thin wall layer ( O ( Re -1 In Re ), from a renormalizing and scale-cascade argument) and of the thicker mid-flow zone (containing the Kolmogorov microscale O ( Re -3/4 )) which lies between that layer and the extensive small-deficit outer zone, are also discussed tentatively in terms of their dynamics, leading to apparently good agreement with turbulent-flow experiments and empirical models, for those scales. Other qualitative comparisons are presented.

Streamwise absolute instability of a three-dimensional boundary layer at high Reynolds numbers

1998 ◽  
Vol 373 ◽  
pp. 111-153 ◽  
Author(s):  
OLEG S. RYZHOV ◽  
EUGENE D. TERENT'EV
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Wave Packets ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Absolute Instability ◽  
Streamwise Direction ◽  
High Reynolds Numbers ◽  
Dimensional Boundary ◽  
High Reynolds

The simplest receptivity problem of linear disturbances artificially excited in a three-dimensional boundary layer adjacent to a solid surface is studied in the framework of the generalized triple-deck theory. In order to provide a mathematical model to be compared with experimental data from wind-tunnel tests we consider the base flow over a swept flat plate. Then crossflow in the near-wall region originates owing to an almost constant pressure gradient induced from outside with a displacement body on top. A pulsed or vibrating ribbon installed on the solid surface serves as an external agency provoking initially weak pulsations. A periodic dependence of the ribbon shape on a coordinate normal to the streamwise direction makes the receptivity problem effectively two-dimensional, thereby allowing a rigorous analysis to be carried out without additional assumptions.The most striking result from the asymptotic theory is the discovery of streamwise absolute instability intrinsic to a three-dimensional boundary layer at high Reynolds numbers. However, due to limitations imposed on the receptivity problem no definite conclusions can be made with regard to possible continued convection of disturbances in the crossflow direction. An investigation of the dispersion-relation roots points to the fact that wave packets of different kinds can be generated by an external source operating in the pulse mode. Rapidly growing wave packets sweep downstream, weaker wave packets move against the oncoming stream. Insofar as the amplitude of all of the modulated signals increases exponentially in time and space, the excitation process gives rise to absolutely unstable disturbances in the streamwise direction. The computation confirms the theoretical prediction about the existence of upstream-advancing wave packets. They can be prevented from being persistently amplified only in a region ahead of the ribbon where nearly critical values of the Reynolds number are attained.The results achieved are shown to be broadly consistent with wind-tunnel measurements. Hence a conjecture is made that the onset of transition is probably associated, under some environmental conditions, with the mechanism of streamwise absolute instability in the supercritical range of the Reynolds numbers.

Effects of Reynolds Number and Free-Stream Turbulence on Boundary Layer Transition in a Compressor Cascade

2000 ◽  
Author(s):  
Heinz-Adolf Schreiber ◽  
Wolfgang Steinert ◽  
Bernhard Küsters
Keyword(s):  
Boundary Layer ◽  
Free Stream ◽  
Reynolds Numbers ◽  
Boundary Layer Transition ◽  
Bypass Transition ◽  
Layer Transition ◽  
Free Stream Turbulence ◽  
High Reynolds Numbers ◽  
High Turbulence ◽  
High Reynolds

An experimental and analytical study has been performed on the effect of Reynolds number and free-stream turbulence on boundary layer transition location on the suction surface of a controlled diffusion airfoil (CDA). The experiments were conducted in a rectilinear cascade facility at Reynolds numbers between 0.7 and 3.0×106 and turbulence intensities from about 0.7 to 4%. An oil streak technique and liquid crystal coatings were used to visualize the boundary layer state. For small turbulence levels and all Reynolds numbers tested the accelerated front portion of the blade is laminar and transition occurs within a laminar separation bubble shortly after the maximum velocity near 35–40% of chord. For high turbulence levels (Tu > 3%) and high Reynolds numbers transition propagates upstream into the accelerated front portion of the CDA blade. For those conditions, the sensitivity to surface roughness increases considerably and at Tu = 4% bypass transition is observed near 7–10% of chord. Experimental results are compared to theoretical predictions using the transition model which is implemented in the MISES code of Youngren and Drela. Overall the results indicate that early bypass transition at high turbulence levels must alter the profile velocity distribution for compressor blades that are designed and optimized for high Reynolds numbers.

Temperature Control of Blow-Down, Supersonic Tunnels

1956 ◽  
Vol 60 (541) ◽  
pp. 67-70
Author(s):  
T. A. Thomson
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Mach Number ◽  
Reynolds Numbers ◽  
Stagnation Temperature ◽  
Blow Down ◽  
High Reynolds Numbers ◽  
Experimental Errors ◽  
High Reynolds

The blow-down type of intermittent, supersonic tunnel is attractive because of its simplicity and because relatively high Reynolds numbers can be obtained for a given size of test section. An adverse characteristic, however, is the fall of stagnation temperature during runs, which can affect experiments in several ways. The Reynolds number varies and the absolute velocity is not constant, even if the Mach number and pressure are; heat-transfer cannot be studied under controlled conditions and the experimental errors arising from the effect of heat-transfer on the boundary layer vary in time. These effects can become significant in quantitative experiments if the tunnel is large and the variation of temperature very rapid; the expense required to eliminate them might then be justified.

Experiments on the Flow Around a Sphere at High Reynolds Numbers

1969 ◽  
Vol 36 (3) ◽  
pp. 598-607 ◽  
Author(s):  
T. Maxworthy
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Pressure Distribution ◽  
Reynolds Numbers ◽  
Boundary Layer Separation ◽  
Recirculation Region ◽  
Layer Separation ◽  
High Reynolds Numbers ◽  
High Reynolds

Flow around a sphere for Reynolds numbers between 2 × 105 and 6 × 104 has been observed by measuring the pressure distribution around a circle of longitude under a variety of conditions. These include the effects of laminar and turbulent boundary layer separation, tunnel blockage, various boundary layer trip arrangements and inserting an object to disrupt the unsteady, recirculation region behind the sphere.

Experimental Investigation of Turbulent Boundary Layer Over Smooth Flat Plate With Towing Tank: Attempt of Measurement of Frictional Stress

2007 ◽  
Author(s):  
Kiyoto Mori ◽  
Hiroki Imanishi ◽  
Yoshiyuki Tsuji ◽  
Masashi Kashiwagi ◽  
Masaru Inada ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Frictional Resistance ◽  
Reynolds Numbers ◽  
Sufficient Accuracy ◽  
Frictional Stress ◽  
Towing Tank ◽  
High Reynolds Numbers ◽  
Pressure Resistance ◽  
High Reynolds

The purpose of this study is to evaluate the frictional resistance with sufficient accuracy and to evaluate the drag coefficient at high Reynolds numbers. We have measured the resistance of flat plate with using a towing tank. Correcting the wave-making resistance, pressure resistance, and drag on turbulence simulator, it is found that the measured frictional resistance is smaller than the Karman-Schoenherr formula. But it agrees with the values suggested by Osaka et. al and Osterlund et. al.

Sign in / Sign up

Export Citation Format

Share Document