A Method for Determining the Effect of Initial Boundary Layer on Turbulent Free Shear Layer Velocity Profiles

1971 ◽  
Vol 93 (4) ◽  
pp. 713-715 ◽  
Author(s):  
F. Justin Camarata
Keyword(s):  
Boundary Layer ◽  
Shear Layer ◽  
Initial Boundary ◽  
Velocity Profiles ◽  
Free Shear Layer ◽  
Layer Velocity

A numerical investigation into the effects of compressibility and total enthalpy difference on the development of a laminar free shear layer

1971 ◽  
Vol 50 (4) ◽  
pp. 785-799 ◽  
Author(s):  
Peter W. Carpenter
Keyword(s):  
Boundary Layer ◽  
Shear Layer ◽  
Free Stream ◽  
Equations Of Motion ◽  
Initial Boundary ◽  
Free Shear Layer ◽  
Total Enthalpy ◽  
Enthalpy Difference ◽  
Coefficient Of Viscosity ◽  
Boundary Layer Profile

A method is presented for integrating numerically the equations of motion for a compressible free shear layer developing from a boundary-layer profile of arbitrary shape. Sutherland's law is used to determine the coefficient of viscosity and the Prandtl number is taken as 0·72. Calculated results are reported for free-stream Mach numbers ranging from 0 to 10 and for stagnation-enthalpy ratios ranging from 0 to 5·0. The effects of varying the initial boundary-layer profile and of a discontinuity in temperature at the origin are also studied. The results include graphs showing the development of dividing-streamline velocity, of local Nusselt number, and of dividing-streamline location.

Experimental Study on the Receptivity of Shear Layer Separating at a Rear-Edge of Boundary-Layer Plate

2007 ◽  
Author(s):  
Masahito Asai ◽  
Takeshi Imai
Keyword(s):  
Boundary Layer ◽  
Shear Layer ◽  
Shear Instability ◽  
Instability Mode ◽  
Free Shear Layer ◽  
Frequency Range ◽  
Acoustic Disturbances ◽  
Rear Edge ◽  
Separated Shear Layer ◽  
Vorticity Fluctuation

Receptivity of the free shear layer developing from a 90-degrees rear-edge of boundary-layer plate to acoustic disturbances is examined experimentally to clarify the dependency of the receptivity coefficient on the rear-edge curvature. The results show that for finite rear-edge curvatures, the receptivity coefficient decreases with increasing the disturbance frequency while it is almost independent of the frequency for the sharp rear-edge over the frequency range examined. The decrease in the receptivity coefficient for the rounded rear-edge is attributed to the fact that the sound-induced Stokes layer which is the vorticity fluctuation developing into the free-shear instability mode is shed into the off-centerline of the separated shear layer.

Vortex pairing in a circular jet under controlled excitation. Part 1. General jet response

1980 ◽  
Vol 101 (3) ◽  
pp. 449-491 ◽  
Author(s):  
K. B. M. Q. Zaman ◽  
A. K. M. F. Hussain
Keyword(s):  
Boundary Layer ◽  
Shear Layer ◽  
Strouhal Number ◽  
Reynolds Stress ◽  
Initial Boundary ◽  
Vortex Rings ◽  
Fluctuation Intensity ◽  
Vortex Pairing ◽  
Time Average ◽  
Stable Vortex

Hot-wire and flow-visualization studies have been carried out in three air jets subjected to pure-tone acoustic excitation, and the instability, vortex roll-up and transition as well as jet response to the controlled excitation have been investigated. The centreline fluctuation intensity can be enhanced by inducing stable vortex pairing to a level much higher than even that at the ‘preferred mode’, but can also be suppressed below the unexcited level under certain conditions of excitation. The conditions most favourable to vortex pairing were determined as a function of the excitation Strouhal number, the Reynolds number (ReD), and the initial shear-layer state, i.e. laminar or turbulent. It is shown that the rolled-up vortex rings undergo pairing under two distinct conditions of excitation: ‘the shear layer mode’ when the Strouhal number based on the initial shear-layer momentum thickness (Stθ) is about 0·012, and ‘the jet column mode’ when the Strouhal number based on the jet diameter (StD) is about 0·85. The former involves pairing of the near-exit thin vortex rings when the initial boundary layer is laminar, irrespective of the value of StD. The latter involves pairing of the thick vortex rings at x/D ≅ 1·75, irrespective of Stθ or whether the initial boundary layer is laminar or turbulent. For laminar exit boundary layer, pairing is found to be stable, i.e., occurring regularly in space and time, for ReD < 5 × 104, but becomes intermittent with increasing ReD or fluctuation intensity in the initial boundary layer.The trajectories of the vortex centres and their convection velocities during a pairing event have been recorded through phase-locked measurements. In the presence of stable vortex pairing, the time average profiles of fluctuation intensities and Reynolds stress show noticeable deviations from those in the unexcited jet. The vortex pairing phenomenon produce considerably larger excursions of the $\widetilde{uv}(t)$ signal than the time-average Reynolds stress reveals, suggesting that only certain phases of the pairing process may be important in entrainment, and production of Reynolds stress and jet noise.

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