scholarly journals Correlation for Length of Impinging Shock-Induced Large Separation Bubble at Hypersonic Speed

AIAA Journal ◽  
2015 ◽  
Vol 53 (9) ◽  
pp. 2771-2776 ◽  
Author(s):  
R. Sriram ◽  
G. Jagadeesh
Keyword(s):  
Separation Bubble ◽  
Hypersonic Speed ◽  
Large Separation

scholarly journals Microvortex generator for scramjet inlet application

2019 ◽  
Author(s):  
A.C. Idris ◽  
M.R. Saad ◽  
K. Kontis
Keyword(s):  
Boundary Layer ◽  
Peak Pressure ◽  
Separation Bubble ◽  
Vortex Pairs ◽  
Large Separation ◽  
Flow Phenomena ◽  
Global Pressure ◽  
Measurement Approach

Global measurement approach in characterizing a generic scramjet inlet has enabled the investigation of various flow phenomena typically occurred on an inlet to be investigated further. This paper examines the effectiveness of microvortex generator (MVG) array in suppressing boundary layer separations on such an inlet. Global measurement of pressure and temperature were employed to visualize vortex pairs emanating from the MVG. The global pressure map showed the benefit of lower reattachment peak pressure that usually accompanies the large separation bubble at a scramjet inlet throat.

On the length scales of hypersonic shock-induced large separation bubbles near leading edges

2016 ◽  
Vol 806 ◽  
pp. 304-355 ◽  
Author(s):  
R. Sriram ◽  
L. Srinath ◽  
Manoj Kumar K. Devaraj ◽  
G. Jagadeesh
Keyword(s):  
Boundary Layer ◽  
Mach Number ◽  
Separation Bubble ◽  
Scaling Law ◽  
Leading Edge ◽  
Large Separation ◽  
Hypersonic Shock ◽  
Shock Impingement ◽  
Leading Edges ◽  
Sharp Leading Edge

The interaction of a hypersonic boundary layer on a flat plate with an impinging shock – an order of magnitude stronger than that required for incipient separation of the boundary layer – near sharp and blunt leading edges (with different bluntness radii from 2 to 6 mm) is investigated experimentally, complemented by numerical computations. The resultant separation bubble is of length comparable to the distance of shock impingement from the leading edge, rather than the boundary layer thickness at separation; it is termed large separation bubble. Experiments are performed in the IISc hypersonic shock tunnel HST-2 at nominal Mach numbers 5.88 and 8.54, with total enthalpies 1.26 and $1.85~\text{MJ}~\text{kg}^{-1}$ respectively. Schlieren flow visualization using a high-speed camera and surface pressure measurements using fast response sensors are the diagnostics. For the sharp leading edge case, the separation length was found to follow an inviscid scaling law according to which the scaled separation length $(L_{sep}/x_{r})M_{er}^{3}$ is found to be linearly related to the reattachment pressure ratio $p_{r}/p_{er}$; where $L_{sep}$ is the measured separation length, $x_{r}$ the distance of reattachment from the leading edge, $M$ the Mach number, $p$ the static pressure and the subscripts $r$ and $e$ denote the conditions at the reattachment location and at the edge of the boundary layer at the shock impingement location respectively. However, for all the blunt leading edges $(L_{sep}/x_{r})M_{er}^{3}$ was found to be a constant irrespective of Mach number and much smaller than the sharp leading edge cases. The possible contributions of viscous and non-viscous mechanisms towards the observed phenomena are explored.

Active Forcing of a Pressure-Induced Turbulent Separation Bubble

2020 ◽  
Author(s):  
Abdelouahab T. Mohammed-Taifour ◽  
Arnaud Le Floc'h ◽  
Julien Weiss
Keyword(s):  
Separation Bubble ◽  
Turbulent Separation

Characteristics of a separated flow past a semicircular leading-edge airfoil model under different imposed pressure gradient

2021 ◽  
pp. 095441002110212
Author(s):  
K Anand ◽  
KT Ganesh
Keyword(s):  
Boundary Layer ◽  
Particle Image Velocimetry ◽  
Pressure Gradient ◽  
Particle Image ◽  
Separation Bubble ◽  
Separated Flow ◽  
Leading Edge ◽  
Field Measurements ◽  
Bench Mark ◽  
Image Velocimetry

The effect of pressure gradient on a separated boundary layer past the leading edge of an airfoil model is studied experimentally using electronically scanned pressure (ESP) and particle image velocimetry (PIV) for a Reynolds number ( Re) of 25,000, based on leading-edge diameter ( D). The features of the boundary layer in the region of separation and its development past the reattachment location are examined for three cases of β (−30°, 0°, and +30°). The bubble parameters such as the onset of separation and transition and the reattachment location are identified from the averaged data obtained from pressure and velocity measurements. Surface pressure measurements obtained from ESP show a surge in wall static pressure for β = −30° (flap deflected up), while it goes down for β = +30° (flap deflected down) compared to the fundamental case, β = 0°. Particle image velocimetry results show that the roll up of the shear layer past the onset of separation is early for β = +30°, owing to higher amplification of background disturbances compared to β = 0° and −30°. Downstream to transition location, the instantaneous field measurements reveal a stretched, disoriented, and at instances bigger vortices for β = +30°, whereas a regular, periodically shed vortices, keeping their identity past the reattachment location, is observed for β = 0° and −30°. Above all, this study presents a new insight on the features of a separation bubble receiving a disturbance from the downstream end of the model, and these results may serve as a bench mark for future studies over an airfoil under similar environment.

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