Experimental Studies of the Localized Disturbances and their Secondary High-Frequency Instability in the Flat Plate, Unswept and Swept Wing Boundary Layer (Review)

2014 ◽  
Vol 9 (4) ◽  
pp. 39-64
Author(s):  
Viktor Kozlov ◽  
Genrich Grek ◽  
Yuriy Litvinenko ◽  
Stepan Tolkachev ◽  
Valeriy Chernoray
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
High Frequency ◽  
Flow Instability ◽  
Experimental Studies ◽  
Frequency Instability ◽  
Swept Wing ◽  
Streaky Structure ◽  
Streaky Structures ◽  
Nonlinear Stage

Results of experimental studies of the streaky structures instability at nonlinear stage of this process in the shear flows are shown in this work. Flow patterns of the streaky structures with secondary high-frequency disturbances generated on them during its spatial evolution are discussed. Different scenarios of the coherent vortical structures occurrence and downstream evolution in the flat plate, unswept and swept wing boundary layer are considered. Features of the sinusoidal and varicose instability of the longitudinal stationary streaky structure at nonlinear stage of its downstream development are shown. To these features concern: modulation of streaky structure in transverse and streamwise direction by frequency of secondary disturbances, occurrence of new streaky structures downstream and occurrence and development of the nonstationary localized vortices such as Λ-structures in both cases. Development of a nonlinear stage of flow instability is considered both in the region of the adverse and zero pressure gradient

Skin friction and surface temperature of an insulated flat plate fixed in a fluctuating stream

1971 ◽  
Vol 46 (1) ◽  
pp. 165-175 ◽  
Author(s):  
Hiroshi Ishigaki
Keyword(s):  
Boundary Layer ◽  
Surface Temperature ◽  
Flat Plate ◽  
Skin Friction ◽  
High Frequency ◽  
Energy Equation ◽  
Oscillation Amplitude ◽  
Flow Oscillation ◽  
Velocity Amplitude ◽  
The Mean

The time-mean skin friction of the laminar boundary layer on a flat plate which is fixed at zero incidence in a fluctuating stream is investigated analytically. Flow oscillation amplitude outside the boundary layer is assumed constant along the surface. First, the small velocity-amplitude case is treated, and approximate formulae are obtained in the extreme cases when the frequency is low and high. Next, the finite velocity-amplitude case is treated under the condition of high frequency, and it is found that the formula obtained for the small-amplitude and high-frequency case is also valid. These results show that the increase of the mean skin friction reduces with frequency and is ultimately inversely proportional to the square of frequency.The corresponding energy equation is also studied simultaneously under the condition of zero heat transfer between the fluid and the surface. It is confirmed that the time-mean surface temperature increases with frequency and tends to be proportional to the square root of frequency. Moreover, it is shown that the timemean recovery factor can be several times as large as that without flow oscillation.

Experimental investigation of high-frequency secondary disturbances in a swept-wing boundary layer

1995 ◽  
Vol 36 (3) ◽  
pp. 385-393 ◽  
Author(s):  
A. V. Boiko ◽  
V. V. Kozlov ◽  
V. V. Syzrantsev ◽  
V. A. Shcherbakov
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
High Frequency ◽  
Swept Wing

Receptivity and sensitivity of the leading-edge boundary layer of a swept wing

2015 ◽  
Vol 775 ◽  
Author(s):  
Gianluca Meneghello ◽  
Peter J. Schmid ◽  
Patrick Huerre
Keyword(s):  
Boundary Layer ◽  
Flow Instability ◽  
Cross Flow ◽  
Leading Edge ◽  
Open Loop ◽  
Base Flow ◽  
Local Instability ◽  
Swept Wing ◽  
Global Mode ◽  
Attachment Line

A global stability analysis of the boundary layer in the leading edge of a swept wing is performed in the incompressible flow regime. It is demonstrated that the global eigenfunctions display the features characterizing the local instability of the attachment line, as in swept Hiemenz flow, and those of local cross-flow instabilities further downstream along the wing. A continuous connection along the chordwise direction is established between the two local eigenfunctions. An adjoint-based receptivity analysis reveals that the global eigenfunction is most responsive to forcing applied in the immediate vicinity of the attachment line. Furthermore, a sensitivity analysis identifies the wavemaker at a location that is also very close to the attachment line where the corresponding local instability analysis holds: the local cross-flow instability further along the wing is merely fed by its attachment-line counterpart. As a consequence, global mode calculations for the entire leading-edge region only need to include attachment-line structures. The result additionally implies that effective open-loop control strategies should focus on base-flow modifications in the region where the local attachment-line instability prevails.

Experimental Studies on Wake-Induced Transition of Turbulent Boundary Layers

2012 ◽  
Author(s):  
Keiji Takeuchi ◽  
Susumu Fujimoto ◽  
Eitaro Koyabu ◽  
Tetsuhiro Tsukiji
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Boundary Layers ◽  
Turbulence Intensity ◽  
Intensity Distribution ◽  
Experimental Studies ◽  
Turbulent Boundary Layers ◽  
Bypass Transition ◽  
Pressure Gradients ◽  
Hot Wire

Wake-induced bypass transition of boundary layers on a flat plate subjected to favorable and adverse pressure gradients was investigated. Detailed boundary layer measurements were conducted using two hot-wire probes. A spoked-wheel-type wake generator was used to create periodic wakes in front of the flat plate. The main focus of this study was to reveal the effect of the Strouhal number, which changed by using different numbers of wake-generating bars, on the turbulence intensity distribution and the transition onset position of the boundary layer on the flat plate using two hot-wire probes.

The effect of oscillation on flat plate heat transfer

1971 ◽  
Vol 47 (3) ◽  
pp. 537-546 ◽  
Author(s):  
Hiroshi Ishigaki
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Flat Plate ◽  
Viscous Dissipation ◽  
High Frequency ◽  
Small Amplitude ◽  
Oscillation Amplitude ◽  
Flow Oscillation ◽  
Velocity Amplitude ◽  
Dissipation Effect

The time-mean heat transfer of the incompressible laminar boundary layer on a flat plate under the influence of oscillation is studied analytically. Flow oscillation amplitude outside the boundary layer is assumed constant along the surface and the viscous dissipation effect is considered. First, the small velocity–amplitude case is treated and the approximate formulae are obtained in the extreme cases when the frequency is low and high. Next, the finite velocity–amplitude case is treated under the condition of high frequency and it is found that the formulae obtained for the small amplitude and high frequency case are also valid. These results show that, when the oscillation is of high frequency, the time-mean heat flux to the wall can be several times as large as that without oscillation. This is due wholly to the viscous dissipation effect combined with oscillation.

scholarly journals Experimental Study of the Influence of Unit Reynolds Number on the Laminar-Turbulent Transition on the Model Swept Wing with a Subsonic Leading Edge at M = 2

2021 ◽  
Vol 16 (1) ◽  
pp. 44-52
Author(s):  
Vasilii L. Kocharin ◽  
Nikolai V. Semionov ◽  
Alexander D. Kosinov ◽  
Aleksey A. Yatskikh ◽  
Sofia A. Shipul ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Experimental Studies ◽  
Leading Edge ◽  
Supersonic Boundary Layer ◽  
Swept Wing ◽  
Unit Reynolds Number ◽  
Flow Parameters ◽  
Turbulent Transition ◽  
Laminar Turbulent Transition

Experimental studies of the influence of unit Reynolds number on the laminar-turbulent transition in a supersonic boundary layer of a swept wing with a subsonic leading edge at Mach number 2 are performed. The experiments were performed on a model of a swept wing with a swept angle of the leading edge of 72 degrees and with a 3% profile with a variable chord length in span. The hot-wire measurements showed that a laminar-turbulent transition in a supersonic boundary layer of a swept wing with a subsonic leading edge occurs earlier (~25-30%) than on a model with a supersonic leading edge with the same oncoming flow parameters. It is shown that a change unit Reynolds number insignificant influence the laminar-turbulent transition in the boundary layer of a swept wing with a subsonic leading edge.

scholarly journals Transition in an infinite swept-wing boundary layer subject to surface roughness and free-stream turbulence

2021 ◽  
Vol 931 ◽  
Author(s):  
Luca De Vincentiis ◽  
Dan S. Henningson ◽  
Ardeshir Hanifi
Keyword(s):  
Boundary Layer ◽  
Free Stream ◽  
Flow Instability ◽  
Transition To Turbulence ◽  
Computational Domain ◽  
Swept Wing ◽  
Free Stream Turbulence ◽  
Roughness Elements ◽  
Layer Flow ◽  
Institute Of Technology

The instability of an incompressible boundary-layer flow over an infinite swept wing in the presence of disc-type roughness elements and free-stream turbulence (FST) has been investigated by means of direct numerical simulations. Our study corresponds to the experiments by Örlü et al. (Tech. Rep., KTH Royal Institute of Technology, 2021, http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-291874). Here, different dimensions of the roughness elements and levels of FST have been considered. The aim of the present work is to investigate the experimentally observed sensitivity of the transition to the FST intensity. In the absence of FST, flow behind the roughness elements with a height above a certain value immediately undergoes transition to turbulence. Impulse–response analyses of the steady flow have been performed to identify the mechanism behind the observed flow instability. For subcritical roughness, the generated wave packet experiences a weak transient growth behind the roughness and then its amplitude decays as it is advected out of the computational domain. In the supercritical case, in which the flow transitions to turbulence, flow as expected exhibits an absolute instability. The presence of FST is found to have a significant impact on the transition behind the roughness, in particular in the case of a subcritical roughness height. For a height corresponding to a roughness Reynolds number $Re_{hh}=461$ , in the absence of FST the flow reaches a steady laminar state, while a very low FST intensity of $Tu =0.03\,\%$ causes the appearance of turbulence spots in the wake of the roughness. These randomly generated spots are advected out of the computational domain. For a higher FST level of $Tu=0.3\,\%$ , a turbulent wake is clearly visible behind the element, similar to that for the globally unstable case. The presented results confirm the experimental observations and explain the mechanisms behind the observed laminar–turbulent transition and its sensitivity to FST.

G0500-3-4 Experimental Studies on Boundary Layer Bypass Transition on a Flat-Plate Subjected to Incident Wakes

2010 ◽  
Vol 2010.2 (0) ◽  
pp. 279-280
Author(s):  
Eitaro KOYABU ◽  
Satoshi IMADA ◽  
Susumu FUJIMOTO ◽  
Tetsuhiro TSUKIJI
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Experimental Studies ◽  
Bypass Transition
Sign in / Sign up

Export Citation Format

Share Document