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.

Stabilization of a swept-wing boundary layer by distributed roughness elements

2013 ◽  
Vol 718 ◽  
Author(s):  
Seyed M. Hosseini ◽  
David Tempelmann ◽  
Ardeshir Hanifi ◽  
Dan S. Henningson
Keyword(s):  
Boundary Layer ◽  
Control Method ◽  
Cross Flow ◽  
Leading Edge ◽  
Base Flow ◽  
Flow Mode ◽  
Swept Wing ◽  
Free Stream Turbulence ◽  
Flow Disturbances ◽  
Roughness Elements

AbstractThe stabilization of a swept-wing boundary layer by distributed surface roughness elements is studied by performing direct numerical simulations. The configuration resembles experiments studied by Saric and coworkers at Arizona State University, who employed this control method in order to delay transition. An array of cylindrical roughness elements are placed near the leading edge to excite subcritical cross-flow modes. Subcritical refers to the modes that are not critical with respect to transition. Their amplification to nonlinear amplitudes modifies the base flow such that the most unstable cross-flow mode and secondary instabilities are damped, resulting in downstream shift of the transition location. The experiments by Saric and coworkers were performed at low levels of free stream turbulence, and the boundary layer was therefore dominated by stationary cross-flow disturbances. Here, we consider a more complex disturbance field, which comprises both steady and unsteady instabilities of similar amplitudes. It is demonstrated that the control is robust with respect to complex disturbance fields as transition is shifted from 45 to 65 % chord.

Experimental control of swept-wing transition through base-flow modification by plasma actuators

2018 ◽  
Vol 844 ◽  
Author(s):  
Srikar Yadala ◽  
Marc T. Hehner ◽  
Jacopo Serpieri ◽  
Nicolas Benard ◽  
Philipp C. Dörr ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Cross Flow ◽  
Leading Edge ◽  
Base Flow ◽  
Plasma Actuators ◽  
Simplified Model ◽  
Swept Wing ◽  
Flow Component ◽  
Flow Modification ◽  
Barrier Discharge Plasma

Control of laminar-to-turbulent transition on a swept-wing is achieved by base-flow modification in an experimental framework, up to a chord Reynolds number of 2.5 million. This technique is based on the control strategy used in the numerical simulation by Dörr & Kloker (J. Phys. D: Appl. Phys., vol. 48, 2015b, 285205). A spanwise uniform body force is introduced using dielectric barrier discharge plasma actuators, to either force against or along the local cross-flow component of the boundary layer. The effect of forcing on the stability of the boundary layer is analysed using a simplified model proposed by Serpieri et al. (J. Fluid Mech., vol. 833, 2017, pp. 164–205). A minimal thickness plasma actuator is fabricated using spray-on techniques and positioned near the leading edge of the swept-wing, while infrared thermography is used to detect and quantify transition location. Results from both the simplified model and experiment indicate that forcing along the local cross-flow component promotes transition while forcing against successfully delays transition. This is the first experimental demonstration of swept-wing transition delay via base-flow modification using plasma actuators.

The Calculation of Three-Dimensional Turbulent Boundary Layers: Part II: Attachment-Line Flow on an Infinite Swept Wing

1967 ◽  
Vol 18 (2) ◽  
pp. 150-164 ◽  
Author(s):  
N. A. Cumpsty ◽  
M. R. Head
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Boundary Layer Flow ◽  
Three Dimensional ◽  
Cross Flow ◽  
Swept Wing ◽  
Turbulent Boundary Layer Flow ◽  
Layer Flow ◽  
Momentum Integral ◽  
Attachment Line

SummaryAn earlier paper described a method of calculating the turbulent boundary layer flow over the rear of an infinite swept wing. It made use of an entrainment equation and momentum integral equations in streamwise and cross-flow directions, together with several auxiliary assumptions. Here the method is adapted to the calculation of the turbulent boundary layer flow along the attachment line of an infinite swept wing. In this case the cross-flow momentum integral equation reduces to the identity 0 = 0 and must be replaced by its differentiated form. Two alternative approaches are also adopted and give very similar results, in good agreement with the limited experimental data available. It is found that results can be expressed as functions of a single parameter C*, which is evidently the criterion of similarity for attachment-line flows.

Experimental Techniques of the Study of the Vortex Disturbances Structure Caused by Point Injection on the Swept Wing Leading Edge

2012 ◽  
Vol 7 (2) ◽  
pp. 66-79
Author(s):  
Stepan Tolkachev ◽  
Vasily Gorev ◽  
Galina Zharkova ◽  
Valentina Kovrizhina
Keyword(s):  
Boundary Layer ◽  
Liquid Crystal ◽  
Leading Edge ◽  
Swept Wing ◽  
Liquid Crystal Thermography ◽  
Point Injection ◽  
Stationary Vortex ◽  
To Receive ◽  
Attachment Line ◽  
Good Agreement

The article contains the results of thermoanemometry on the curvilinear surface and liquid crystal thermography techniques for the investigation of the flow stability on the swept wing leading edge. The numeric results of the velocity disturbance distribution in the boundary layer near the attachment line were received with a help of the thermoanemometry technique. It was found out, that the boundary layer become less stable, when a stationary vortex modifies the flow. The liquid crystal thermography technique allowed to expand the workspace for investigations up to 70 from the attachment line, to receive the visualization pictures of disturbed flow for several regimes of blowing, to reveal an influence of the blow velocity on dimensions and trajectory of stationary disturbances, which were induced by injection. The results of visualizations are in a good agreement with thermoanemometry results

The long-time behaviour of incompressible swept-wing boundary layers subject to impulsive forcing

1998 ◽  
Vol 355 ◽  
pp. 359-381 ◽  
Author(s):  
M. J. TAYLOR ◽  
N. PEAKE
Keyword(s):  
Boundary Layer ◽  
Flow Direction ◽  
Three Dimensional ◽  
Cross Flow ◽  
Leading Edge ◽  
Rotating Disk ◽  
Linear Stability Theory ◽  
Swept Wing ◽  
Long Time ◽  
Layer Flow

The long-time limit of the response of incompressible three-dimensional boundary layer flows on infinite swept wedges and infinite swept wings to impulsive forcing is examined using causal linear stability theory. Following the discovery by Lingwood (1995) of the presence of absolute instabilities caused by pinch points occurring in the radial direction in the boundary layer flow of a rotating disk, we search for pinch points in the cross flow direction for both the model Falkner–Skan–Cooke profile of a swept wedge and for a genuine swept-wing configuration. It is shown in both cases that, within a particular range of the parameter space, the boundary layer does indeed support pinch points in the wavenumber plane corresponding to the crossflow direction. These crossflow-induced pinch points do not constitute an absolute instability, as there is no simultaneous pinch occurring in the streamwise wavenumber plane, but nevertheless we show here how they can be used to find the maximum local growth rate contained in a wavepacket travelling in any given direction. Lingwood (1997) also found pinch points in the chordwise wavenumber plane in the boundary layer of the leading-edge region of a swept wing (i.e. at very high flow angles). The results presented in this paper, however, demonstrate the presence of pinch points for a much larger range of flow angles and pressure gradients than was found by Lingwood, and indeed describe the flow over a much greater, and practically significant, portion of the wing.

scholarly journals Quantitative study of localized mechanisms of excitation of cross-flow instability modes in a swept-wing boundary layer

2018 ◽  
Vol 1129 ◽  
pp. 012008
Author(s):  
V I Borodulin ◽  
A V Ivanov ◽  
Y S Kachanov ◽  
D A Mischenko ◽  
R Örlü ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Quantitative Study ◽  
Flow Instability ◽  
Cross Flow ◽  
Swept Wing ◽  
Instability Modes
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