Investigation of Formation and Development of Stationary and Secondary Disturbances in the Favourable Pressure Gradient Area on the Swept Wing

2013 ◽  
Vol 8 (2) ◽  
pp. 55-69
Author(s):  
Stepan Tolkachev ◽  
Vasily Gorev ◽  
Viktor Kozlov

In this work the combined technique of liquid-crystal thermography and thermoanemometry measurements is used to trace the stationary disturbance development from the moment of formation to the nonlinear stage transition. It has been shown that the pair of stationary vortices are formed after the cylindrical roughness element. These vortices modify a boundary layer and destabilize it. There is the area of maximal receptivity to the roughness location, which in the experiment was distant from the attachment line. If the stationary disturbance has enough magnitude in its core the secondary disturbances excite and lead to the laminar-turbulent transition. Secondary disturbances are sensitive to the acoustics and achieve the magnitude in hundred times higher than for the natural case

2012 ◽  
Vol 7 (2) ◽  
pp. 66-79
Author(s):  
Stepan Tolkachev ◽  
Vasily Gorev ◽  
Galina Zharkova ◽  
Valentina Kovrizhina

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


2014 ◽  
Vol 9 (4) ◽  
pp. 65-73
Author(s):  
Stepan Tolkachev ◽  
Valeria Kaprilevskaya ◽  
Viktor Kozlov

In the article using a liquid crystal thermography investigated the development of stationary and secondary disturbances, which were excited by cylindrical and two-dimensional roughness elements. It was shown, that two-dimensional roughness element has a destabilizing effect on disturbances, induced by cylindrical roughness element. Also the twodimensional roughness element is able to excite the stationary structures, and then the secondary disturbances the frequency interval of which is lower than in the case of stationary vortices excitation by cylindrical roughness element


Author(s):  
Alexander Kosinov ◽  
Nikolai Semionov ◽  
Yury Yermolaev ◽  
Boris Smorodsky ◽  
Gleb Kolosov ◽  
...  

The paper is devoted to an experimental and theoretical study of effect of moderate angle-of-attack variation on disturbances evolution and laminar-turbulent transition in a supersonic boundary layer on swept wing at Mach 2. Monotonous growth of the transition Reynolds numbers with angle of attack increasing from −2° to 2.7° is confirmed. For the same conditions, calculations based on linear stability theory are performed. The experimental and computational results show a favourable comparison.


Author(s):  
Stepan Tolkachev ◽  
Victor Kozlov ◽  
Valeriya Kaprilevskaya

In this article, the results of research about stationary and secondary disturbances development behind the localized and two-dimensional roughness elements are presented. It is shown that the two-dimensional roughness element has a destabilizing effect on the disturbances induced by the three-dimensional roughness element lying upstream. In this case, the two-dimensional roughness element causes the appearance of stationary structures, and then secondary perturbations, whose frequency range lies lower than in the case of the stationary vortices excited by a three-dimensional roughness element.


2018 ◽  
Vol 844 ◽  
pp. 36-60 ◽  
Author(s):  
Nima Shahriari ◽  
Matthias R. Kollert ◽  
Ardeshir Hanifi

Application of ring-type plasma actuators for control of laminar–turbulent transition in a swept-wing boundary layer is investigated thorough direct numerical simulations. These actuators induce a wall-normal jet in the boundary layer and can act as virtual roughness elements. The flow configuration resembles experiments by Kim et al. (2016 Technical Report. BUTERFLI Project TR D3.19, http://eprints.nottingham.ac.uk/id/eprint/46529). The actuators are modelled by the volume forces computed from the experimentally measured induced velocity field at the quiescent air condition. Stationary and travelling cross-flow vortices are triggered in the simulations by means of surface roughness and random unsteady perturbations. Interaction of vortices generated by actuators with these perturbations is investigated in detail. It is found that, for successful transition control, the power of the actuators should be increased to generate jet velocities that are one order of magnitude higher than those used in the experiments by Kim et al. (2016) mentioned above.


1967 ◽  
Vol 18 (2) ◽  
pp. 150-164 ◽  
Author(s):  
N. A. Cumpsty ◽  
M. R. Head

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.


1997 ◽  
Author(s):  
Xiaoli Huai ◽  
Ugo Piomelli ◽  
Ronald Joslin ◽  
Xiaoli Huai ◽  
Ugo Piomelli ◽  
...  

2018 ◽  
pp. 4-28
Author(s):  
Анатолій Михайлович Павлюченко ◽  
Олександр Миколайович Шийко

The complex method of calculation of aerodynamic resistance of friction and heating on the surface of flight axisymmetric bodies of rotation like a jet uncontrollable shell is developed. The method allows to carry out calculations from the moment of start to landing in limits to-, a trance- and supersonic speeds of flight. Range of speeds corresponds to М∞ ≤ 3,0 Mach numbers. When calculating the phenomena of a non-isothermicity, compressibility, laminar-turbulenttransition and a relaminarization which occur on streamline surfaces when flying on a trajectory are considered. The method is based on use of the asymptotic theory ofa wall turbulent boundary layer ofS.S. Kutateladze and A. І. Leontyeva in combination with results of the linearized theory of flow of bodies of rotation, the theory of turbulent spots of Emmons of a transitionalboundary layer and data on Reynolds numbers of the beginning of laminar-turbulenttransition received by results of flight experiments. On the basis of the carried-out calculations of parameters of a stream on a streamline surface of a shell when flying on a trajectory from the moment of start to landing in limits to-, a trance- and supersonic speeds of flight with use of the boundary numbers of laminar-turbulent transitionreceived in flight experiments it is established that flow of a considerable part of a surface of a shell happens in the conditions of laminar-turbulent transition and a relaminarization which occupy an essential part of the general time of flight. Existence of a reverse of laminar-turbulent transition is established by a settlement way. The analysis of values of temperature on a surface of a head part of a rocket when flying on a settlement trajectory has shown that for rather short period there is an aerodynamic heating of a surface which significantly influences the aerodynamic resistance of friction by a non-isothermicity in a wall boundary layer. The conclusion is drawn that the linearized theory of calculations of flow of rather thin bodies of rotation can be used for calculation of parameters on external border of boundary layer of axisymmetric bodies of rotation like a jet uncontrollable shell in limits to-, a trance- and supersonic speeds of flight for the purpose of account longitudinal to pressure gradient when calculating friction and heating. Use of the linearized theory of flow for calculation of parameters on external border of boundary layer in limits to-, a trance- and supersonic speeds of flight allows to create a "fast" algorithm of calculation of resistance of friction and heating taking into account a longitudinal gradient of pressure existing on the streamline surfaces of axisymmetric bodies of rotation. Numerical results of calculations of parameters of a nonviscous current on external border of boundary layerfor the linearized theory, coefficient of a intermittency, temperature of heating of a surface of a shell and resistance of friction from the start moment before landing are given


2015 ◽  
Vol 775 ◽  
Author(s):  
Gianluca Meneghello ◽  
Peter J. Schmid ◽  
Patrick Huerre

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.


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