Characteristics of the Turbulent Boundary Layer on a Glass Surface of a Channel behind a Shock Wave
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acteristics of the Turbulent Boundary Layer on a Glass Surface of a Channel behind a Shock Wave I. A. Doroshchenkoa, I. A. Znamenskayaa, T. A. Kuli-zadea, and D. I. Tatarenkovaa,* a
Moscow State University, Faculty of Physics, Moscow, 119991 Russia *е-mail: [email protected]
Received March 1, 2020; revised March 12, 2020; accepted March 12, 2020
Abstract—The effect of laminar and turbulent boundary layers on the localization of pulsed discharge glow in gas in rest and in flow in a gasdynamic channel is studied. It is found that the glow of a discharge localized into the separation zone on a glass surface is of the form of regular structures capturing the structure of turbulent inhomogeneities in the boundary layer. The flow visualization was performed using a pulsed space discharge with UV preionization realized in a working chamber of rectangular section. Keywords: pulsed space discharge, boundary layer, laminar-turbulent transition, supersonic flow, high-speed filming DOI: 10.1134/S0015462820050043
In recent decades the possibility of controlling gas flows by means of gas discharges has been actively investigated. Various studies have shown that an effective action on a high-velocity gas flow needs in a pulsed or pulsed-periodic power source. It is pulsed discharges, such as an optical discharge or high-current nanosecond discharges, that are best suited for such a power source. The duration of the gas heating realized by this discharge is much less than the characteristic times of the gasdynamic flow. The plasma instabilities have no time to develop during the breakthrough time. The discharge action on the flow is chiefly determined by the energy contribution and its homogeneity [1], the discharge region configuration, and the original flow parameters. One of the most important problems of the present-day aerodynamics is the control of laminar-turbulent transition in boundary layers [2, 3]. Usually, this process is described by theory of hydrodynamic stability [4, 5]. Two main mechanisms of transition to turbulence may be noted; they correspond to small and high turbulence levels in the freestream. At low turbulence level the transition process can be subdivided into the following stages: (1) small amplitude perturbations (Tollmien—Schlichting waves); (2) threedimensional development of instability waves with finite amplitudes (Λ structures); and (3) formation, development, and interaction of turbulent spots. At high freestream turbulence levels the transition mechanism is as follows: (1) stage of the streaky structure development; (2) nonlinear development and initiation of turbulent spots; and (3) development and interaction of turbulent spots [4]. In supersonic flows the location of the laminar-turbulent transition region is usually determined by means of recording the signals from thermal or pressure transducers on the surface in a flow [6]. The boundary flow visualization using the shadow method is mainly applicable to two-dimensional flows [7]. One of the effective methods of visualizing the st
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