Detection of the laminar-turbulent transition line in a three-dimensional boundary layer by observing of evolving thermograms

2019 ◽  
Author(s):  
V. I. Borodulin ◽  
Y. S. Kachanov
Keyword(s):  
Boundary Layer ◽  
Three Dimensional ◽  
Transition Line ◽  
Turbulent Transition ◽  
Dimensional Boundary ◽  
Laminar Turbulent Transition

Review: Laminar-to-Turbulent Transition of Three-Dimensional Boundary Layers on Rotating Bodies

1994 ◽  
Vol 116 (2) ◽  
pp. 200-211 ◽  
Author(s):  
Ryoji Kobayashi
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Three Dimensional ◽  
Speed Ratio ◽  
Stream Velocity ◽  
Turbulent Transition ◽  
Centrifugal Instability ◽  
Crossflow Instability ◽  
Dimensional Boundary ◽  
Axisymmetric Bodies

The laminar-turbulent transition of three-dimensional boundary layers is critically reviewed for some typical axisymmetric bodies rotating in still fluid or in axial flow. The flow structures of the transition regions are visualized. The transition phenomena are driven by the compound of the Tollmien-Schlichting instability, the crossflow instability, and the centrifugal instability. Experimental evidence is provided relating the critical and transition Reynolds numbers, defined in terms of the local velocity and the boundary layer momentum thickness, to the local rotational speed ratio, defined as the ratio of the circumferential speed to the free-stream velocity at the outer edge of the boundary layer, for the rotating disk, the rotating cone, the rotating sphere and other rotating axisymmetric bodies. It is shown that the cross-sectional structure of spiral vortices appearing in the transition regions and the flow pattern of the following secondary instability in the case of the crossflow instability are clearly different than those in the case of the centrifugal instability.

scholarly journals Laminar–turbulent transition induced by a discrete roughness element in a supersonic boundary layer

2013 ◽  
Vol 735 ◽  
pp. 613-646 ◽  
Author(s):  
N. De Tullio ◽  
P. Paredes ◽  
N. D. Sandham ◽  
V. Theofilis
Keyword(s):  
Boundary Layer ◽  
Shear Layer ◽  
Roughness Element ◽  
Three Dimensional ◽  
Supersonic Boundary Layer ◽  
Low Velocity ◽  
Adiabatic Wall ◽  
Turbulent Transition ◽  
Displacement Thickness ◽  
Laminar Turbulent Transition

AbstractThe linear instability and breakdown to turbulence induced by an isolated roughness element in a boundary layer at Mach $2. 5$, over an isothermal flat plate with laminar adiabatic wall temperature, have been analysed by means of direct numerical simulations, aided by spatial BiGlobal and three-dimensional parabolized (PSE-3D) stability analyses. It is important to understand transition in this flow regime since the process can be slower than in incompressible flow and is crucial to prediction of local heat loads on next-generation flight vehicles. The results show that the roughness element, with a height of the order of the boundary layer displacement thickness, generates a highly unstable wake, which is composed of a low-velocity streak surrounded by a three-dimensional high-shear layer and is able to sustain the rapid growth of a number of instability modes. The most unstable of these modes are associated with varicose or sinuous deformations of the low-velocity streak; they are a consequence of the instability developing in the three-dimensional shear layer as a whole (the varicose mode) or in the lateral shear layers (the sinuous mode). The most unstable wake mode is of the varicose type and grows on average ${\sim }17\hspace{0.167em} \% $ faster than the most unstable sinuous mode and ${\sim }30$ times faster than the most unstable boundary layer mode occurring in the absence of a roughness element. Due to the high growth-rates registered in the presence of the roughness element, an amplification factor of $N= 9$ is reached within ${\sim }50$ roughness heights from the roughness trailing edge. The independently performed Navier–Stokes, spatial BiGlobal and PSE-3D stability results are in excellent agreement with each other, validating the use of simplified theories for roughness-induced transition involving wake instabilities. Following the linear stages of the laminar–turbulent transition process, the roll-up of the three-dimensional shear layer leads to the formation of a wedge of turbulence, which spreads laterally at a rate similar to that observed in the case of compressible turbulent spots for the same Mach number.

scholarly journals Simulation of a laminar-turbulent flow in three-dimensional aerodynamic configurations

2021 ◽  
Vol 2057 (1) ◽  
pp. 012080
Author(s):  
T V Poplavskaya ◽  
A V Boiko ◽  
K V Demyanko ◽  
S V Kirilovskiy ◽  
Y M Nechepurenko
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Turbulent Flow ◽  
Three Dimensional ◽  
Prolate Spheroid ◽  
Turbulent Transition ◽  
Good Agreement ◽  
Laminar Turbulent Transition

Abstract The goal of the paper is to determine the position of the laminar-turbulent transition in the boundary layer of a prolate spheroid using the eN-method with the calibration of threshold N-factors. It is demonstrated that the predicted and experimental data on the laminarturbulent transition are in good agreement.

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