Journal ArticleDOI
Swept-wing boundary-layer transition at various external perturbations: Scenarios, criteria, and problems of prediction
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In this paper, a parametric study of characteristics of laminar-turbulent transition occurred in a model of a crossflow-dominated swept-wing boundary layer in 39 different regimes with low and elevated freestream turbulence levels.Abstract:
This experimental work is devoted to a parametric study of characteristics of the laminar-turbulent transition occurred in a model of a crossflow-dominated swept-wing boundary layer. The experiments are performed in 39 different regimes with low and elevated freestream turbulence levels both in the absence and in the presence of steady freestream vortices of various spanwise scales. The measurements are performed at several values of freestream velocity for two types of distributed surface roughness. Transition scenarios and criteria of turbulence onset are investigated and the problem of transition prediction is examined. It is shown that in all studied cases, the turbulence onset starts with the appearance of local high-frequency secondary instability of the base flow perturbed by primary instability modes. It is found that the 30% level of the threshold zero-to-peak amplitude of combined boundary-layer disturbances (i.e., the steady ones plus unsteady ones) can be used in all studied cases as a simplif...read more
Citations
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Journal ArticleDOI
An alternative method to study cross-flow instabilities based on high order dynamic mode decomposition
TL;DR: In this paper, a novel method for the determination of N-factors in cross-flow transition scenarios is presented, in which a turbulent model is applied downstream from a predetermined point and solves a laminar flow upstream from this point.
Journal ArticleDOI
Experimental and theoretical study of swept-wing boundary-layer instabilities. Unsteady crossflow instability
V. I. Borodulin,Andrey V. Ivanov,Yury S. Kachanov,D. A. Mischenko,Ramis Örlü,Ardeshir Hanifi,Stefan Hein +6 more
TL;DR: In this paper, the linear evolution of unsteady Cross-Flow (CF) and 3D Tollmien-Schlichting (TS) instability modes of 3D boundary layers developing on a swept airfoil section have been carried out.
Journal ArticleDOI
Control of crossflow-vortex-induced transition by unsteady control vortices
Zhengfei Guo,Markus J. Kloker +1 more
TL;DR: In this paper, the fundamental mechanisms of a hitherto unstudied approach to control the crossflow-induced transition in a three-dimensional boundary layer employing unsteady control vortices are investigated by means of direct numerical simulations.
Journal ArticleDOI
Experimental and numerical study of coherent structures in a roughness induced transition boundary layer at Mach 5
Xiaohui Zhao,Qinghu Zhang +1 more
TL;DR: In this article, a wind tunnel experiment and large eddy simulation are carried out for the investigations of a Mach 5 boundary layer transition flow induced by distributed ramp shaped roughness elements.
Journal ArticleDOI
A robust method for reliable transition detection in temperature-sensitive paint data
TL;DR: In this paper, the transition location is determined at the location corresponding to the maximal value of the streamwise gradient of the surface temperature in the transitional region, and the robustness of the transition detection method was proven for a challenging case with low signal-to-noise ratio and moderate streamwise temperature gradients.
References
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Journal ArticleDOI
Stability and transition of three-dimensional boundary layers
TL;DR: The recent progress in three-dimensional boundary-layer stability and transition is reviewed in this paper, focusing on the crossflow instability that leads to transition on swept wings and rotating disks.
Journal ArticleDOI
Basic experiments on transition in three-dimensional boundary layers dominated by crossflow instability
TL;DR: In this article, a review of the results of basic experiments on the transition process in three-dimensional boundary layers governed by crossflow instability is presented, with a detailed description of the essential physical features rather than a complete survey on all the experiments known so far.
Journal ArticleDOI
Disturbance growth in an unstable three-dimensional boundary layer and its dependence on environmental conditions
H. Deyhle,H. Bippes +1 more
TL;DR: In this article, the three-dimensional boundary layer of a swept flat plate with the pressure gradient induced from outside is investigated to enhance knowledge of the transition process in the presence of pure crossflow instability.
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Secondary instability of crossflow vortices and swept-wing boundary-layer transition
TL;DR: The role of secondary instability in transition prediction is theoretically examined for the recent swept-wing experimental data by Reibert et al. as discussed by the authors, who used non-linear parabolized stability equations to compute a new basic state for the secondary instability analysis based on a two-dimensional eigenvalue approach.
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Crossflow disturbances in three-dimensional boundary layers: nonlinear development, wave interaction and secondary instability
TL;DR: In this paper, the authors investigated the nonlinear stability of a model swept-wing boundary layer subject to crossflow instability by numerically solving the governing partial differential equations and found that the three-dimensional boundary layer is unstable to both stationary and travelling crossflow disturbances.