The Experts below are selected from a list of 111 Experts worldwide ranked by ideXlab platform
Ch J Robinet - One of the best experts on this subject based on the ideXlab platform.
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bifurcations in shock wave Laminar Boundary Layer interaction global instability approach
Journal of Fluid Mechanics, 2007Co-Authors: Ch J RobinetAbstract:The principal objective of this paper is to study some unsteady characteristics of an interaction between an incident oblique shock wave impinging on a Laminar Boundary Layer developing on a flat plate. More precisely, this paper shows that some unsteadiness, in particular the low-frequency unsteadiness, originates in a supercritical Hopf bifurcation related to the dynamics of the separated Boundary Layer. Various direct numerical simulations were carried out of a shock-wave/Laminar-Boundary-Layer interaction (SWBLI). Three-dimensional unsteady Navier-Stokes equations are numerically solved with an implicit dual time stepping for the temporal algorithm and high-order AUSMPW+ scheme for the spatial discretization. A parametric study on the oblique shock-wave angle has been performed to characterize the unsteady behaviour onset. These numerical simulations have shown that starting from the incident shock angle and the spanwise extension, the flow becomes three-dimensional and unsteady. A linearized global stability analysis is carried out in order to specify and to find some characteristics observed in the direct numerical simulation. This stability analysis permits us to show that the physical origin generating the three-dimensional characters of the flow results from the existence of a three-dimensional stationary global instability.
Gareth H Mckinley - One of the best experts on this subject based on the ideXlab platform.
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drag reduction using wrinkled surfaces in high reynolds number Laminar Boundary Layer flows
Physics of Fluids, 2017Co-Authors: Shabnam Raayaiardakani, Gareth H MckinleyAbstract:Inspired by the design of the ribbed structure of shark skin, passive drag reduction methods using stream-wise riblet surfaces have previously been developed and tested over a wide range of flow conditions. Such textures aligned in the flow direction have been shown to be able to reduce skin friction drag by 4%–8%. Here, we explore the effects of periodic sinusoidal riblet surfaces aligned in the flow direction (also known as a “wrinkled” texture) on the evolution of a Laminar Boundary Layer flow. Using numerical analysis with the open source Computational Fluid Dynamics solver OpenFOAM, Boundary Layer flow over sinusoidal wrinkled plates with a range of wavelength to plate length ratios ( λ / L ), aspect ratios ( 2 A / λ ), and inlet velocities are examined. It is shown that in the Laminar Boundary Layer regime, the riblets are able to retard the viscous flow inside the grooves creating a cushion of stagnant fluid that the high-speed fluid above can partially slide over, thus reducing the shear stress in...
Robert W. Maccormack - One of the best experts on this subject based on the ideXlab platform.
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Numerical solution of the interaction of a shock wave with a Laminar Boundary Layer
Proceedings of the Second International Conference on Numerical Methods in Fluid Dynamics, 1Co-Authors: Robert W. MaccormackAbstract:Shock wave interaction with Laminar Boundary Layer on flat plate using modified Lax-Wendroff difference technique
Chiang C Mei - One of the best experts on this subject based on the ideXlab platform.
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numerical study of Laminar Boundary Layer flows over a superhydrophobic plate
Physics of Fluids, 2018Co-Authors: Chiang C Mei, Xiaoxian GuoAbstract:Liquid flow in the Laminar Boundary Layer over a flat plate with a superhydrophobic surface formed by a square array of pillars is studied theoretically. Assuming the water surface on top of the pillars to be in the Cassie-Baxter state, asymptotic analysis is first carried out to separate the micro-scale flow in a typical cell surrounding a pillar and the macro-scale development of the Laminar Boundary Layer of Blasius type. The 3-D cell problem and the 2-D Boundary Layer problem are solved together iteratively, yielding the slip length and the entire flow field. Numerical results are presented to examine the effect of solid fraction, pillar-to-pillar spacing, and the speed of the ambient flow on drag reduction. It is shown that the slip length is practically constant, while the Boundary Layer thickness grows monotonically downstream so that hydrophobicity affects drag reduction primarily over the leading portion of a long surface.
Doyle Knight - One of the best experts on this subject based on the ideXlab platform.
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shock wave Laminar Boundary Layer interaction over a double wedge in a high mach number flow
52nd AIAA Aerospace Sciences Meeting - AIAA Science and Technology Forum and Exposition SciTech 2014, 2014Co-Authors: Mohammad Ali Badr, Doyle KnightAbstract:Shock wave Laminar Boundary Layer interaction (SWBLI) over a double wedge at Mach 7.14 and 7.11 were simulated using the commercial flow solver GASPex. An inviscid simulation was performed at Mach 7.14 for validation. Results for the region downstream of the first shock wave show less than one percent error in comparison with oblique shock wave theory. Laminar perfect gas simulations were performed for stagnation enthalpies of 2 MJ/kg and 8 MJ/kg. The computed heat transfer distribution agrees closely with the experiment upstream of the shock wave Laminar Boundary Layer interaction; however, significant differences are evident in the region of the interaction. In particular, the timeaccurate simulations indicate a significantly longer physical time to achieve steady state than observed in the experiment.
