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free-stream turbulence Effects on the Boundary Layer of a High-lift Low-Pressure-Turbine Blade

Journal of Thermal Science 2016年第3期25卷 195-206页

作者： Simoni D. Ubaldi M. Zunino p. Ampellio E. DIME-Universita di Genova Via MontaUegro 11-16145 GenovaItaly GE AvioAero S.p.A. V.I Maggio99 1-10040 Rivalta(TO)-Italy

The suction side boundary layer evolution of a high-lift low-pressure turbine cascade has been experimentally in- vestigated at low and high free-stream turbulence intensity conditions. Measurements have been carded out in order to analyze the boundary layer transition and separation processes at a low Reynolds nttmber, under both steady and unsteady inflows. Static pressure distributions along the blade surfaces as well as total pressure distri- butions in a downstream tangential plane have been measured to evaluate the overall aerodynamic efficiency of the blade for the different conditions. Particle. Image Velocimetry has been adopted to analyze the time-mean and time-varying velocity fields. The flow field has been surveyed in two orthogonal planes （a blade-to-blade plane and a wall-parallel one）. These measurements allow the identification of the Kelvin-Helmholtz large scale cohe- rent structures shed as a consequence of the boundary layer laminar separation under steady inflow, as well as the investigation of the three-dimensional effects induced by the intermittent passage of low and high speed streaks. A close inspection of the time-mean velocity profiles as well as of the boundary layer integral parameters helps to characterize the suction side boundary layer state, thus justifying the influence of free-stream turbulence intensity on the blade aerodynamic losses measured under steady and unsteady inflows.

关键词： profile losses high-lift profiles free-stream turbulence streaks unsteady flows.

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Mechanism of three-dimensional boundary-layer receptivity

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Applied Mathematics and Mechanics(English Edition) 2017年第9期38卷 1213-1224页

作者： Luyu SHEN Changgen LU School of Marine Sciences Nanjing University of Information Science&TechnologyNanjing 210044China

Boundary-layer receptivity is always a hot issue in laminar-turbulent tran- sition. Most actual laminar-turbulent transitions belong to three-dimensional flows. An infinite back-swept fiat-plate boundary layer is a typical three-dimensionalflow. Study of its receptivity is important both in theory and applications. In this paper, a free- stream turbulence model is established. A modified fourth-order Runge-Kutta scheme is used for time marching, and compact finite difference schemes are used for space dis- cretization/ On these bases, whether unsteady cross-flow vortices can be excited in the three-dimensional boundary layer （the infinite back-swept flat-plate boundary layer） by free-stream turbulence is studied numerically. If so, effects of the level and the direc- tion of free-stream turbulence on the three^dimensional boundary-layer receptivity are further studied. Differences of the three-dimensional boundary-layer receptivity are then discussed by considering the non-parallel effect, influence of the leading-edge stagnation point of the flat plate, and variation of the back-swept angle separately. Intensive studies on the ＇three-dimensional boundary-layer receptivity will benefit the development of the hydrodynamic stability theory, and provide a theoretical basis for prediction and control of laminar-turbulent transition.

关键词： receptivity three-dimensional boundary layer free-stream turbulence

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On bypass transition in separation bubbles:a review

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Propulsion and Power Research 2019年第1期8卷 23-34页

作者： Zhiyin Yang Department of Mechanical Engineering and the Built Environment College of Engineering and Technology.University of DerbyDerbyUK

Transition from laminar flow to turbulent flow is of great practical interest as it occurs in many engineering flows and often plays a critical role in aerodynamics and heat transfer performance of those flow *** could be many routes through transition,depending on flow configuration,geometry and the way in which transition is initiated by a wide range of possible background disturbances such as free-stream turbulence,pressure gradient,acoustic noise,wall roughness and obstructions,periodic unsteady disturbance and so *** paper presents a brief overview of wall bounded flow transition in general and focuses more on the transition process in the free shear layer of separation bubbles,demonstrating that at elevated free-stream turbulent intensity the so called bypass transition could occur in geometrically induced separation bubbles where the separation point is fixed.

关键词： Transition Bypass transition Separated free shear layer Separation bubbles free-stream turbulence

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