Turbulent Boundary Layer Characteristics at High Reynolds Number


Book Description

The pressure gradient effect on the characteristics of a compressible turbulent boundary layer in separation and reattachment regions of laminar and turbulent flows have been investigated. Experiments were conducted at a large variation of Mach numbers and free stream Reynolds numbers. Favorable pressure gradient was found to have significant effect on the correlation of the total temperature and velocity profiles in turbulent boundary layer. Correlations for the separation distance, peak heating values, and peak surface pressure were found. Methods are described to predict the location and peak heating values in a separated flow region.




Experimental Study on High Subsonic Turbulent Flow Incipient Separation


Book Description

For flow over a two-dimensional ramp compression corner case, an experimental investigation to determine the incipient separation was carried out at Mach numbers between 0.55 and 0.9 and Reynolds numbers (based on undisturbed boundary layer thickness) between 350,000 and 690,000. Detailed surface pressure, pitot traversing and oil flow data were obtained for each ramp angle case. Two-dimensionality of the ramp compression corners was verified by the surface oil flow. A major finding of this study is that the incipient separation ramp angle is relatively independent of Mach number and Reynolds number within the range studied. The incipient separation ramp angle was found to be about 22.5 degrees.










Experimental Investigation of Turbulent Boundary Layer with Uniform Blowing at Moderate and High Reynolds Numbers


Book Description

Experimental investigation in turbulent boundary layer flows represents one of the canonical geometries of wall bounded shear flows. Utmost relevance of such experiments, however, is applied in the engineering applications in aerospace and marine industries. In particular, continuous effort is being imparted to explore the underlying physics of the flow in order to develop models for numerical tools and to achieve flow control. Flow control experiments have been widely investigated since 1930's. Several flow control technique has been explored and have shown potential benefit. But the choice of control technique depends largely on the boundary condition and the type of application. Hence, friction drag of subsonic transport aircraft is intended to be reduced within the scope of this Ph. D. topic. Therefore, application of active control method such as microblowing effect in the incompressible, zero pressure gradient turbulent boundary layer was investigated. A series of experiments have been performed in two different wind tunnel facilities. Wind tunnel from Department of Aerodynamics and Fluid Mechanics (LAS) was used for the measurements for moderate Reynolds number range in co-operation with the wind tunnel from Laboratoire de M ́ecanique de Feiret Lille for large Reynolds number range. Measurements are conducted with the help of state-of-the-art techniques such as Laser Doppler Anemometry, Particle Image Velocimetry and electronic pressure sensors.







Viscous Flow Interaction Studies


Book Description

The research was designed to gain understanding of the flow of air at high speeds over the components of lifting supersonic and hypersonic vehicles--wings, flaps, fins, inlets--and their interactions with respect to heating, surface friction, pressure, and aerodynamic forces. The objective was to help predict (a) flows on complex aerospace vehicle configurations in high-speed flight and (b) the location of areas of high heating. The research covers the areas of laminar and turbulent boundary layers, boundary layer transition, boundary layer separation, base flows and wakes, low density flows, three-dimensional interactions, viscous flow problems, and some flow measurement techniques.




Boundary-Layer Separation


Book Description

The IUTAM Symposium on Boundary-Layer Separation, suggested by the UK National Committee of Theoretical and Applied Mechanics and supported by the International Union of Theoretical and Applied Mechanics, was held at University College London on August 26-28, 1986. The proposed theme and scope of the Symposium were designed to help to bring about the necessary interaction between experimentalists, computationalists and theoreticians for the furthering of understanding in this challenging subject. The talks and discussions were aimed at representing the very wide range and application of separating-flow phenomena, which often substantially affect the whole of fluid dynamics at medium to large Reynolds numbers, covering in particular both laminar and turbulent flow, steady or unsteady, two- or three-dimensional, small or large-scale, incompressible or compressible, external or internal, from the experimental, computational and theoretical standpoints. It was intended that about 80 scientists would participate in the Symposium, with about 25 talks being delivered, to which poster sessions with 8 contributions were added subsequently. All the speakers and poster presenters were selected by the scientific committee, although two late replacements of speakers were required. Fruitful discussions, well led by the session chairmen, took place formally after each talk and after the poster sessions and informally on other occasions including the social events. The present proceedings of the Symposium appear to reflect much of the current state of experimental, computational and theoretical work and progress in boundary-layer separation. We hope that they provide also ideas, questions and stimulation, in addition to major recent developments.