Flow separation

About: Flow separation is a research topic. Over the lifetime, 16708 publications have been published within this topic receiving 386926 citations.

Approach to an asymptotic state for zero pressure gradient turbulent boundary layers

Abstract: Flat plate turbulent boundary layers under zero pressure gradient at high Reynolds numbers are studied to reveal appropriate scale relations and asymptotic behaviour. Careful examination of the skin-friction coefficient results confirms the necessity for direct and independent measurement of wall shear stress. We find that many of the previously proposed empirical relations accurately describe the local Cf behaviour when modified and underpinned by the same experimental data. The variation of the integral parameter, H, shows consistent agreement between the experimental data and the relation from classical theory. In accordance with the classical theory, the ratio of D and d asymptotes to a constant. Then, the usefulness of the ratio of appropriately defined mean and turbulent time-scales to define and diagnose equilibrium flow is established. Next, the description of mean velocity profiles is revisited, and the validity of the logarithmic law is re-established using both the mean velocity profile and its diagnostic function. The wake parameter, P, is shown to reach an asymptotic value at the highest available experimental Reynolds numbers if correct values of logarithmic-law constants and an appropriate skin-friction estimate are used. The paper closes with a discussion of the Reynolds number trends of the outer velocity defect which are important to establish a consistent similarity theory and appropriate scaling.

Foundations of aerodynamics: bases of aerodynamic design

Abstract: The Fluid Medium. Kinematics of a Flow Field. Dynamics of Flow Fields. Irrotational Incompressible Flow About Two-Dimensional Bodies. Aerodynamic Characteristics of Airfoils. The Finite Wing. Introduction to Compressible Fluids. Energy Relations. Some Applications of One-Dimensional Compressible Flow. Waves. Linearized Compressible Flow. Airfoils in Compressible Flows. Wings and Wing-Body Combinations in Compressible Flow. The Dynamics of Viscous Fluids. Incompressible Laminar Flow in Tubes and Boundary Layers. Laminar Boundary Layers in Compressible Flow. Flow Instabilities and Transition from Laminar to Turbulent Flow. Turbulent Flows. Airfoil Design, Multiple Surfaces, Vortex Lift, Secondary Flows, Viscous Effects. Appendices. Tables. Oblique Shock Chart. References. Index.

Flying-Hot-wire Study of Flow Past an NACA 4412 Airfoil at Maximum Lift

Abstract: Hot-wire measurements have been made in the boundary layer, the separated region, and the near wake for flow past an NACA 4412 airfoil at mad mum lift. The Reynolds number based on chord was about 1,500,000. Special care was taken to achieve a two-dimensional mean flow. The main instrumentation was a flying hot wire; that is, a hot-wire probe mounted on the end of a rotating arm. The probe velocity was sufficiently high to avoid the usual rectification problem by keeping the relative flow direction always within a range of ± 30 deg from the probe ads. A digital computer was used to control synchronized sampling of hot-wire data at closely spaced points along the probe arc. Ensembles of data were obtained at several thousand locations in the flowfield. The data include Intermittency, two components of mean velocity, and twelve mean values for double, triple, and quadruple products of two velocity fluctuations. No Information was obtained about the third (spanwise) velocity component. An unexpected effect of rotor interference was identified and brought under reasonable control. The data are available on punched cards in raw form and also after use of smoothing and interpolation routines to obtain values on a fine rectangular grid aligned with the airfoil chord. The data are displayed In the paper as contour plots.