High-Reynolds-number flat-plate turbulent boundary layer measurements (original) (raw)
Turbulence profiles from a smooth flat-plate turbulent boundary layer at high Reynolds number
Experimental Thermal and Fluid Science, 2012
Much is known about smooth-flat-plate turbulent boundary layers (TBLs) at laboratory-scale Reynolds numbers because of a wealth of experimental data. However, smooth-flat-plate TBL data are much less common at the high Reynolds numbers typical of aerodynamic and hydrodynamic applications (Re x $ 10 8-10 10), and at the even higher Reynolds numbers of many geophysical flows. This paper presents new LDV-measured profiles of the stream-wise velocity variance, the wall-normal velocity variance, and the Reynolds shear stress from the TBL that formed on a smooth flat plate at Karman numbers from 15,000 to 60,000 (Re x from 75 million to 220 million). The experiments were conducted in the William B. Morgan Large Cavitation Channel on a polished (k + < 0.2) flat-plate test model 12.9 m long and 3.05 m wide at water flow speeds up to 20 m s À1. The TBL on the model developed in a mild favorable pressure gradient having an acceleration parameter K $ 10 À10. When plotted with the usual inner and outer scalings, the stream-wise velocity variance profiles display a Reynolds number dependence that is consistent with prior lower Reynolds-number zero-pressure-gradient TBL measurements. However, using the same normalizations, the profiles of wall-normal velocity variance and Reynolds shear stress are found to be Reynolds number independent, or nearly so, when experimental uncertainties are considered.
On the turbulent boundary layer over a flat plate at moderate Reynolds numbers
Physics of Fluids
Two separate experimental campaigns of a spatially developing turbulent boundary layer under approximately zero-pressure-gradient at moderate Reynolds numbers ([Formula: see text]) are conducted with stereoscopic Particle Image Velocimetry (PIV) and one component Hot Wire Anemometry. This range of Reynolds numbers is found to be of particular interest for turbulent boundary layer control investigations. The motivations behind this work rely on the lack of recent studies that provide a rigorous experimental database on a flat plate turbulent boundary layer, openly available online. This is critical as, in most of the cases, the modification of the statistics resulting from turbulent boundary layer control strategies are compared with a smooth baseline reference. The statistics of the velocity fields, obtained with the two techniques, show a good match with the direct numerical simulation in literature results. We focused on the skin friction evaluation by means of Clauser's chart...
Reynolds shear stress measurements in a separated boundary layer flow
22nd Fluid Dynamics, Plasma Dynamics and Lasers Conference, 1991
Turbulence measurements were obtained for two caSes of boundary layer flow with adverse pressure graclient, one attached and the other separated. A threecomponent laser Doppler velocimeter system was used to measure three mean velocity components, all six Reynolds stress components, and all ten velocity triple product correlations. Independent measurements of skin-friction obtained with a laser oil-flow interferometer were used to examine the law of the wall in adverse pressure gradient flows where p+ < 0.05. Strong similarities were seen between the two adverse pressure gradient flows and frce shcar layer type flows. Eddy viscosities, dissipation rates, and pressure-strain rates were deduced from the data and compared to various turbulence modeling assumptions.
Structure of Rough Wall Turbulent Boundary Layers at Relatively High Reynolds Number
The effect of two different types of surface roughness on a turbulent boundary layer was studied using 2-component LDV measurements in a relatively high speed water tunnel. One roughness consists of square bars at a streamwise spacing p equal to 2k (k is the roughness height). The other consists of cylindrical rods with p/k equal to 4. Both roughnesses are aligned in a direction transverse to the flow. Measurements of the turbulent field were carried out over a wide range of Reynolds numbers, (1 500 < R θ < 23 000) based on the momentum thickness. Comparison of the turbulent field between different surfaces is made at R θ ∼ 9 000. This study supports previous attempts to classify rough surfaces according to their turbulence characteristics, and extends them by providing measurements at high Reynolds numbers for three distinct surface conditions.
Journal of Fluid Mechanics, 2019
Streamwise velocity and wall-shear stress are acquired simultaneously with a hot-wire and an array of azimuthal/spanwise-spaced skin friction sensors in large-scale pipe and boundary layer flow facilities at high Reynolds numbers. These allow for a correlation analysis on a per-scale basis between the velocity and reference skin friction signals to reveal which velocity-based turbulent motions are stochastically coherent with turbulent skin friction. In the logarithmic region, the wall-attached structures in both the pipe and boundary layers show evidence of self-similarity, and the range of scales over which the self-similarity is observed decreases with an increasing azimuthal/spanwise offset between the velocity and the reference skin friction signals. The present empirical observations support the existence of a self-similar range of wall-attached turbulence, which in turn are used to extend the model of Baarset al.(J. Fluid Mech., vol. 823, p. R2) to include the azimuthal/spanw...
PIV experiments in rough-wall, laminar-to-turbulent, oscillatory boundary-layer flows
Experiments in Fluids, 2013
Exploratory measurements of oscillatory boundary layers were conducted over a smooth and two different rough beds spanning the laminar, transitional and turbulent flow regimes using a multi-camera 2D-PIV system in a small oscillatory-flow tunnel (Admiraal et al. in J Hydraul Res 44(4):437-450, 2006). Results show how the phase lag between bed shear stress and free-stream velocity is better defined when the integral of the momentum equation is used to estimate the bed shear stress. Observed differences in bed shear stress and phase lag between bed shear stress and free-stream velocity are highly sensitive to the definition of the bed position (y = b). The underestimation of turbulent stresses close to the wall is found to explain such differences when using the addition of Reynolds and viscous stresses to define both the bed shear stress and the phase lag. Regardless of the flow regime, in all experiments, boundary-layer thickness reached its maximum value at a phase near the flow reversal at the wall. Friction factors in smooth walls are better estimated using a theoretical equation first proposed by Batchelor (An introduction to fluid dynamics. Cambridge University Press, Cambridge, 1967) while the more recent empirical predictor of Pedocchi and Garcia (J Hydraul Res 47(4):438-444, 2009a) was found to be appropriate for estimating friction coefficients in the laminar-to-turbulent transition regime. This article is part of the Topical Collection on Application of Laser Techniques to Fluid Mechanics 2012.
Some Reynolds number effects on two- and three-dimensional turbulent boundary layers
Experiments in Fluids, 2001
Experimental data for a two-dimensional (2-D) turbulent boundary layer (TBL)¯ow and a three-dimensional (3-D) pressure-driven TBL¯ow outside of a wing/ body junction were obtained for an approach Reynolds number based on momentum thickness of Re h 23,200. The wing shape had a 3:2 elliptical nose, NACA 0020 pro®led tail, and was mounted on a¯at wall. Some Reynolds number effects are examined using ®ne spatial resolution (Dy + 1.8) three-velocity-component laser-Doppler velocimeter measurements of mean velocities and Reynolds stresses at nine stations for Re h 23,200 and previously reported data for a much thinner boundary layer at Re h 5,940 for the same wing shape. In the 3-D boundary layers, while the stress pro®les vary considerably along the¯ow due to deceleration, acceleration, and skewing, pro®les of the parameter 1=S s=m 2 um 2 mw 2 q =m 2 correlate well and over available Reynolds numbers. The measured static pressure variations on the¯at wall are similar for the two Reynolds numbers, so the vorticity¯ux and the measured mean velocities scaled on wall variables agree closely near the wall. The stresses vary similarly for both cases, but with higher values in the outer region of the higher Re h case. The outer layer turbulence in the thicker high Reynolds number case behaves similarly to a rapid distortion of thē ow, since stream-wise vortical effects from the wall have not diffused completely through the boundary layer at all measurement stations. 2 Design modifications for the five-component LDV system The ®ve-component laser-Doppler velocimeter (5CLDV) that was used for the near-wall measurements