High resolution LDA measurements in transitional oblique shock wave boundary layer interaction

Abstract

Spatial development of a transitional Oblique Shock Wave Interaction at Mach 1.68 is presented. This type of flow is characterised by very small length scales (boundary layer thickness is smaller than 1mm), high velocities, reverse flows and a wide range of velocity fluctuations along the transition process. Unsteady velocity fields have been obtained using a high spatial resolution Laser Doppler Anemometry system, allowing quantitative measurements of the velocity fluctuations down to y/δ = 0.1. A model to take into account the finite size of the probe volume on the mean and RMS velocity measurements is used and applied to the present measurements. Finally, the amplification of the velocity fluctuations along the transitional separated shear layer is described.

The effect of flow confinement on laminar shock-wave/boundary-layer interactions

“…While many real-world applications will be fully turbulent, laminar solutions provide useful comparisons to wind tunnel experiments where smallscale models are investigated at lower Reynolds numbers. Examples of laminar and tripped-transitional experiments in supersonic SBLI include Hakkinen et al (1959), Degrez et al (1987), Giepman et al (2015Giepman et al ( , 2016Giepman et al ( , 2018, and Diop et al (2019), in which the interactions are not fully turbulent. Furthermore, shock and expansion wave patterns are easier to distinguish in the absence of turbulence and the mechanism of transition can be investigated in laminar SBLI.…”

Experimental and Numerical Investigation of the Diffusion of a Confined Wall Jet through a Perforated Plate

“…To cite a few we can distinguish the error relative to the velocity gradient inside the measurement volume and the intrinsic error related to the BSA post-processing. A detailed analysis of the bias error related to the LDA measurements is given in Diop et al [28]. On the one hand, it is shown that the mean velocity is not biased.…”

A novel laser Doppler anemometer (LDA) for high-accuracy turbulence measurements

“…The LDA is operated in the burst-mode [24] consists of a continuous wave laser beam with wavelength, λ = 532 nm split into two coherent beams. The two beams are directed through a dual Bragg cell (BC in the following) in order to distinguish the moving direction of the particles along the measured component axis [25,26]. This issue was remarked to be critical, in particular within the flow region where fluctuations and turbulence intensities are high [27], since the velocity variations are more likely to exist in both directions.…”