Experimental Studies of Transitional Boundary Layer Shock Wave Interactions

Abstract

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources. gathenng and maintaining the data needed, and completing and reviewing this collection of information. AFRL-SR-AR-TR08-O109 SUPPLEMENTARY NOTES ABSTRACTTransitional shock wave / boundary layer interactions are studied with planar imaging techniques. The interaction is generated by a cylinder mounted on a flat plate in a Mach 5 flow. Planar laser scattering (PLS) and particle image velocimetry (PIV) are used to visualize the flow structure. Images are obtained in streamwise-spanwise planes (plan view). Earlier work focused on investigating similar interactions with tripped boundary layers, whereas the current work focuses on the case where transition occurs naturally.. One goal of this preliminary study was to see if repeatable interactions could be generated.. Imaging was conducted for three downstream locations of the cylinder. The PLS imaging revealed that the transitional interactions resulting from an untripped boundary layer are similar to those generated by tripping. In general it is observed that the separated flow region of transitional interactions exhibits larger variations in their scale and shape than fully turbulent interactions. When the cylinder is farthest upstream (5.3 diameters from leading edge) two types of separation shock are seen: an apparently laminar shock along the plate centerline and a turbulent one in the outboard region. As the cylinder is moved downstream (10.7 diameters), this dual structure is not as apparent, which is consistent with the upstream boundary layer becoming more turbulent. Finally, at 16 diameters downstream the interaction exhibits extreme variations in its shape, which we believe to be caused by sidewall interference. The PIV measurements largely confirm these qualitative observations. SUBJECT TERMS

Progress in shock wave/boundary layer interactions

“…Many are taken from the work of the author and his collaborators mainly because of their ready availability -their selection is not meant to construe that they are necessarily first or most illustrative in their class. Transitional interactions are not discussed although such SBLI interactions have been examined experimentally (for example near a blunt fin in a supersonic stream by Murphree et al [26]) and computationally (for example an impinging shock case by Teramoto [27]). Finally, in the interest of brevity, many insightful efforts could not be included and some conclusions are stated without elaboration of some of the qualifications noted in the cited work: there is thus a necessary if undesirable degree of generalization.…”

Simulation and stability analysis of oblique shock-wave/boundary-layer interactions at Mach 5.92

“…Interactions with hypersonic boundary layers at transitional Reynolds numbers can produce complex and unexpected behavior. For example, recent experiments of hypersonic boundary layer flow past cylindrical posts remain well-behaved if the incoming boundary layer is either laminar or fully turbulent, but show complex behavior if the boundary layer is in a transitional state [20,21]. In the experiment, the cylindrical posts create complicated interactions between bow shocks and recirculation bubbles.…”

Numerical Modelling of Shock Wave Boundary Layer Interactions in Aero-Engine Intakes at Incidence

“…Most of the work on SWBLIs done over the past 50 years has been in fully developed turbulent flows, since most practical applications are at transonic and low supersonic speeds with large Re, where turbulent flow is the norm [60]. In fact, for most cases, transitions trips are used in experimental works to ensure transition location is fixed, and downstream interactions are fully turbulent [11].…”

“…In fact, for most cases, transitions trips are used in experimental works to ensure transition location is fixed, and downstream interactions are fully turbulent [11]. As a result, transitional SWBLIs have received little attention and Murphree et al [60] state that our current understanding of transitional SWBLIs is extremely poor, and that at this stage, simulations cannot be used with any measure of confidence to predict such flows. The boundary layers on intake lips at incidence are believed to be in a transitional state at the point of SWBLI, furthered by the effects of laminarisation, and so increased understanding of transitional SWBLIs is essential for future intake designs.…”

“…In addition to a lack of applications, shortage of research on transitional SWBLIs can also be attributed to the formidable challenge they pose to both experiment and computations [60]. Predictive tools must be able to provide for accurate laminar turbulent boundary behaviour (i.e.…”