The relationship between the upstream boundary layer and the low-frequency, large-scale unsteadiness of the separated flow in a Mach 2 compression ramp interaction is investigated by performing wide-field particle image velocimetry (PIV) and planar laser scattering (PLS) measurements in streamwise–spanwise planes. Planar laser scattering measurements in the upstream boundary layer indicate the presence of spanwise strips of elongated regions of uniform momentum with lengths greater than 40?. These long coherent structures have been observed in a Mach 2 supersonic boundary layer (Ganapathisubramani, Clemens & Dolling 2006) and they exhibit strong similarities to those that have been found in incompressible boundary layers (Tomkins & Adrian 2003; Ganapathisubramani, Longmire & Marusic 2003). At a wall-normal location of y/?=0.2, the inferred instantaneous separation line of the separation region is found to oscillate between x/?=?3 and ?1 (where x/?=0 is the ramp corner). The instantaneous spanwise separation line is found to respond to the elongated regions of uniform momentum. It is shown that high- and low-momentum regions are correlated with smaller and larger size of the separation region, respectively. Furthermore, the instantaneous separation line exhibits large-scale undulations that conform to the low- and high-speed regions in the upstream boundary layer. The low-frequency unsteadiness of the separation region/shock foot observed in numerous previous studies can be explained by a turbulent mechanism that includes these elongated regions of uniform momentum

Effects of upstream boundary layer on the unsteadiness of shock induced separation

There is urgency for the development of nanomaterials that can meet emerging biomedical needs. Magnetic nanoparticles (MNPs) offer high magnetic moments and surface-area-to-volume ratios that make them attractive for hyperthermia therapy of cancer and targeted drug delivery. Additionally, they can function as contrast agents for magnetic resonance imaging (MRI) and can improve the sensitivity of biosensors and diagnostic tools. Recent advancements in nanotechnology have resulted in the realization of the next generation of MNPs suitable for these and other biomedical applications. This review discusses methods utilized for the fabrication and engineering of MNPs. Recent progress in the use of MNPs for hyperthermia therapy, controlling drug release, MRI, and biosensing is also critically reviewed. Finally, challenges in the field and potential opportunities for the use of MNPs toward improving their properties are discussed.

Magnetic Nanoparticles in Cancer Therapy and Diagnosis.

Experimental investigation on drag and heat flux reduction in supersonic/hypersonic flows: A survey

Heat reduction using conterflowing jet for a nose cone with aerodisk in hypersonic flow

Drag and heat flux reduction mechanism induced by the spike and its combinations in supersonic flows: A review

A simple hand-operated shock tube capable of producing Mach 2 shock waves is described. Performance of this miniature shock tube using compressed high pressure air created by a manually operated piston in the driver section of the shock tube as driver gas with air at 1 atm pressure as the test gas in the driven tube is presented. The performance of the shock tube is found to match well with the theoretically estimated values using normal shock relations. Applications of this shock tube named Reddy tube, include study of blast-induced traumatic brain injuries and high temperature chemical kinetics.

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Manually operated piston-driven shock tube

Investigations on high enthalpy shock wave exposed graphitic carbon nanoparticles

IMPOSED bluntness at the nose of a hypersonic vehicle is necessary to alleviate the oncoming heat load. However, increased wave drag is the immediate consequence of the forced bluntness. Hence, research in the field of hypersonics is always centered on the reduction of wave drag encountered by the space vehicles during their ascent phase. Most of the drag-reduction techniques are directed towards modifying the flowfield ahead of the stagnation point. Among the drag-reduction techniques, retractable spike is the simplest and is an easy-to-implement technique; hence, the forward-facing aerospike technique has attracted many researchers to consider various issues. Various configurations of aerospikes were assessed by Menezes et al. [1] to arrive at the best configuration for drag reduction on a 120 deg apex angle blunt cone, and a flat-disc-tipped aerospike of unity L=D (spike length-to-cone base-diameter ratio) with a disc diameter of 1 4 D was observed to be the most efficient drag-reducing agent. Therefore, a similar flat-disctipped aerospike configuration is considered in the present study to evaluate its effect on drag of a 120 deg apex-angle blunt cone under various total-enthalpy conditions. An accelerometer-based force balance was used to measure drag on the model in a conventional hypersonic shock tunnel, IITB-ST (Indian Institute of Technology Bombay—Shock Tunnel), at low-enthalpy conditions (1:1 0:02 and 1:5 0:03 MJ=kg), and high-enthalpy tests (5 0:44 MJ=kg) were conducted on the same model in a free-piston-driven hypersonic shock tunnel, HST3. Flowfield modifications brought about by the disc-tipped spike were expected to depend on the total enthalpy of the flow, as such a dependence was observed in the case of drag-reduction studies using a fluidic spike [2]. Details of the experimental methodology and the results are presented in the following sections. II. Test Facilities, Model, and Force Balance

Effectiveness of Aerospike for Drag Reduction on a Blunt Cone in Hypersonic Flow

A new two-step procedure for the synthesis of MoS2 nanotubes using lead as a growth promoter is reported. In the first step, molybdenum suboxide nanowhiskers containing a small amount of lead atoms were created by exposing a pressed MoS2+Pb mixture to highly compressed shock-heated argon gas, with estimated temperatures exceeding 9900 K. In the second step, these molybdenum suboxide nanowhiskers served as templates for the sulfidization of the oxide into MoS2 nanotubes (by using H2S gas in a reducing atmosphere at 820 degrees C). Unlike the case of WS2 nanotubes, the synthesis of a pure phase of MoS2 nanotubes from molybdenum oxide has proven challenging, due mostly to the volatile nature of the latter at the high requisite reaction temperatures (>800 degrees C). In contrast, the nature and apparent reaction mechanism of the method reported herein are amenable to future scale-up. The high-temperature shockwave system should also facilitate the synthesis of new nanostructures from other layered materials.

Two‐step Synthesis of MoS2 Nanotubes using Shock Waves with Lead as Growth Promoter

Heat transfer rate and pressure measurements were made upstream of surface protuberances on a flat plate and a sharp cone subjected to hypersonic flow in a conventional shock tunnel. Heat flux was measured using platinum thin-film sensors deposited on macor substrate and the pressure measurements were made using fast acting piezoelectric sensors. A distinctive hot spot with highest heat flux was obtained near the foot of the protuberance due to heavy vortex activity in the recirculating region. Schlieren flow visualization was used to capture the shock structures and the separation distance ahead of the protrusions was quantitatively measured for varying protuberance heights. A computational analysis was conducted on the flat plate model using commercial computational fluid dynamics software and the obtained trends of heat flux and pressure were compared with the experimental observation. Experiments were also conducted by physically disturbing the laminar boundary layer to check its effect on the magnitude of the hot spot heat flux. In addition to air, argon was also used as test gas so that the Reynolds number can be varied.

K. P. J. Reddy

Papers

Manually operated piston-driven shock tube

Investigations on high enthalpy shock wave exposed graphitic carbon nanoparticles

Effectiveness of Aerospike for Drag Reduction on a Blunt Cone in Hypersonic Flow

Two‐step Synthesis of MoS2 Nanotubes using Shock Waves with Lead as Growth Promoter

Investigation of the separated region ahead of three-dimensional protuberances on plates and cones in hypersonic flows with laminar boundary layers