R. Ramesh Babu

Reddy Tube Driven Table-Top Hypersonic Shock Tunnel

A table-top hypersonic shock tunnel driven by a manually operated shock tube of 29 mm diameter, named Reddy tube, is presented. The shock tunnel is capable of generating hypersonic flow of freestream Mach number 5.5 with a test time of 600 microseconds. Measurement of heat transfer rates for a small model is described. The measured stagnation point heat transfer rates of ~10 W/cm2 match with the theoretically estimated values within the experimental errors. The simple table-top hypersonic shock tunnel presented here is ideally suited for the class room experiments in the hypersonic aerodynamics course.

Experiments Using Reddy Tube-Driven Tabletop Hypersonic Shock Tunnel

Drag measurement and flow visualization studies have been carried out using a tabletop hand-operated hypersonic shock tunnel known as “Reddy tube-driven tabletop hypersonic shock tunnel.” A 31 mm inner diameter shock tube used for the present experiments generates a hypersonic flow of Mach 6.5 with a test time of 200 μs. The test model used for the study is a hemisphere of diameter 32 mm. A drag force of approximately 45 N has been measured in the experiments. The theoretically obtained value of drag force matches that of the experiments for the same condition. The results of the drag measurements carried out in Reddy tube-driven tabletop shock tunnel are compared with the results obtained using a conventional shock tunnel. Qualitative flow visualization studies performed using a Z-type schlieren method have also been presented.

A novel approach for human-machine interaction using hand gesture

Human machine interaction is a rapidly developing field. Hand gestures are used to interact with the machine; this makes the human machine interaction very interesting and intuitive. Several devices have been developed in the past using the camera for recognizing hand gestures and communicating with the machine. In this paper we have proposed a new system called hand gesture recognition (HGR) to overcome the use of camera which has several disadvantages like lighting, making proper hand movements before camera, operating in less range. The universal control unit may be as a form of wearable one. A Kalman filtering approach is proposed for stable displacement estimation and waveband classification of the measured acceleration. With the sensors placed in the form of watch or band on our hand, any motion made by the hand will be detected by these sensors and relayed to a control unit to take the required actions. The estimated results are compared with those of a commercial geometry measurement.

Experimental Investigation of Interaction of Shock Heated Test Gases with 7.25 μm Carbon Fibres in a Shock Tube

Designing thermal protection system (TPS) is a challenging task for the success of re-entry space vehicles. The TPS may be ablative or non-ablative heat shield material which is subjected to very high thermal stress at the time of re-entry. The thermal behavior of thick ablating material is strongly related to the flight environment such as the impact pressure, enthalpy of the gas and heat transfer rate from shock layer. The function of the ablative heat shield is to reduce the temperature in the shock layer. Ablation causes the TPS layer to char and sublimate through the process of pyrolysis [1]. The pyrolysis gas produced in the reaction zone of ablator interior is injected into the shock layer and is expected to reduce the net heat flux near the surface. The composite materials using ceramic matrix with high temperature carbon fibers or carbon/carbon have been used for various applications for over three decades. Carbon composite maintains their strength in inert atmospheres up to about 2500 K [2]. The mechanical properties of the composites are affected by damage induced during the oxidation tests [3]. The modern composite materials are available in carbon/carbon composites, ceramic matrix composites made with silicon carbide, silicon nitride and alumina fibers.