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K. P. J. Reddy

Bio: K. P. J. Reddy is an academic researcher from Indian Institute of Science. The author has contributed to research in topics: Hypersonic speed & Expansion tunnel. The author has an hindex of 20, co-authored 54 publications receiving 914 citations.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the effect of aerospikes/aerodisk assemblies as retractable drag-reduction devices for large-angle blunt cones flying at hypersonic Mach numbers is investigated experimentally in a hypersenic shock tunnel HST2.
Abstract: Effectiveness of aerospikes/aerodisk assemblies as retractable drag-reduction devices for large-angle blunt cones flying at hypersonic Mach numbers is investigated experimentally in hypersonic shock tunnel HST2 using a 120-deg apex-angle blunt cone. An internally mounted accelerometer balance system has been used for measuring the aerodynamic drag on the blunt cone with and without forward-facing aerospikes at various angles of attack. The measurements indicate around 55% reduction in drag for the blunt cone with flat-disk spike at zero degree angle of attack for a freestream Mach number of 5.75. Surface convective heat-transfer rate measurements have been carried out on the blunt cone with a flat-disk tipped spike of varying length in order to locate the shock reattachment point on the blunt-cone surface. The measured heat-transfer rates fluctuate by about ±20% in the separated flow region as well as near the reattachment point indicating the unsteady flowfleld around the spiked blunt cone. The shock structure around the 120-deg apex-angle blunt cone with a 12-mm-long flat-tipped aerospike has also been visualized using the electric discharge technique. The visualized shock structure and the measured drag on the blunt cone with aerospikes agree well with the axisymmetric numerical simulations

114 citations

Journal ArticleDOI
TL;DR: In this article, the aerodynamic drag force is measured using the accelerometer based force balance system and the experimental measurements show about 30% −45% reduction in drag coefficient for different jet pressures.
Abstract: Counterflow drag reduction by supersonic jet for a large angle blunt cone at hypersonic Mach number is investigated in a shock tunnel. The flowfields around the test model in the hypersonic flow with an opposing supersonic jet emanating from the stagnation point of the model are visualized by high speed schlieren technique. The aerodynamic drag force is measured using the accelerometer based force balance system. The experimental measurements show about 30%–45% reduction in drag coefficient for different jet pressures.

91 citations

Journal ArticleDOI
TL;DR: A miniature three-component accelerometer balance system for measuring the fundamental aerodynamic force coefficients over blunt bodies has been designed, fabricated and tested in the Indian Institute of Science hypersonic shock tunnel HST2 at a nominal Mach number of 5.75 as mentioned in this paper.
Abstract: A miniature three-component accelerometer balance system for measuring the fundamental aerodynamic force coefficients over blunt bodies has been designed, fabricated and tested in the Indian Institute of Science hypersonic shock tunnel HST2 at a nominal Mach number of 5.75. The model and the balance system are supported by rubber bushes, thereby ensuring unrestrained free-floating conditions of the model in the test section during the flow duration. Exhaustive axisymmetric finite-element simulations are carried out to select appropriate rubber bushes and materials for the model and the balance system. The internally mountable accelerometer balance is used to measure the drag, lift and pitching moment coefficients for a $60^o$ apex angle blunt cone within the effective tunnel test time of $800\hspace{2mm}{\mu}s$. The measured aerodynamic force coefficients match very well with the theoretical values predicted using modified Newtonian theory at moderate specific enthalpy levels of the test gas.

67 citations

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TL;DR: In this article, the effects of a forward-racing cavity on heat transfer and aerodynamic coefficients are addressed in a blunt-nosed hypersonic missile mounted with a forwardfacing cavity.
Abstract: A blunt-nosed hypersonic missile mounted with a forward-facing cavity is a good alternative to reduce the stagnation heating rates. The effects of a forward-racing cavity on heat transfer and aerodynamic coefficients are addressed in this paper. Tests were carried out in hypersonic shock tunnel HST2, at a hypersonic Mach number of 8 using a 41 deg apex-angle blunt cone. The aerodynamic forces on the test model with and without a forward-facing cavity at various angles of attack are measured by using an internally mountable accelerometer force balance system. Heat flux measurements have been carried out on the test model with and without a forward-facing cavity of the entire surface at zero degree angle of attack with platinum sensors. A numerical simulation was also carried out using the computational fluid dynamics code (CFX-Ansys 5.7). An important result of this study is that the smaller cavity diameter has the highest lift-to-drag ratio, whereas the medium cavity has the highest heat flux reduction. Theshock structure around the test model has also been visualized using the Schlieren flow visualization technique. The visualized shock structure and the measured aerodynamic forces on the missile-shaped body with cavity configurations agree well with the axisymmetric numerical simulations.

59 citations

Journal ArticleDOI
TL;DR: In this article, a three-component accelerometer balance system is used to study the drag reduction effect of an aerodisc on large angle blunt cones flying at hypersonic Mach numbers.
Abstract: A three-component accelerometer balance system is used to study the drag reduction effect of an aerodisc on large angle blunt cones flying at hypersonic Mach numbers. Measurements in a hypersonic shock tunnel at a freestream Mach number of 5.75 indicate more than 50% reduction in the drag coefficient for a 120degrees apex angle blunt cone with a forward facing aerospike having a flat faced aerodisc at moderate angles of attack. Enhancement of drag has been observed for higher angles of attack due to the impingement of the flow separation shock on the windward side of the cone. The flowfields around the large angle blunt cone with aerospike assembly flying at hypersonic Mach numbers are also simulated numerically using a commercial CFD code. The pressure and density levels on the model surface, which is under the aerodynamic shadow of the flat disc tipped spike, are found very low and a drag reduction of 64.34% has been deduced numerically.

55 citations


Cited by
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Journal ArticleDOI
TL;DR: An up-to-date review of the literature available on the subject of ethanol to ethylene can be found in this paper, where the authors present an overview of the current state-of-the-art in this area.
Abstract: This article is an up-to-date review of the literature available on the subject of ethanol to ethylene. The process of ethanol to ethylene has broad development prospects. Compared with the process of petroleum to ethylene, ethanol dehydration to ethylene is economically feasible. Researchers have been redirecting their interest to the ethylene production process, catalysts, and reaction mechanisms. A fluidized bed reactor, together with a wear-resistant, efficient, and stable catalyst will be the focus of future research that includes a deep understanding of the large-scale activated alumina catalyst and the molecular sieve catalyst used, and will promote the development of the ethanol dehydration to ethylene process and provide strong support for the market competiveness of the process.

337 citations

Journal ArticleDOI
TL;DR: In this paper, a general trajectory surface hopping methodology, termed SHARC, which is able to include nonadiabatic and spin-orbit couplings in excited state dynamics simulations, is explained in detail.
Abstract: Intersystem crossing is a radiationless process that can take place in a molecule irradiated by UV-Vis light, thereby playing an important role in many environmental, biological and technological processes. This paper reviews different methods to describe intersystem crossing dynamics, paying attention to semiclassical trajectory theories, which are especially interesting because they can be applied to large systems with many degrees of freedom. In particular, a general trajectory surface hopping methodology recently developed by the authors, which is able to include nonadiabatic and spin-orbit couplings in excited-state dynamics simulations, is explained in detail. This method, termed SHARC, can in principle include any arbitrary coupling, what makes it generally applicable to photophysical and photochemical problems, also those including explicit laser fields. A step-by-step derivation of the main equations of motion employed in surface hopping based on the fewest-switches method of Tully, adapted for the inclusion of spin-orbit interactions, is provided. Special emphasis is put on describing the different possible choices of the electronic bases in which spin-orbit can be included in surface hopping, highlighting the advantages and inconsistencies of the different approaches. © 2015 Wiley Periodicals, Inc.

212 citations

Journal ArticleDOI
TL;DR: The objective of this work is to provide a literature survey on the research attempts made in the field of ejector refrigeration systems and the studies made on the ejector as a component.

202 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a survey of the use of spikes for reducing both the drag and the aeroheating by modifying the flowfield ahead of the vehicle's nose.

150 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present a comprehensive literature review on three active cooling methods, i.e., regenerative cooling, film cooling, and transpiration cooling, including the fluids flow, heat transfer, and thermal cracking characteristics of different hydrocarbon fuels.

148 citations