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Experimental and Computational Studies on Blunt Body Aerodynamics
G. Rajesh,H. D. Kim(김희동),G. Ramachandran 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
Aerodynamics on blunt body is of practical importance since it contains extremely complicated flow fields such as, shock-shock interactions, shock-boundary layer interactions and shock-shear layer interactions, which often lead to high localized heat transfer rates in the interaction regions. In the present study, both experimental and computational works have been carried out to investigate the aerodynamic characteristics on a blunt body with typical double cone configuration at supersonic speeds. Several interesting shock interaction phenomena are found on the blunt body. A separation shock formed upstream of the separated region which reattaches downstream of the flare section of the blunt body, strongly interacts with the bow shock. It is also found that the viscous effects play a major role in deciding the type of shock-shock interaction pattern at the vicinity of the triple point. The present computational results are in close agreements with the measured force and moments coefficients.
A Computational study of the Gas Flow in a Coanda Ejector
G. Rajesh,J. H. Lee,Y. K. Lee,H. D. Kim(김희동) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
The Coanda effect has been used extensively in various aerodynamic applications to improve the system performance. The primary flow in Coanda ejectors is attached to the ejector wall and is expanded inducing a secondary flow. This will probably lead to the mixing of both primary and secondary flows at a down stream section. Very few works have been reported based on the optimization on such devices. The main objective of the present study is to numerically investigate the flow field on a typical Coanda ejector and validate the results with the available experimental data. Many configurations of the Coanda ejector have been analyzed. The effect of various geometric parameters of the device on the expanding mixing layer has also been obtained. The computed data agree fairly well with the experimental data available.
Computational Study of the Unsteady Projectile Aerodynamics
G. Rajesh,H. G. Kang(강형구),J. M. Lee(이정민),H. D. Kim(김희동) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
A computational fluid dynamics method has been used to simulate the unsteady flow field on a projectile launched from a ballistic range. A moving coordinate scheme for a multi-domain technique was used to study the unsteady flow with moving boundary. The unsteady, axisymmetric Euler equation systems were numerically solved using the third order Chakravarthy-Osher total variation diminishing scheme, with MUSCL approach. Effects of initial pressure and temperature behind the projectile on the flow field were studied. The present results were validated with the available experimental data. The computed results predict the dramatic changes in the flow field when the initial pressure and temperature behind the projectile are varied. For higher pressures and temperatures, the projectile and the blast wave propagation is faster and the supersonic jet in front of the projectile is more under expanded compared to the other cases.
A Theoretical Study for the Design of a New Ballistic Range
G. Rajesh,Y. K. Lee(이영기),S. C. Back(백승철),H. D Kim(김희동) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
The Ballistic Range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile Aerodynamics, creation of new materials, etc, since it can create an extremely high-pressure state in very short time. Of many different types of Ballistic Ranges developed to date, two-stage light gas gun is being employed most extensively. In the current study, a theoretical work has been made to develop a new type of Ballistic Range which can easily simulate a flying projectile. The present Ballistic Range consists of piston, pump tube, highpressure tube, shock tube and launch tube. One-dimensional, unsteady compressible equations are solved to obtain the major design parameters of the present Ballistic Range.
A Theoretical Study of Shock tube Effect on the Ballistic Range Performance
G. Rajesh,J. M. Lee(이정민),H. D. Kim(김희동) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
The ballistic range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile aerodynamics and aeroballistics, since it can create an extremely high-pressure state in a very short time. Since the operation of the ballistic range involves many complicated gas dynamic processes, optimization of various design parameters of the ballistic range is important for the durability of its components. In the present study, a theoretical analysis has been made to investigate various unsteady processes involved in the operation of the ballistic range. The results obtained are validated with the available experimental data. The effect of adding a shock tube in between the pump tube and launch tube on the performance of the ballistic range is studied. A significant performance enhancement is obtained in the ballistic range with shock tube.
A Study of the Transient Flow Characteristics of a Vacuum Ejector-Diffuser System
G. Rajesh,H. D. Kim(김희동) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
In vacuum ejector-diffuser systems where a finite volume secondary chamber is used, the secondary jet exhibits transient characteristics during start-up. A steady state is achieved after some time in which mass entrainment prevails indefinitely inside the ejector, though there is no flow from the secondary chamber. An attempt is made in this work to study the infinite entrainment of secondary jet into the primary jet from a finite secondary chamber, with the help of a computational fluid dynamics method. The present study is also intended to identify the operating range of vacuum ejector-diffuser systems where the steady flow assumption can be applied without uncertainty. The results obtained show that the only condition in which an infinite mass entrainment is possible is the generation of a re-circulation zone near the primary nozzle exit. The flow in the secondary chamber attains a state of dynamic equilibrium at this point. Steady flow assumption is valid only after this point.