• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.39 no.6
• /
• pp.477-483
• /
• 2015

Investigations into cavity flows have been conducted for noise and vibration problems that arise in cavity systems. Cavity systems have been applied in engineering devices and have undergone rapid development in the aerospace industry. Meanwhile, to the author's best knowledge, the cavity on a curved wall has been seldom studied. The present work is conducted to study the flow physics of a cavity mounted on a curved wall. Numerical analysis is performed to investigate the cavity flow. Two variables of sub- and supersonic cavity flows were considered: the radius of curvature of the curved wall (L/R) and the inlet Mach number. The results show that the uniform vortex generated by the cavity flow on the curved wall stabilize the pressure fluctuation as time passes. As the inlet Mach number increases, the pressure fluctuation amplitude increases. The results obtained from the curved wall are compared with those from a straight wall using Rossiter's formula. The Strouhal number of the curved wall is lower than that of the straight wall. Lower Strouhal numbers have been obtained in the present computational fluid dynamics (CFD) results than in the theoretical results using Rossiter's formula.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2000.11a
• /
• pp.36-36
• /
• 2000

천음속 또는 초음속 유동이 유동장의 하류에서 부여되는 압력조건에 의하여 감속되는 경우나, 유동방향의 갑작스런 변화를 요구하는 물체 혹은 벽면이 존재하는 경우에 발생한 충격파는 벽면을 따라 발생하는 층류 혹은 난류 경계층과 복잡한 상호간섭 (interaction)을 일으켜 충격파에 의한 박리 발생, 충격파 하류에 새로운 충격파 발생, 충격파가 큰 진폭으로 진동하게 되는 현상 등을 발생시킨다. 이러한 간섭현상은 고속유동이 통과하는 유체요소나 유체기기의 성능을 좌우하는 매우 중요한 유동현상으로, 유체기계의 설계 시 사전에 고려되어야 할 중요한 공학적 문제이다.(중략)

• Journal of the Korean Society of Propulsion Engineers
• /
• v.9 no.2
• /
• pp.70-77
• /
• 2005

An axisymmetric supersonic ejector equipped with a converging-diverging diffuser was built and pressure at various locations along the ejector-diffuser system was recorded with emphasis on the supersonic starting of the secondary flow. In order to find the effects of the opening size of the secondary flow, a number of openings were used with a constant primary pressure. Supersonic starting was possible only for d/D, the ratio of the opening diameter and the diffuser throat diameter, less than 0.306. for larger values of d/D, the ejection begins at subsonic secondary flow condition. With the closure of the opening, the primary flow brings the normal shock downstream of the converging-diverging diffuser And the starting of the ejector continues even after the closure was removed.

• The KSFM Journal of Fluid Machinery
• /
• v.14 no.1
• /
• pp.55-60
• /
• 2011

Numerical analyses of a turbine redesigned to achieving the weight reduction by equipping square nozzles and the original turbine have been conducted and the results have been compared. The results show that the turbine with square section nozzles has more even flow distribution at the first row rotor inlet and less inactive areas but the loss induced by wake is increased. Despite the wake loss, the newly designed turbine shows better performance than the original one. It has also been found that the turbine performance can be improved by reshaping its stator and second row rotor.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2001.04a
• /
• pp.35-38
• /
• 2001

The aerothermodynamic characteristics of SCRamjet engine for the airbreathing populsion system of the next generation flight vehicle are described. As the flow is passing by, combustion caused the total pressure loss and the Mach number decrease, but nozzle exit velocity is large enough to produce net thrust. To simulate supersonic combustion test, preliminary design of ground-based blowdown type supersonic combustion tunnel is attained. Minimum allowable operating pressure and mass flow rate are calculated for the design Mach number of 2.5 at the test section of a supersonic combustion tunnel.

• Proceedings of the KSME Conference
• /
• 2000.04b
• /
• pp.525-530
• /
• 2000

The effects of vortex generators, in the form of small tabs projecting into the flow at the axisymmetric supersonic nozzle exit and triangular thin tapes attached on the inner surface at the nozzle exit, on the characterixtics of supersonic mixing enhancements are experimentally investigated. Delta-shaped tabs as small as 1% of the nozzle exit area produce strong counter-rotating vortices, and is found to produce significant effects on the jet flowfield downstream of the nozzle. The effects is larger on the under-expanded cases than over- and perfect-expanded cases. Nozzle inner surface roughness also can do a role of centerline pressure decay for highly under-expanded jet cases. The effects of the angle of tabs with respect to flow direction are also investigated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 1994.04a
• /
• pp.39-45
• /
• 1994

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2002.10a
• /
• pp.48-48
• /
• 2002

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2002.10a
• /
• pp.49-52
• /
• 2002

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2001.11a
• /
• pp.85-86
• /
• 2001