Numerical Simulation of Shock Wave Propagation in Ducts with Grooves

The pressure attenuation of moving shocks when they propagate in ducts, is of great importance in a wide variety of applications, such as health, safety, and transportation. The objective of this research is to simulate the propagation of shock waves in ducts with roughness. The roughness is added in the form of grooves as in an existing experiment. Different shapes are considered in order to better understand the physics behind the evolution of the complex shock patterns resulting from diffraction, reflection and refraction of the primary moving shock. The contribution of grooves and duct shape on these phenomena and pressure attenuation is investigated. The numerical method is validated through several test cases, and the results are compared against the theory and the experimental measurements. Good agreement between high resolution computations and the experiment is obtained for the shock speeds and complex wave patterns created by the grooves. Time histories of pressure at various locations are also compared. It is found that accurate pressure history agreement requires a close representation of the full experimental setup to fully capture boundary layer development, and pressure losses associated with unsteady moving shocks in long ducts. Different groove geometries have been tested in the numerical computation in order to identify the shape that will diminish shock strength, hence pressure extrema more effectively. Analysis and animations of the computed results are employed to reveal salient features of the unsteady flowfield

Vorticity production in shock diffraction

科研費報告書収録論文(課題番号:14205138/研究代表者:中橋和博/音速近くの流れの解明と制御

Aeronautical engineering: A continuing bibliography with indexes (supplement 225)

This bibliography lists 429 reports, articles, and other documents introduced into the NASA scientific and technical information system in March, 1988

Aeronautical engineering: A continuing bibliography with indexes (supplement 237)

This bibliography lists 572 reports, articles, and other documents introduced into the NASA scientific and technical information system in February, 1989. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Unsteady three-dimensional compressible vortex flows

Vortex flows are fundamental to nature and technology. In this dissertation, the results of an experimental and numerical investigation into the behaviour of the free vortex generated by shock diffraction over edges yawed to the incident shock wave are presented. The objectives of this study were to explore the behaviour of the free vortex in three dimensions, with a particular focus on the distortions caused to the vortex by the presence of a solid boundary, or wall. Threedimensional numerical simulations and experimentally obtained schlieren photographs reveal significant distortion and bending of the free vortex in regions near the boundary of the flow domain, so as to meet it at a right angle. Experimentation was performed in a shock tube for incident shock Mach numbers of 1.32, 1.42, and 1.65, with four test models, two incorporating straight diffraction edges, and two incorporating curved diffracting edges. Numerical simulation was performed with Fluent 6.3.26 software. The numerical solutions were validated against the experimental results through pictorial comparison, and despite relatively coarse meshes being used, were found to mimic the experimental results very well. The numerical results are used here to investigate and explain the various features of the resultant flow fields, with particular emphasis placed on the behaviour and properties of the free vortex. The effects of bending on the structure of the vortex and on the flow properties with the vortex are examined. The rate of circulation production for the three-dimensional diffraction cases was calculated, and the trends observed correlated with those for the much published two-dimensional diffraction case. Also investigated is the three-dimensional shock diffraction case, where it was found that the shape of the diffracted shock wave differed slightly from the two-dimensional case in the region near the boundaries of the domain

Aeronautical engineering: A continuing bibliography with indexes (supplement 266)

This bibliography lists 645 reports, articles, and other documents introduced into the NASA scientific and technical information system in May 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Aeronautical engineering: A continuing bibliography with indexes (supplement 210)

This bibliography lists 409 reports, articles and other documents introduced into the NASA scientific and technical information system in January 1987

Spectroscopic Measurements in the Shock Relaxation Region of a Hypervelocity Mach Reflection

We examine the spatial temperature profile in the non-equilibrium relaxation region behind a stationary shock wave. The normal shock wave is established through a Mach reflection configuration from an opposing wedge arrangement for a hypervelocity air Mach 7.42 freestream. Schlieren images confirm that the shock configuration is steady and the location is repeatable. Emission spectroscopy is used to identify dissociated species and to obtain vibrational temperature measurements using the NO and OH A-X band sequences. Temperature measurements are presented at selected locations behind the normal shock. LIFBASE is used as the simulation spectrum software for OH temperature-fitting, however the need to access higher vibrational and rotational levels for NO leads to the use of an in-house developed algorithm. For NO, results demonstrate the contribution of higher vibrational and rotational levels to the spectra at the conditions of this study. Very good agreement is achieved between the experimentally measured NO vibrational temperatures and calculations performed using a state-resolved, one-dimensional forced harmonic oscillator thermochemical model