scholarly journals Numerical Study of Disturbance Resistance of Oblique Detonation Waves

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Yu Liu ◽  
Baoguo Xiao ◽  
Lan Wang ◽  
Chao Wang
Keyword(s):  
Shock Wave ◽  
High Speed ◽  
Numerical Study ◽  
Fundamental Problem ◽  
Wedge Angle ◽  
Oblique Shock Wave ◽  
Detonation Waves ◽  
Wave Surface ◽  
Flow Disturbances ◽  
Triple Points

The stability of oblique detonation waves (ODWs) is a fundamental problem, and resistance of ODWs against disturbances is crucial for oblique detonation engines in high-speed propulsion. In this work, numerical studies on ODW stability in disturbed flows are conducted using the two-dimensional reactive Euler equations with a two-step induction-reaction kinetic model. Two kinds of flow disturbances are, respectively, introduced into the steady flow field to assess ODW stability, including upstream transient high-pressure disturbance (UTHD) and downstream jet flow disturbance (DJFD) with different durations. Generally, an ODW is susceptible to disturbances at larger wedge angles and stable at smaller wedge angles. In the unstable wedge angle range, different ODW structures and transition patterns are obtained after disturbances, including different locations of the primary triple points, different numbers of the steady triple points on the wave surface, and different transition patterns from the leading oblique shock wave to the ODW. It is found that the primary triple point tends to move upstream for the disturbances that can form a local strong detached bow shock wave near the wedge tip. In contrast, the wave surface and the transition pattern are susceptible to all of the disturbances introduced in this study. Despite the unstable responses of the ODWs to the disturbances, the ODWs can keep standing stability after disturbances, which is beneficial to the propulsion application of ODWs.

scholarly journals A numerical study of oblique shock-wave reflections with experimental comparisons

1985 ◽  
Vol 398 (1814) ◽  
pp. 117-140 ◽  
Keyword(s):  
Shock Wave ◽  
Numerical Study ◽  
Wedge Angle ◽  
Quantitative Agreement ◽  
Oblique Shock ◽  
Computational Method ◽  
Oblique Shock Wave ◽  
Wave Reflections ◽  
Inviscid Flows ◽  
Reflection Transition

A direct comparison is made for several occurrences of oblique shock-wave reflections between interferometric results obtained at the University of Toronto Institute for Aerospace Studies (UTIAS) 10 cm x 18 cm hyper­-velocity shock tube and numerical results obtained by using a current computational method for solving the Euler equations. Very good qualitative agreement is obtained for equilibrium and frozen flow fields except in small regions where the experiments were dominated by viscous flow. The quantitative agreement is very close in some cases but can be out by 10–15% in cases with non-equilibrium flow or viscous structures or both. Additional parametrized sequences of calculations are presented to assess the utility of the present numerical method in constructing the various reflection–transition lines for perfect inviscid flows in the shock-wave Mach number, wedge-angle ( M s , θ w )-plane, and the validity of the ‘boundary-layer defect’ theory.

scholarly journals Отрицательное маховское отражение с множественными тройными конфигурациями при дифракции ударной волны на клине

2021 ◽  
Vol 47 (20) ◽  
pp. 11
Author(s):  
П.Ю. Георгиевский ◽  
А.Н. Максимов ◽  
В.П. Фокеев
Keyword(s):  
Shock Wave ◽  
Euler Equations ◽  
Numerical Study ◽  
Mach Reflection ◽  
Wedge Angle ◽  
Regular Reflection ◽  
Self Similar

Within the framework of the Euler equations, a numerical study of the structure of a self-similar flow for various types of negative Mach reflection during diffraction of a shock wave by a wedge is performed. Along with the known modes of double and triple Mach reflection, a qualitatively new mode of negative Mach reflection with multiple three-shock configurations is observed. Peculiarities of the transition from multiple Mach reflection to regular reflection when changing the wedge angle are noted.

Numerical Study on Shock Wave Propagation with Obstacles during Methane Explosion

2010 ◽  
Vol 33 ◽  
pp. 114-118 ◽  
Author(s):  
Zhi Ming Qu
Keyword(s):  
Shock Wave ◽  
Wave Propagation ◽  
Velocity Gradient ◽  
High Speed ◽  
Numerical Study ◽  
Shock Wave Propagation ◽  
Gradient Field ◽  
Shock Propagation ◽  
Mixture Flow ◽  
Methane Mixture

During shock wave propagation in the pipeline, the flow field of speed, pressure and temperature is evenly distributed. If there are obstacles, then the flow will be changed while the velocity gradient is formed near the obstacles. Passing through the obstacles, a high-speed gradient of the unburned methane mixture flow is established. While reaching the obstacle, the shock wave surface is rapidly stretched to increase the significant transmission speed. Propagating in the gradient field, the shock wave will be stretched and folded. The deformation of shock wave causes consumption of fuel and oxygen in greater unburned methane surface, which results in heat release rate increasing and faster shock propagation. In conclusion, shock wave causes larger advection speed in front of the unburned methane mixture, increasing flow velocity gradient further and leading to more intense shock wave propagation.

A numerical study of oblique shock wave reflections over wedges in an ideal quantum gas

Shock Waves ◽  
2008 ◽  
Vol 18 (3) ◽  
pp. 193-204 ◽  
Author(s):  
J. C. Huang ◽  
T. Y. Hsieh ◽  
J. Y. Yang ◽  
K. Takayama
Keyword(s):  
Shock Wave ◽  
Numerical Study ◽  
Oblique Shock ◽  
Oblique Shock Wave ◽  
Quantum Gas ◽  
Wave Reflections ◽  
Ideal Quantum

scholarly journals Experimental Study on Shock Wave Propagation of the Explosion in a Pipe with Holes by High-Speed Schlieren Method

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Gang Zhang
Keyword(s):  
Shock Wave ◽  
Wave Propagation ◽  
High Speed ◽  
Experimental System ◽  
Test System ◽  
Shock Wave Propagation ◽  
Oblique Shock Wave ◽  
Schlieren Method ◽  
Wave Fronts ◽  
Blast Energy

The shock wave propagation of the explosion in a pipe with holes was studied by a high-speed schlieren experimental system. In the experiments, schlieren images in the explosion were recorded by a high-speed camera from parallel and perpendicular orientations, respectively, and the pressure in the air was measured by an overpressure test system. In parallel orientation, it is observed that the steel pipe blocks the propagation of blast gases, but it allows the propagation of shock waves with a symmetrical shape. In perpendicular orientation, oblique shock wave fronts were observed, indicating the propagation of explosion detonation along the charge. Shock wave velocity in the hole direction is larger than that in the nonhole direction, indicating the function of holes in controlling blast energy, that is, leading blast energy to hole direction. Furthermore, the function of holes is verified by overpressure measurements in which peak overpressure in the hole direction is 0.87 KPa, 2.8 times larger than that in the nonhole direction. Finally, the variation of pressure around the explosion in a pipe with holes was analyzed by numerical simulation, qualitatively agreeing with high-speed schlieren experiments.

Evaluation of assumptions and criteria in pseudostationary oblique shock-wave reflections

1986 ◽  
Vol 406 (1830) ◽  
pp. 75-92 ◽  
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Mach Reflection ◽  
Wedge Angle ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Oblique Shock ◽  
Oblique Shock Wave ◽  
Reflected Shock ◽  
Wedge Surface

Many experiments in various gases have now been performed on regular and Mach reflection of oblique shock waves in pseudostationary flow. Experimental agreement with the analytical boundaries for such reflec­tions with two- and three-shock theories is reasonable but not precise enough over the entire range of incident shock-wave Mach numbers ( M s ) and compression wedge angle ( θ W ) used in the experiments. In order to improve the agreement, the assumptions and criteria employed in the analysis were critically examined by the use of the experimental data for nitrogen (N 2 ), argon (Ar), carbon-dioxide (CO 2 ), air and sulphurhexa-fluoride (SF 6 ). The assumptions regarding the excitation of the internal degrees of freedom were evaluated based on a relation between the relaxation lengths and a characteristic length of the flow. The ranges in which the frozen-gas and vibrational-equilibrium-gas assumptions can be applied were verified by comparing the experimental and numerical values of δ, the angle between the incident and the reflected shock waves. The deviations of the experimental orientation of the Mach stem at the triple point from a line perpendicular to the wedge surface were considered. A new criterion for the transition from single-Mach to complex-Mach reflection improved the agreement with experiments in the ( M S , θ W )-transition-boundary map. The effects of the shock-induced boundary layer on the wedge surface on the reflected-wave angle and the persistence of regular reflection into the Mach reflection region (‘von Neumann paradox’) were evaluated.

scholarly journals Numerical study of wedge-induced oblique detonations in unsteady flow

2019 ◽  
Vol 876 ◽  
pp. 264-287 ◽  
Author(s):  
Pengfei Yang ◽  
Hoi Dick Ng ◽  
Honghui Teng
Keyword(s):  
Unsteady Flow ◽  
Numerical Study ◽  
Single Pulse ◽  
Smooth Transition ◽  
Detonation Waves ◽  
Hypersonic Propulsion ◽  
Flow Parameters ◽  
Front Position ◽  
Reactive Euler Equations ◽  
Triple Points

Oblique detonation waves (ODWs) have been studied widely to facilitate their employment in hypersonic propulsion, but the effects of continuous unsteady inflow have never been addressed so far. Thus, the present study investigates wedge-induced oblique detonations in unsteady flow via numerical simulations based on the reactive Euler equations with a two-step induction–reaction kinetic model. As a first step, the chemical and flow parameters are chosen for the simplest structure such that the ODW initiation occurs under a smooth transition with a curved shock. After a steady ODW with smooth initiation transition is established, the inflow is then subject to a continuous sinusoidal density/temperature disturbance. Cases with single-pulse inflow variation are also simulated to clarify whether the observed phenomena are derived solely from the continuous disturbance. Two aspects are analysed to investigate the features of ODWs in unsteady flow, namely, the formation of triple points on the surface, and the movement of the reactive front position. On the formation of triple points, the continuous disturbance generates at most one pair of triple points, less than or equal to the number of triple points in single-pulse cases. This indicates that the effects of continuous disturbance weaken the ability to generate the triple points, although there appear more triple points convected downstream on the surface at any given instant. On the movement of the reactive front, oscillatory behaviours are induced in either single-pulse or continuous disturbance cases. However, more complicated dynamic displacements and noticeable effects of unsteadiness are observed in the cases of continuous disturbance, and are found to be sensitive to the disturbance wavenumber, $N$. Increasing $N$ results in three regimes with distinct behaviours, which are quasi-steady, overshooting oscillation and unstable ODW. For the quasi-steady case with low $N$, the reactive front oscillates coherently with the inflow disturbance with slightly higher amplitude around the initiation region. The overshooting oscillation generates the most significant variation of downstream surface in the case of modest $N$, reflecting a resonance-like behaviour of unsteady ODW. In the case of high $N$, the disturbed ODW surface readjusts itself with local unstable features. It becomes more robust and the reactive front of the final unstable ODW structure is less susceptible to flow disturbance.

The interaction of an oblique shock wave with a laminar boundary layer revisited. An experimental and numerical study

1987 ◽  
Vol 177 ◽  
pp. 247-263 ◽  
Author(s):  
G. Degrez ◽  
C. H. Boccadoro ◽  
J. F. Wendt
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Laminar Boundary Layer ◽  
Stokes Equations ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Oblique Shock ◽  
Oblique Shock Wave ◽  
Approximate Factorization ◽  
Pressure Distributions

An investigation of an oblique shock wave/laminar boundary layer interaction is presented. The Mach number was 2.15, the Reynolds number was 105 and the overall pressure ratio was 1.55. The interation has been demonstrated to be laminar and nominally two-dimensional. Experimental results include pressure distributions on the plate and single component laser-Doppler velocimetry velocity measurements both in the attached and separated regions.The numerical results have been obtained by solving the full compressible Navier-Stokes equations with the implicit approximate factorization algorithm by Beam & Warming (1980). Comparison with experimental data shows good agreement in terms of pressure distributions, positions of separation and reattachment and velocity profiles.

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