The Experts below are selected from a list of 213 Experts worldwide ranked by ideXlab platform
Zonglin Jiang - One of the best experts on this subject based on the ideXlab platform.
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A theoretical and computational study of the vibration excitation on the transition criteria of Shock wave reflections
Aerospace Science and Technology, 2019Co-Authors: Jun Peng, Zongmin Hu, Zijian Zhang, Zonglin JiangAbstract:Abstract In this paper, we study the vibration excitation on the reflection of Shock waves in hypersonic flows by using analytical and computational approaches. First, a theoretical approach is established to solve the Shock relations which are further applied to develop the Shock Polar analytical method for high-temperature air. Then, a comparative investigation using calorically perfect gas model and thermally perfect gas model considering vibration excitation indicates an obvious change to the overall profile of the Shock Polar. The post-Shock pressure increases within the strong branch of the Shock Polar while decreases within the weak branch due to vibration excitation of air molecules. A more notable phenomenon is the increase in the maximum deflection angle of the Shock Polar which can significantly influence the detachment criterion of Shock reflection transition in high-temperature air flows. The Shock Polar analysis of Shock reflection shows that the vibration excitation result in an obvious increase to the detachment criterion while a slight increase to the von Neumann criterion. A series of computations are conducted to confirm the above analytical findings on the Shock reflection considering the vibration excitation. A slight difference of transition criterion between the theory and computations is found to be caused by the existence of the expansion fan which is an inherent flow structure. The proposed Shock Polar analytical method is proved to be an effective but simple approach for the study of Shock wave reflections in hypersonic flows.
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Three-dimensional Shock wave configurations induced by two asymmetrical intersecting wedges in supersonic flow
Shock Waves, 2017Co-Authors: Gaoxiang Xiang, Chun Wang, Honghui Teng, Zonglin JiangAbstract:This study explores the three-dimensional (3D) wave configurations induced by 3D asymmetrical intersecting compression wedges in supersonic and hypersonic inviscid flows. By using the “spatial dimension reduction” approach, the problem of 3D steady Shock/Shock interaction is converted to that of the interaction of two moving Shock waves in the characteristic two-dimensional (2D) plane. Shock Polar theory is used to analyze the Shock configurations in asymmetrical situations. The results show that various Shock configurations exist in 3D asymmetrical Shock wave interactions, including regular interaction, transitioned regular interaction, single Mach interaction, inverse single Mach interaction, transitional double Mach interaction, weak Shock interaction, and weak single Mach interaction. All of the above 3D steady Shock/Shock interactions have their corresponding 2D moving Shock/Shock interaction configurations. Numerical simulations are performed by solving the 3D inviscid Euler equations with the non-oscillatory, non-free parameters, dissipative (NND) numerical scheme, and good agreement with the theoretical analysis is obtained. Furthermore, the comparison of results show that the concept of the “virtual wall” in Shock dynamics theory is helpful for understanding the mechanism of two-dimensional Shock/Shock interactions.
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Study on Mach stems induced by interaction of planar Shock waves on two intersecting wedges
Acta Mechanica Sinica, 2015Co-Authors: Gaoxiang Xiang, Chun Wang, Honghui Teng, Yang Yang, Zonglin JiangAbstract:The properties of Mach stems in hypersonic corner flow induced by Mach interaction over 3D intersecting wedges were studied theoretically and numerically. A new method called "spatial dimension reduction" was used to analyze theoretically the location and Mach number behind Mach stems. By using this approach, the problem of 3D steady Shock/Shock interaction over 3D intersecting wedges was transformed into a 2D moving one on cross sections, which can be solved by Shock-Polar theory and Shock dynamics theory. The properties of Mach interaction over 3D intersecting wedges can be analyzed with the new method, including pressure, temperature, density in the vicinity of triple points, location, and Mach number behind Mach stems. Theoretical results were compared with numerical results, and good agreement was obtained. Also, the influence of Mach number and wedge angle on the properties of a 3D Mach stem was studied.
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On the transition pattern of the oblique detonation structure
Journal of Fluid Mechanics, 2012Co-Authors: Honghui Teng, Zonglin JiangAbstract:Oblique detonation waves are simulated to study the evolution of their morphology as gasdynamic and chemical parameters are varied. Although two kinds of transition pattern have previously been observed, specifically an abrupt transition and a smooth one, the determining factors for the transition pattern are still unclear. Numerical results show that the transition pattern is influenced by the inflow Mach number, chemical activation energy and heat release. Despite the fact that these parameters were known to influence the detonation instability, the transition pattern variation cannot be predicted according to the instability criterion. In this study, the difference in the oblique Shock and detonation angles is proposed as the criterion to determine the transition pattern with the aid of Shock-Polar analysis. It is found that the smooth transition will appear when the angle difference is small, while the abrupt transition will occur when the difference is large. The shift from the smooth transition to the abrupt transition occurs when the angle difference is about 15 degrees-18 degrees. The previously proposed criterion using the characteristic time ratio is also examined and compared with the present angle difference criterion, and the latter is proved to provide better results.
Ravi Samtaney - One of the best experts on this subject based on the ideXlab platform.
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Planar Shock cylindrical focusing by a perfect-gas lens
Physics of Fluids, 2006Co-Authors: P. E. Dimotakis, Ravi SamtaneyAbstract:We document a gas lensing technique that generates a converging Shock wave in a two-dimensional wedge geometry. A successful design must satisfy three criteria at the contact point between the gas lens and the wedge leading edge to minimize nonlinear reflected and other wave effects. The result is a single-point solution in a multidimensional parameter space. The gas lens shape is computed using Shock-Polar analysis for regular refraction of the incident Shock at the gas lens interface. For the range of parameters investigated, the required gas-lens interface is closely matched by an ellipse or hyperbola. Nonlinear Euler simulations confirm the analysis and that the transmitted Shock is circular. As the converging transmitted Shock propagates down the wedge, its shape remains nearly uniform with less than 0.1% peak departures from a perfect circular cylinder segment. Departure from the design criteria leads to converging Shocks that depart from the required shape. The sensitivity to incident Shock Mach number, as well as the qualitative effects of the presence of boundary layers are also discussed.
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on Shock Polar analysis and analytical expressions for vorticity deposition in Shock accelerated density stratified interfaces
Physics of Fluids, 1993Co-Authors: Ravi Samtaney, Norman J. ZabuskyAbstract:Vorticity is deposited due to baroclinic effects on the surface of a density‐stratified interface accelerated by a Shock. An analytical expression is presented, derived from Shock Polar analysis, for circulation per unit length on a fast–slow planar density interface inclined at an angle to the incident Shock. The analytical expression is integrated to yield total circulation on nonplanar interfaces (sinusoidal and semicircular interfaces) accelerated by Shocks. The analytical results agree well with diagnostics from numerical experiments using a second‐order Godunov code for the Euler equations.
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On Shock Polar analysis and analytical expressions for vorticity deposition in Shock‐accelerated density‐stratified interfaces
Physics of Fluids A: Fluid Dynamics, 1993Co-Authors: Ravi Samtaney, Norman J. ZabuskyAbstract:Vorticity is deposited due to baroclinic effects on the surface of a density‐stratified interface accelerated by a Shock. An analytical expression is presented, derived from Shock Polar analysis, for circulation per unit length on a fast–slow planar density interface inclined at an angle to the incident Shock. The analytical expression is integrated to yield total circulation on nonplanar interfaces (sinusoidal and semicircular interfaces) accelerated by Shocks. The analytical results agree well with diagnostics from numerical experiments using a second‐order Godunov code for the Euler equations.
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Vorticity generation and evolution in Shock‐accelerated density‐stratified interfaces
Physics of Fluids A: Fluid Dynamics, 1992Co-Authors: Xiaolong Yang, Ravi Samtaney, Norman J. Zabusky, I-liang Chern, John F. HawleyAbstract:The results of direct numerical simulations of inviscid planar Shock‐accelerated density‐stratified interfaces in two dimensions are presented and compared with Shock tube experiments of Haas [(private communication, 1988)] and Sturtevant [in Shock Tubes and Waves, edited by H. Gronig (VCH, Berlin, 1987), p. 89] . Heavy‐to‐light (‘‘slow/fast or s/f) and light‐to‐heavy (‘‘fast/slow,’’ or f/s) gas interfaces are examined and early‐time impulsive vorticity deposition and the evolution of coherent vortex structures are emphasized and quantified. The present second‐order Godunov scheme yields excellent agreement with Shock‐Polar analyses at early time. A more physical vortex interpretation explains the commonly used (i.e., linear paradigm) designations of ‘‘unstable’’ and ‘‘stable’’ for the f/s and s/f interfaces, respectively. The later time events are Rayleigh–Taylor like and can be described in terms of the evolution of a vortex layer (large‐scale translation and rotation): asymmetric tip vortex ‘‘roll‐up’’...
Xisheng Luo - One of the best experts on this subject based on the ideXlab platform.
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RR-MR transition of a Type V Shock interaction in inviscid double-wedge flow with high-temperature gas effects
Shock Waves, 2017Co-Authors: W. Xiong, Yujian Zhu, Xisheng LuoAbstract:The transition between regular reflection (RR) and Mach reflection (MR) of a Type V Shock–Shock interaction on a double-wedge geometry with non-equilibrium high-temperature gas effects is investigated theoretically and numerically. A modified Shock Polar method that involves thermochemical non-equilibrium processes is applied to calculate the theoretical critical angles of transition based on the detachment criterion and the von Neumann criterion. Two-dimensional inviscid numerical simulations are performed correspondingly to reveal the interactive wave patterns, the transition processes, and the critical transition angles. The theoretical and numerical results of the critical transition angles are compared, which shows evident disagreement, indicating that the transition mechanism between RR and MR of a Type V Shock interaction is beyond the admissible scope of the classical theory. Numerical results show that the collisions of triple points of the Type V interaction cause the transition instead. Compared with the frozen counterpart, it is found that the high-temperature gas effects lead to a larger critical transition angle and a larger hysteresis interval.
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On transition of type V interaction in double-wedge flow with non-equilibrium effects
Theoretical and Applied Mechanics Letters, 2016Co-Authors: W. Xiong, Yujian Zhu, Xisheng LuoAbstract:Abstract The transition between regular reflection (RR) and Mach reflection (MR) of type V Shock–Shock interaction on a double-wedge geometry with high temperature non-equilibrium effects is investigated by extended Shock-Polar method and numerical simulation. First, the critical angles of transition from detachment criterion and von Neumann criterion are determined by the extended Shock-Polar method considering the non-equilibrium effects. Then wave patterns and the transition process are numerically obtained. Results of the critical transition angles from Shock-Polar calculation and numerical simulation show evident disagreement, indicating transition mechanism between RR and MR of type V interaction is changed. By comparing with the frozen counterpart, it is also found that non-equilibrium effects lead to a larger critical wedge angle and a larger hysteresis interval.
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On Type VI–V transition in hypersonic double-wedge flows with thermo-chemical non-equilibrium effects
Physics of Fluids, 2014Co-Authors: Yujian Zhu, Xisheng LuoAbstract:The transition from Type VI to V of inviscid Shock interactions on a double-wedge geometry is investigated theoretically and numerically for hypersonic non-equilibrium gas flows. The Shock Polar method valid for the non-equilibrium gas is developed by introducing a non-equilibrium relaxation length. A preliminary rule for choosing the suitable non-equilibrium relaxation length in different regions of the double-wedge flow is proposed by analyzing the relaxing characteristics. Following this proposal, the Shock Polar method valid for the non-equilibrium gas can be easily applied to other hypersonic Shock interactions. Numerical simulation is used to capture the complete transition from Type VI to V and to obtain the second wedge angle span for this process. The comparison between the theory and the computation indicates that the Shock Polar method for the non-equilibrium gas can well predict the regional pressure and the critical angle. It is found that the non-equilibrium gas effects lead to a larger seco...
Norman J. Zabusky - One of the best experts on this subject based on the ideXlab platform.
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on Shock Polar analysis and analytical expressions for vorticity deposition in Shock accelerated density stratified interfaces
Physics of Fluids, 1993Co-Authors: Ravi Samtaney, Norman J. ZabuskyAbstract:Vorticity is deposited due to baroclinic effects on the surface of a density‐stratified interface accelerated by a Shock. An analytical expression is presented, derived from Shock Polar analysis, for circulation per unit length on a fast–slow planar density interface inclined at an angle to the incident Shock. The analytical expression is integrated to yield total circulation on nonplanar interfaces (sinusoidal and semicircular interfaces) accelerated by Shocks. The analytical results agree well with diagnostics from numerical experiments using a second‐order Godunov code for the Euler equations.
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On Shock Polar analysis and analytical expressions for vorticity deposition in Shock‐accelerated density‐stratified interfaces
Physics of Fluids A: Fluid Dynamics, 1993Co-Authors: Ravi Samtaney, Norman J. ZabuskyAbstract:Vorticity is deposited due to baroclinic effects on the surface of a density‐stratified interface accelerated by a Shock. An analytical expression is presented, derived from Shock Polar analysis, for circulation per unit length on a fast–slow planar density interface inclined at an angle to the incident Shock. The analytical expression is integrated to yield total circulation on nonplanar interfaces (sinusoidal and semicircular interfaces) accelerated by Shocks. The analytical results agree well with diagnostics from numerical experiments using a second‐order Godunov code for the Euler equations.
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Vorticity generation and evolution in Shock‐accelerated density‐stratified interfaces
Physics of Fluids A: Fluid Dynamics, 1992Co-Authors: Xiaolong Yang, Ravi Samtaney, Norman J. Zabusky, I-liang Chern, John F. HawleyAbstract:The results of direct numerical simulations of inviscid planar Shock‐accelerated density‐stratified interfaces in two dimensions are presented and compared with Shock tube experiments of Haas [(private communication, 1988)] and Sturtevant [in Shock Tubes and Waves, edited by H. Gronig (VCH, Berlin, 1987), p. 89] . Heavy‐to‐light (‘‘slow/fast or s/f) and light‐to‐heavy (‘‘fast/slow,’’ or f/s) gas interfaces are examined and early‐time impulsive vorticity deposition and the evolution of coherent vortex structures are emphasized and quantified. The present second‐order Godunov scheme yields excellent agreement with Shock‐Polar analyses at early time. A more physical vortex interpretation explains the commonly used (i.e., linear paradigm) designations of ‘‘unstable’’ and ‘‘stable’’ for the f/s and s/f interfaces, respectively. The later time events are Rayleigh–Taylor like and can be described in terms of the evolution of a vortex layer (large‐scale translation and rotation): asymmetric tip vortex ‘‘roll‐up’’...
Yujian Zhu - One of the best experts on this subject based on the ideXlab platform.
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RR-MR transition of a Type V Shock interaction in inviscid double-wedge flow with high-temperature gas effects
Shock Waves, 2017Co-Authors: W. Xiong, Yujian Zhu, Xisheng LuoAbstract:The transition between regular reflection (RR) and Mach reflection (MR) of a Type V Shock–Shock interaction on a double-wedge geometry with non-equilibrium high-temperature gas effects is investigated theoretically and numerically. A modified Shock Polar method that involves thermochemical non-equilibrium processes is applied to calculate the theoretical critical angles of transition based on the detachment criterion and the von Neumann criterion. Two-dimensional inviscid numerical simulations are performed correspondingly to reveal the interactive wave patterns, the transition processes, and the critical transition angles. The theoretical and numerical results of the critical transition angles are compared, which shows evident disagreement, indicating that the transition mechanism between RR and MR of a Type V Shock interaction is beyond the admissible scope of the classical theory. Numerical results show that the collisions of triple points of the Type V interaction cause the transition instead. Compared with the frozen counterpart, it is found that the high-temperature gas effects lead to a larger critical transition angle and a larger hysteresis interval.
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On transition of type V interaction in double-wedge flow with non-equilibrium effects
Theoretical and Applied Mechanics Letters, 2016Co-Authors: W. Xiong, Yujian Zhu, Xisheng LuoAbstract:Abstract The transition between regular reflection (RR) and Mach reflection (MR) of type V Shock–Shock interaction on a double-wedge geometry with high temperature non-equilibrium effects is investigated by extended Shock-Polar method and numerical simulation. First, the critical angles of transition from detachment criterion and von Neumann criterion are determined by the extended Shock-Polar method considering the non-equilibrium effects. Then wave patterns and the transition process are numerically obtained. Results of the critical transition angles from Shock-Polar calculation and numerical simulation show evident disagreement, indicating transition mechanism between RR and MR of type V interaction is changed. By comparing with the frozen counterpart, it is also found that non-equilibrium effects lead to a larger critical wedge angle and a larger hysteresis interval.
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On Type VI–V transition in hypersonic double-wedge flows with thermo-chemical non-equilibrium effects
Physics of Fluids, 2014Co-Authors: Yujian Zhu, Xisheng LuoAbstract:The transition from Type VI to V of inviscid Shock interactions on a double-wedge geometry is investigated theoretically and numerically for hypersonic non-equilibrium gas flows. The Shock Polar method valid for the non-equilibrium gas is developed by introducing a non-equilibrium relaxation length. A preliminary rule for choosing the suitable non-equilibrium relaxation length in different regions of the double-wedge flow is proposed by analyzing the relaxing characteristics. Following this proposal, the Shock Polar method valid for the non-equilibrium gas can be easily applied to other hypersonic Shock interactions. Numerical simulation is used to capture the complete transition from Type VI to V and to obtain the second wedge angle span for this process. The comparison between the theory and the computation indicates that the Shock Polar method for the non-equilibrium gas can well predict the regional pressure and the critical angle. It is found that the non-equilibrium gas effects lead to a larger seco...
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Planar Shock-cylindrical blast wave interaction
Shock Waves, 2005Co-Authors: X. L. Yang, Yujian Zhu, Jiming Yang, Mingyu Sun, Kazuyoshi TakayamaAbstract:The phenomena of interaction between planar Shock wave and cylindrical blast wave is studied theoretically and numerically. Our work concentrated on the case of a blast source ignited in front of a planar moving Shock. The method of dimensional analysis is first applied to serve as a foundation for numerical simulation. Then some features of the flow field, especially the transition of the waves system, are analyzed through theory of Shock Polar. The results of theoretical analysis are agreeable to numerical results.