A mechanism of wave drag reduction in the thermal energy deposition experiments

Markhotok, A.

doi:10.1063/1.4922434

Cited by 12 publications

(30 citation statements)

References 34 publications

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“…where X i and Y i are the front coordinates and the angles γ i and φ i correspond to the same interaction point i. For the same "sphere-to-sphere" geometry considered in [22], the equations can be set for an interaction time t = nR b /V 1 , 0 < n < 2, scaled with a characteristic time τ =…”

Section: The Model Of Vortex Generationmentioning

confidence: 99%

“…The media on both sides of the interface are considered as ideal gases with initially equal pressures across the interface. At the second stage of the interaction, when the refracted shock wave starts to propagate off the interface through the plasma volume, the effect is dependent on the density distribution in the cloud [15,22,35] and will be considered separately for each type of the distribution. Even though the changes in the shock front shape start to appear during this period of time, they are still the consequences of the interaction at both stages, on the interface and in volume.…”

Section: The Model Of Vortex Generationmentioning

confidence: 99%

“…The initially spherical shock front is incident on the spherical/cylindrical interface with the horizontal constant speed V 1 , from left to right, center to center, and after the refraction continues to propagate in the non-uniform medium. This problem for the refracted shock parameters has been already solved in [22] using 2D model and the time dependent system of equations for the front's surface coordinates can be borrowed from there:…”

Section: B the Exponential Density Distribution Casementioning

confidence: 99%

“…Propagation of a shock through plasma with such a density distribution in the sphere-tosphere geometry has been studied in [22] and the derivations given below will be done for the same problem geometry and parameters used in the paper. The density is assumed as changing in the longitudinal direction only starting from the leftmost point on the interface.…”

Section: C Power-law Density Distribution Casementioning

confidence: 99%

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A mechanism of vortex generation in a supersonic flow behind a gas-plasma interface

Markhotok

2018

Fluid Dyn. Res.

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The origin of a vortex structure generated during the shock-plasma interaction is investigated. A two-dimensional model based on the shock refraction mechanism successfully unifies the vortex generation with major co-processes typical for the interaction and thus well fits in their cause-and-consequence relationship. Numerical simulations demonstrated the possibility of an intense vortex generation with a continuous positive dynamics as the shock crosses the interface. It was shown that while the vorticity is triggered by the shock refraction on the interface, it is the gas parameter distribution that distinctively determines the parameters of the vortex evolution. The proposed model also provides an insight into interesting aspects of the refraction effects for both, the shock wave and the flow behind it (double refraction). The results are applicable to the problems of energy deposition in a hypersonic flow, a flame-shock interaction, in combustion, in astrophysics, and in the fusion research.

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Section: The Model Of Vortex Generationmentioning

confidence: 99%

Section: The Model Of Vortex Generationmentioning

confidence: 99%

Section: B the Exponential Density Distribution Casementioning

confidence: 99%

Section: C Power-law Density Distribution Casementioning

confidence: 99%

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A mechanism of vortex generation in a supersonic flow behind a gas-plasma interface

Markhotok

2018

Fluid Dyn. Res.

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“…Since the shock and the flow instabilities take place upstream from the interface, the perturbations to the flow parameters propagating downstream, toward the interface, will disturb it. The overall pressure drop behind the perturbed (refracted) shock as a result of the flow parameter re-distribution [9] continuously mounting with time will be responsible for the sucking effect resulting in the large-scale interface perturbation moving it closer to the shock. The positive and essentially non-linear dynamics in the pressure perturbation evolution [9] will support amplification of this global perturbation to the interface.…”

Section: The Interface Stability Problem and Conclusionmentioning

confidence: 99%

A Shock Wave Instability Induced on a Periodically Disturbed Interface With Plasma

Markhotok

2018

IEEE Trans. Plasma Sci.

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The shock wave instability induced when interacting with a small waviness on an interface was investigated analytically and numerically. The perturbation to the shock was phenomenologically treated assuming this as the consequence of the shock refraction. The instability develops in the form of wave-like stretchings into the lower density medium followed with the loss of stability in the flow behind it, and eventually evolving into an intense vortex structure. The instability mode is aperiodical and unconditional, and either a transition to another stable state or continuous development as a secondary flow is possible. Among other interesting features are: a similarity law in the spatial and temporal evolution of the perturbations with respect to the interface curvature; the instability locus independence of the gas density distribution thus identifying the interface conditions as the sole triggering factor; the role of the density gradient in the instability evolution discriminating between qualitatively different outcomes; and the possibility of decay via non-viscous dumping mechanisms. The phenomenological connection between the shock and the interface stability is discussed.

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Drag reduction investigation for hypersonic lifting-body vehicles with aerospike and long penetration mode counterflowing jet

Fan

Xie

Qin

et al. 2018

Aerospace Science and Technology

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This study describes numerical computations of aerospike and counterflowing jet as drag reduction methods for a hypersonic lifting-body model for Mach 8 flow at 40 km altitude. The three-dimensional Navier-Stokes equation and the laminar condition have been utilized to obtain the flow field properties. Both steady-state and time-accurate computations are performed for the models in order to investigate the drag reduction effect and the periodic oscillation characteristics of long penetration mode (LPM) jet. Results showed that both of them can significantly modify the external flowfields and strongly weaken or disperse the shock-waves of the vehicle, then achieve an obvious drag reduction effect in the range of small angles of attack. The value is 7.25% for model with aerospike and 8.80% for model with counterflowing jet at angle of attack of 6 degree. Compared with aerospike, counterflowing jet shows a better drag reduction effect in the gliding angle of attack, and this leads to a larger lift-to-drag ratio of 3.58. Meanwhile, the displacement of center of pressure of the whole vehicle is smaller in the flight phase. The oscillation frequency of the counterflowing jet at angle of attack of 6 degree is 444Hz, and the oscillation characteristics of drag is due to the change of the pressure distribution caused by the oscillation of the shock structure. The results may be of high practical significance and show the possibility of developing a feasible system using counterflowing jet as an active flow control of reducing drag during hypersonic vehicle gliding with maximum lift-to-drag ratio.

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A mechanism of wave drag reduction in the thermal energy deposition experiments

Cited by 12 publications

References 34 publications

A mechanism of vortex generation in a supersonic flow behind a gas-plasma interface

A mechanism of vortex generation in a supersonic flow behind a gas-plasma interface

A Shock Wave Instability Induced on a Periodically Disturbed Interface With Plasma

Drag reduction investigation for hypersonic lifting-body vehicles with aerospike and long penetration mode counterflowing jet

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