Flow features of shock-induced combustion around projectile travelling at hypervelocities

Matsuo, Akiko; Fujiwara, Toshi; Fujii, Kozo

doi:10.2514/6.1993-451

Cited by 10 publications

(7 citation statements)

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“…Lehr 1 and McVey and Toong 2 reported that unsteady combustion was observed around a spherical projectile flying at hypersonic velocity in detonable gases. Two typical oscillation modes were reported in previous studies: [1][2][3][4][5][6][7] One is referred to as the "regular regime," whose oscillations have high frequency ͑HF͒ and low amplitude, and the other is referred to as the "large-disturbance regime," whose oscillations have low frequency ͑LF͒ and high amplitude. The details of these oscillation modes have been revealed by numerical studies.…”

Section: Introductionmentioning

confidence: 97%

Unsteady features on one-dimensional hydrogen-air detonations

Daimon

Matsuo

2007

Physics of Fluids

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The features of one-dimensional unsteady detonations are studied numerically using a hydrogen-air detailed chemical reaction model. A series of simulations are carried out while degree of overdrive, initial pressure, initial temperature, and equivalence ratio are varied. The oscillation modes and mechanisms of the one-dimensional detonations are discussed with reference to shock pressure histories and x-t diagrams of density distributions. As the degree of overdrive is reduced with a stoichiometric mixture of hydrogen-air at P 0 = 0.421 atm and T 0 = 293 K, a steady state appears, along with a high-frequency mode and a low-frequency mode. The oscillation mechanism of the high-frequency mode is the same as that of the regular regime of unsteady shock-induced combustion observed around a spherical projectile flying at hypersonic velocity in detonable gases. The degree of overdrive threshold between the steady and unsteady region increases monotonically with initial pressure and decreases monotonically with initial temperature. When the equivalence ratio is changed, the threshold has a minimum value around = 1. We focus attention on a nondimensional effective activation energy, which is generally used for linear stability analysis. The oscillation mode depends highly on the nondimensional effective activation energy. The oscillation of the detonation front appears as the nondimensional effective activation energy goes past a threshold value of 5.2. Furthermore, we investigate the failed regime and possible reignition in this regime. In the failed regime, a detonation wave breaks up into a leading shock, a contact discontinuity, and a rarefaction wave. When the shock is weak, reignition time becomes very long. Therefore, the reignition after the failed regime is difficult to reproduce in the restricted computational domain. The reignition process in the failed regime is investigated by means of analysis consisting of integration along the point of intersection between a Rayleigh line for weak leading shock and a partially burnt Hugoniot curve. The reignition time increases dramatically with decreasing temperature behind the shock wave, when the gas condition goes past the second explosion limit. The second explosion limit is one of the characteristics of the hydrogen-air detailed chemical reaction model and does not exist in the one-step chemical reaction model. Lastly, the reignition time obtained by the analysis is compared with that obtained by the simulation results. The simulation results agree well with the analytical results.

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Section: Introductionmentioning

confidence: 97%

Unsteady features on one-dimensional hydrogen-air detonations

Daimon

Matsuo

2007

Physics of Fluids

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“…We are not sure whether M = 6.7 case is steady or not. The two cases were thought to be steady‐state flows based on coarse to medium mesh simulation in quite a few papers .…”

Section: Numerical Resultsmentioning

confidence: 99%

“…We are not sure whether M D 6.7 case is steady or not. The two cases were thought to be steady-state flows based on coarse to medium mesh simulation in quite a few papers [6,7,9]. We have conducted both viscous and inviscid simulations and used different CFL numbers as demonstrated in Figure 4(d), but results on the 768 2 fine mesh are still not converged.…”

Section: Discussionmentioning

confidence: 99%

Convergence issues in using high‐resolution schemes and lower–upper symmetric Gauss–Seidel method for steady shock‐induced combustion problems

2012

Numerical Methods in Fluids

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SUMMARYThis paper reports numerical convergence study for simulations of steady shock‐induced combustion problems with high‐resolution shock‐capturing schemes. Five typical schemes are used: the Roe flux‐based monotone upstream‐centered scheme for conservation laws (MUSCL) and weighted essentially non‐oscillatory (WENO) schemes, the Lax–Friedrichs splitting‐based non‐oscillatory no‐free parameter dissipative (NND) and WENO schemes, and the Harten–Yee upwind total variation diminishing (TVD) scheme. These schemes are implemented with the finite volume discretization on structured quadrilateral meshes in dimension‐by‐dimension way and the lower–upper symmetric Gauss–Seidel (LU–SGS) relaxation method for solving the axisymmetric multispecies reactive Navier–Stokes equations. Comparison of iterative convergence between different schemes has been made using supersonic combustion flows around a spherical projectile with Mach numbers M = 3.55 and 6.46 and a ram accelerator with M = 6.7. These test cases were regarded as steady combustion problems in literature. Calculations on gradually refined meshes show that the second‐order NND, MUSCL, and TVD schemes can converge well to steady states from coarse through fine meshes for M = 3.55 case in which shock and combustion fronts are separate, whereas the (nominally) fifth‐order WENO schemes can only converge to some residual level. More interestingly, the numerical results show that all the schemes do not converge to steady‐state solutions for M = 6.46 in the spherical projectile and M = 6.7 in the ram accelerator cases on fine meshes although they all converge on coarser meshes or on fine meshes without chemical reactions. The result is based on the particular preconditioner of LU–SGS scheme. Possible reasons for the nonconvergence in reactive flow simulation are discussed.Copyright © 2012 John Wiley & Sons, Ltd.

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“…The key parameters for the triggering of instabilities has been identified by vari ous parametric studies [20]- [22]. Matsuo and Fujiwara [20] and Ahuja and Tiwari [21] showed that an underdriven case, which shows instabilities in the reaction front, can be made stable by having an appropriately small size projectile and an overdriven case can be made unstable by having a large size projectile. Kumar and Singh [22] concluded that the key parameters for triggering these instabilities were projectile velocity, activation temperature, projectile nose radius, reaction rate constant, and heat release.…”

Section: Literature Surveymentioning

confidence: 99%