Characteristics of the mach disk in the underexpanded jet in which the back pressure continuously changes with time

Irie, Tsukasa; Yasunobu, Tsuyoshi; Kashimura, Hideo; Setoguchi, Toshiaki

doi:10.1007/s11630-003-0054-4

“…2f). This transition is consistent with the pressure ratio of five previously reported [17]. Since the focus of the present work is the propagation of the Mach disk shock in response to changing reservoir pressure during the blowdown, no further effort was made to identify the transition pressure ratio more exactly.…”

Section: Experimental Measurements Of Mach Disk Shock Locationsupporting

confidence: 90%

“…A time-dependent reservoir-to-ambient-pressure ratio has been previously shown to affect supersonic jet structure in the transition from regular to Mach reflection [17,18]. Gribben et al found hysteresis in the reflection transition of a Mach 3 jet, using quasi-steady simulations [18].…”

Section: Introductionmentioning

confidence: 99%

“…The Mach disk shock location as a function of decreasing or increasing pressure ratio was not reported. In a numerical study by Irie et al [17], the pressure ratio was varied by continuously increasing or decreasing the ambient pressure, while the reservoir pressure remained constant. A pressure ratio range of 3 to 15 and pressure rate of changes of 1:167, 0.835, and 0.5 were selected.…”

Section: Introductionmentioning

confidence: 99%

“…Their results show not only a hysteresis of the transition between Mach and regular reflection, but also a hysteresis in the location of the Mach disk shock location, decreasing below steadystate values for decreasing back pressure and increasing above for increasing back pressure. The critical pressure for Mach to regular reflection transition was found to depend on the flow history, and a hysteresis loop was calculated [17]. The damping effect of nonequilibrium condensation on hysteresis was examined by Kim et al [19].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Exhaust of Underexpanded Jets from Finite Reservoirs

Orescanin

¹

,

Prisco

²

,

Austin

³

2010

40th Fluid Dynamics Conference and Exhibit

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The response of an underexpanded jet to a depleting finite reservoir is examined with experiments and simulations. An open-ended shock-tube facility with a variable reservoir length is used to obtain images of nitrogen-and heliumjet structures at successive instances during the blowdown from initial pressure ratios of up to 250. The reservoir and ambient pressures are simultaneously measured to obtain the instantaneous pressure ratio. We estimate the time scales for jet formation and reservoir depletion as a function of the specific heat ratio of the gas and the initial pressure ratio. The jet structure formation time scale is found to become approximately independent of the pressure ratio for ratios greater than 50. In the present work, no evidence of time dependence in the Mach disk shock location is observed for rates of pressure decrease associated with isentropic blowdown of a finite reservoir while the pressure ratio is greater than 15. The shock location in the finite-reservoir jet can be calculated from an existing empirical fit to infinite-reservoir jet data evaluated at the instantaneous reservoir pressure. For pressure ratios below 15, however, the present data deviate from a compilation of data for infinite-reservoir jets. A new fit is obtained to data in the lower-pressure regime. The self-similarity of the jet structure is quantified, and departure from similarity is noted to begin at pressure ratios lower than about 15, approximately the same ratio that limits existing empirical fits.

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“…4b. The nondimensional time rate of change of the pressure discharge for the universal, isentropic blowdown curve is comparable in the initial stages to values examined by Irie et al [17]. …”

Section: Experimental Measurements Of Mach Disk Shock Locationsupporting

confidence: 79%

Exhaust of Underexpanded Jets from Finite Reservoirs

Orescanin

¹

,

Prisco

²

,

Austin

³

2010

Journal of Propulsion and Power

View full text Add to dashboard Cite

The response of an underexpanded jet to a depleting finite reservoir is examined with experiments and simulations. An open-ended shock-tube facility with a variable reservoir length is used to obtain images of nitrogen-and heliumjet structures at successive instances during the blowdown from initial pressure ratios of up to 250. The reservoir and ambient pressures are simultaneously measured to obtain the instantaneous pressure ratio. We estimate the time scales for jet formation and reservoir depletion as a function of the specific heat ratio of the gas and the initial pressure ratio. The jet structure formation time scale is found to become approximately independent of the pressure ratio for ratios greater than 50. In the present work, no evidence of time dependence in the Mach disk shock location is observed for rates of pressure decrease associated with isentropic blowdown of a finite reservoir while the pressure ratio is greater than 15. The shock location in the finite-reservoir jet can be calculated from an existing empirical fit to infinite-reservoir jet data evaluated at the instantaneous reservoir pressure. For pressure ratios below 15, however, the present data deviate from a compilation of data for infinite-reservoir jets. A new fit is obtained to data in the lower-pressure regime. The self-similarity of the jet structure is quantified, and departure from similarity is noted to begin at pressure ratios lower than about 15, approximately the same ratio that limits existing empirical fits.

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Flow structures of gaseous jets injected into water for underwater propulsion

Jianing

¹

,

Wang

²

,

Shyy

³

2011

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Gaseous jets injected into water are typically found in underwater propulsion, and the flow is essentially unsteady and turbulent. Additionally, the high water-to-gas density ratio can result in complicated flow structures; hence measuring the flow structures numerically and experimentally remains a challenge. To investigate the performance of the underwater propulsion, this paper uses detailed NavierStokes flow computations to elucidate the gas-water interactions under the framework of the volume of fluid (VOF) model. Furthermore, these computations take the fluid compressibility, viscosity, and energy transfer into consideration. This paper compares the numerical results and experimental data, showing that phenomena including expansion, bulge, necking/breaking, and back-attack are highlighted in the jet process. The resulting analysis indicates that the pressure difference on the rear and front surfaces of the propulsion system can generate an additional thrust. The strong and oscillatory thrust of the underwater propulsion system is caused by the intermittent pulses of the back pressure and the nozzle exit pressure. As a result, the total thrust in underwater propulsion is not only determined by the nozzle geometry but also by the flow structures and associated pressure distributions.

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Characteristics of the mach disk in the underexpanded jet in which the back pressure continuously changes with time

Cited by 30 publications

References 10 publications

Exhaust of Underexpanded Jets from Finite Reservoirs

Exhaust of Underexpanded Jets from Finite Reservoirs

Exhaust of Underexpanded Jets from Finite Reservoirs

Flow structures of gaseous jets injected into water for underwater propulsion

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