Planar 2D velocity measurements in the cap shock pattern of a thrust optimized rocket nozzle

Ramsey, Marc; Pitz, Robert W.; Jenkins, Thomas E.; Matsutomi, Yu; Yoon, Changjin; Anderson, William E.

doi:10.1007/s00193-011-0340-0

Cited by 10 publications

(3 citation statements)

References 29 publications

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“…Several numerical results 4,11 have indicated that such a convex shock will result in a trapped vortex downstream, although recent experimental studies using hydroxyl tagging velocimetry produced no experimental evidence of recirculating flow. 12 Significant questions remain about the Mach disk: the behaviour of coherent structures in the annular shear layer and the presence of a trapped vortex being two exemplars. This paper thus aims to study in detail the region around the Mach disk, and address some of these outstanding issues.…”

Section: Introductionmentioning

confidence: 99%

The underexpanded jet Mach disk and its associated shear layer

2014

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High resolution planar particle image velocimetry is used to measure turbulent quantities in the region downstream of the Mach disk in an axisymmetric underexpanded jet issuing from a convergent nozzle. The internal annular shear layer generated by the slip line emanating from the triple point is shown to persist across multiple shock cells downstream. A triple decomposition based on Proper Orthogonal Decomposition shows that the external helical structure associated with the screech tone generated by the jet exerts a strong influence on velocity fluctuations in the initial region of the annular shear layer. This influence manifests as the external vortices producing oscillatory motion of the Mach disk, and thus a forcing of the internal annular shear layer. The internal shear layer is characterized by a number of azimuthal modes of varying wavenumber and type, including both helical and axisymmetric modes. Finally, the possibility of a previously hypothesized recirculation region behind the Mach disk is investigated, with no evidence found to support its existence.

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Section: Introductionmentioning

confidence: 99%

The underexpanded jet Mach disk and its associated shear layer

2014

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“…Single-photon photodissociation of H 2 O with a 193 nm ArF laser was used to measure the line-of-sight averaged velocity in a shock tube by recording the displaced line position with UV absorption [17]. Hydroxyl tagging velocimetry (HTV) has been developed where a 193-nm ArF laser photodissociates H 2 O in a single-photon process to produce a large grid (up to 11 × 11 lines) of OH that is imaged by a second laser to determine the velocity in low-and high-temperature reacting flows in a two-dimensional plane [15,[18][19][20][21][22]. The HTV method has been used to measure supersonic flows in wind tunnels [20,21] and rocket exhausts [22].…”

Section: Introductionmentioning

confidence: 99%

“…Hydroxyl tagging velocimetry (HTV) has been developed where a 193-nm ArF laser photodissociates H 2 O in a single-photon process to produce a large grid (up to 11 × 11 lines) of OH that is imaged by a second laser to determine the velocity in low-and high-temperature reacting flows in a two-dimensional plane [15,[18][19][20][21][22]. The HTV method has been used to measure supersonic flows in wind tunnels [20,21] and rocket exhausts [22]. Although the OH tag can be long-lived at high temperature [15,18], at room temperature the OH lifetime is about 20 µs [19], limiting lowtemperature application to moderate-and high-speed flows.…”

Section: Introductionmentioning

confidence: 99%

N2O molecular tagging velocimetry

Elbaz

Pitz

2012

Appl. Phys. B

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A new seeded velocity measurement technique, N 2 O molecular tagging velocimetry (MTV), is developed to measure velocity in wind tunnels by photochemically creating an NO tag line. Nitrous oxide "laughing gas" is seeded into the air flow. A 193 nm ArF excimer laser dissociates the N 2 O to O( 1 D) that subsequently reacts with N 2 O to form NO. O 2 fluorescence induced by the ArF laser "writes" the original position of the NO line. After a time delay, the shifted NO line is "read" by a 226-nm laser sheet and the velocity is determined by time-of-flight. At standard atmospheric conditions with 4% N 2 O in air, ∼1000 ppm of NO is photochemically created in an air jet based on experiment and simulation. Chemical kinetic simulations predict 800-1200 ppm of NO for 190-750 K at 1 atm and 850-1000 ppm of NO for 0.25-1 atm at 190 K. Decreasing the gas pressure (or increasing the temperature) increases the NO ppm level. The presence of humid air has no significant effect on NO formation. The very short NO formation time (<10 ns) makes the N 2 O MTV method amenable to low-and highspeed air flow measurements. The N 2 O MTV technique is demonstrated in air jet to measure its velocity profile. The N 2 O MTV method should work in other gas flows as well (e.g., helium) since the NO tag line is created by chemical reaction of N 2 O with O( 1 D) from N 2 O photodissociation and thus does not depend on the bulk gas composition.

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Temperature measurement based on fluorescence intensity in hydroxyl tagging velocimetry (HTV)

Zhang

et al. 2020

AIP Advances

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Hydroxyl tagging velocimetry (HTV) is generally used for velocity measurement especially in the high-temperature and high-velocity flow field. In this work, according to the monotonous change of OH fluorescence intensity with temperature, the relative temperature distribution could be observed from the intensity distribution along the hydroxyl fluorescence line. We could obtain the temperature along the photodissociation line by calibrating at two positions. In this way, HTV has the potential for simultaneously achieving velocity and temperature without adding extra diagnostic systems.

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Planar 2D velocity measurements in the cap shock pattern of a thrust optimized rocket nozzle

Cited by 10 publications

References 29 publications

The underexpanded jet Mach disk and its associated shear layer

The underexpanded jet Mach disk and its associated shear layer

N2O molecular tagging velocimetry

Temperature measurement based on fluorescence intensity in hydroxyl tagging velocimetry (HTV)

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