Raman Studies of Free Jet Expansion (Diagnostics and Mapping)

Montero, S.; Maté, Belén; Tejeda, Guzmán; Fernández, J. M.; Ramos, Ángel

doi:10.1007/978-3-642-56800-8_20

Cited by 11 publications

(17 citation statements)

References 8 publications

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“…For the present jet a variable specific heat ratio ranging from γ = 1.31 at the nozzle exit, to γ = 1.36 at z ≈ 50R e has been deduced from the experimental vibrational cooling (Montero et al 2000). In the QGD calculations a fixed value γ = 1.35 has been assumed along the jet, corresponding to ξ = 2.7 excited internal degrees of freedom (2 rotational + 0.7 vibrational) according to the relation (Bird 1994)…”

Section: Numerical Calculationsmentioning

confidence: 99%

Experimental and numerical investigation of an axisymmetric supersonic jet

et al. 2001

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A comprehensive study of a steady axisymmetric supersonic jet of CO 2 , including experiment, theory, and numerical calculation, is presented. The experimental part, based on high-sensitivity Raman spectroscopy mapping, provides absolute density and rotational temperature maps covering the significant regions of the jet: the zone of silence, barrel shock, Mach disk, and subsonic region beyond the Mach disk. The interpretation is based on the quasi-gasdynamic (QGD) system of equations, and its generalization (QGDR) considering the translational-rotational breakdown of thermal equilibrium. QGD and QGDR systems of equations are solved numerically in terms of a finite-difference algorithm with the steady state attained as the limit of a time-evolving process. Numerical results show a good global agreement with experiment, and provide information on those quantities not measured in the experiment, like velocity field, Mach numbers, and pressures. According to the calculation the subsonic part of the jet, downstream of the Mach disk, encloses a low-velocity recirculation vortex ring.

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Section: Numerical Calculationsmentioning

confidence: 99%

Experimental and numerical investigation of an axisymmetric supersonic jet

et al. 2001

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“…These ratios were chosen to produce normal shock waves differing considerably in their properties, spanning a range of Mach numbers 7.7 < M < 15.3, reaching maximum values of local Knudsen numbers 0.33 < Kn < 0.59 within the shock wave. The absolute density profiles and the rotational temperature profiles of these five shock waves have been measured with unprecedented accuracy and spatial resolution by means of high-sensitivity Raman spectroscopy using the miniature jet diagnostic facility at the Instituto de Estructura de la Materia (Montero et al 2000.…”

Section: Introductionmentioning

confidence: 99%

A study of shock waves in expanding flows on the basis of spectroscopic experiments and quasi-gasdynamic equations

Graur¹,

Елизарова²,

Ramos

et al. 2004

J. Fluid Mech.

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A comprehensive numerical and experimental study of normal shock waves in hypersonic axisymmetric jets of N 2 is presented. The numerical interpretation is based on the quasi-gasdynamic (QGD) approach, and its generalization (QGDR) for the breakdown of rotational-translational equilibrium. The experimental part, based on diagnostics by high-sensitivity Raman spectroscopy, provides absolute density and rotational temperatures along the expansion axis, including the wake beyond the shock. These quantities are used as a reference for the numerical work. The limits of applicability of the QGD approach in terms of the local Knudsen number, the influence of the computational grid on the numerical solution, the breakdown of rotation-translation equilibrium, and the possible formation of a recirculation vortex immediately downstream from the normal shock wave are the main topics considered.

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“…͑10͔͒ along the jets. These values have been measured at fixed points corresponding to kinetic temperatures T t = 35, 28,22,18,14,10,8,6, and 4 K. At these points, which approximately span along the jet the domain of 1250ഛ z ഛ 14800 m, 40ജ T r ജ 7 K, and 15ϫ 10 22 ജ n ജ 4 ϫ 10 20 m −3 , the ratio,…”

Section: Discussionmentioning

confidence: 99%

“…[26][27][28] The link between experiment ͑the axial region of the jet expansion͒ and theory ͑the calculated collisional rates of previous section͒ is provided by the master equation ͑MEQ͒,…”

Section: Experimental Methodologymentioning

confidence: 99%

Inelastic collisions in molecular nitrogen at low temperature (2⩽T⩽50K)

Fonfría¹,

Ramos²,

Thibault³

et al. 2007

The Journal of Chemical Physics

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Theory and experiment are combined in a novel approach aimed at establishing a set of two-body state-to-state rates for elementary processes ij → ᐉm in low temperature N 2 :N 2 collisions involving the rotational states i , j , ᐉ , m. First, a set of 148 collision cross sections is calculated as a function of the collision energy at the converged close-coupled level via the MOLSCAT code, using a recent potential energy surface for N 2 -N 2 . Then, the corresponding rates for the range of 2 ഛ T ഛ 50 K are derived from the cross sections. The link between theory and experiment, aimed at assessing the calculated rates, is a master equation which accounts for the time evolution of rotational populations in a reference volume of gas in terms of the collision rates. In the experiment, the evolution of rotational populations is measured by Raman spectroscopy in a tiny reference volume ͑Ϸ2 ϫ 10 −3 mm 3 ͒ of N 2 traveling along the axis of a supersonic jet. The calculated collisional rates are assessed experimentally in the range of 4 ഛ T ഛ 35 K by means of the master equation, and then are scaled by averaging over a large set of experimental data. The scaled rates account accurately for the evolution of the rotational populations measured in a wide range of conditions. Accuracy of 10% is estimated for the main scaled rates.

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Raman Studies of Free Jet Expansion (Diagnostics and Mapping)

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Cited by 11 publications

References 8 publications

Experimental and numerical investigation of an axisymmetric supersonic jet

Experimental and numerical investigation of an axisymmetric supersonic jet

A study of shock waves in expanding flows on the basis of spectroscopic experiments and quasi-gasdynamic equations

Inelastic collisions in molecular nitrogen at low temperature (2⩽T⩽50K)

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