Relaxation Processes in Shock Waves

The evolution of oxygen molecule vibrational temperature behind the front of a shock wave was studied at shock wave velocities 3 4.5 km/s and gas pressure ahead of the shock front 1 5 Torr. The results of vibrational temperature measurement con¦rmed the conception of separation of vibrational relaxation and dissociation zones behind the shock wave front at T ≤ 6500 K. It is observed that at T = 6500 10 500 K the vibrational temperature decreased in comparison with its value characterized by the achievement of vibrational translational equilibrium before the dissociation started. It is shown that the model should to be modi¦ed to describe the evolution of the oxygen vibrational temperature under the conditions of vibrational relaxation and dissociation coupling.

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“…For oxygen, the separation of the zones corresponds to the gas temperature not higher than 5000 K [7,8].…”

Section: Determination Of the Vibrational Oxygen Temperaturementioning

confidence: 99%

Experimental study and numerical modeling of vibrational oxygen temperature profiles behind a strong shock wave front

Забелинский

Ibraguimova

Shatalov

et al. 2012

Progress in Flight Physics

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“…A similar pattern is observed for all the studied wavelengths. Comparison with other experimental data shows that condition (5) is not met in [1] and that the agreement with the results in [3] is satisfactory.…”

Section: (5)mentioning

confidence: 56%

“…The gas parameters at this point (temperature, pressure, density, and concentration of the components) were calculated assuming that the vibrations of the molecules are completely excited, and the chemical reactions have not yet begun. Such a temporal separation of the vibrational relaxation and dissociation zones for the oxygen molecules is valid up to temperatures of +5000 K [5]. In this case, in order to calculate the flow parameters of the gas mixture behind the shock wave front, it is sufficient to solve the system of equations representing the familiar relationships for conservation of mass, momentum, and energy fluxes at the shock discontinuity, together with the equation of state:…”

mentioning

confidence: 99%

Determination of absorption cross sections for oxygen molecules in the Schumann-Runge band region at high temperatures

2006

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We have measured the absorption cross sections of oxygen molecules in oxygen and in an oxygen-argon mixture heated by a shock wave, in the wavelength range 190-250 nm at temperatures of 1500-7000 K, for thermal equilibrium conditions behind the shock wave front. Analysis of the absorption cross sections obtained allowed us to select a data set that adequately describes the absorption characteristics of the electronic tran-In order to approximate the temperature dependence of these cross sections at a temperature of 1500-4500 K, we chose the function σ(λ, T) = σ 0 (λ)(1 -exp (-θ/T)) exp (-n * θ/T) where σ 0 = 1.4⋅10 -17 , 1.4⋅10 -17 , 1.2⋅10 -17 , and 1.3⋅10 -17 cm 2 , n * = 3. 1, 4.1, 5.6, and 7.47 for wavelengths 190, 210, 230, and 250 nm, respectively; θ = 2240 K is the characteristic temperature of the O 2 molecules. The approximation error was 19-25% and did not exceed the experimental error.Key words: absorption cross section of molecular oxygen, Schumann-Runge system, electronic transition, UV spectrum, electronic ground state and excited state of a molecule, shock wave.Introduction. Experimental studies of oxygen absorption cross sections were carried out earlier in [1-3] at high temperatures behind the front of both an incident and a reflected shock wave. The aim of this work was to determine the absorption cross sections of oxygen molecules at high temperatures under thermal equilibrium conditions behind a shock wave front. Such measurements can be properly made only when the optical thickness of the absorbing gas layer is small, but it is not always possible to control this parameter without preliminary information about the absorption cross sections. Our analysis of the measured cross sections and comparison of the data obtained with the results in [1-3] have allowed us to solve this problem.The experiment. The experiments were carried out in a shock tube with inner diameter 50 mm. The highpressure chamber was filled with hydrogen to a pressure of 10 atm, or else with a stoichiometric mixture of hydrogen and oxygen (30%), diluted with an inert gas (70%), to a pressure of 4.5 atm. In the second case, the mixture was ignited by a discharge, as a result of which the gas pressure increased by a factor of 6-8 while the temperature of the gas in the high-pressure chamber increased up to 1500 K. The gas under study was admitted to the low-pressure chamber at a pressure from 2 to 30 torr: either undiluted oxygen, or a mixture of oxygen and argon with oxygen content from 10 to 50%.After rupture of the membrane separating the high-pressure and low-pressure channels of the shock tube, the shock wave propagates at a velocity of 1.2-3.5 km/sec through the gas filling the low-pressure channel. The velocity of the shock wave was measured using Suntsov piezoelectric transducers [4] mounted on the walls of the shock tube. The uncertainty in the velocity measurement was no greater than 1%. The temperature, gas pressure, and concentration of oxygen molecules were determined in standard calculations for gas flow behind a...

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“…It is necessary to pay attention to the deviation of the dependence of the velocity constant from the Landau-Teller linear dependence in the low-and high-temperature ranges. At low temperatures, the deceleration of the decrease of the velocity constant is defined by the increasing role ~act -----0.391 eV of intermolecular attractive forces [23]. The action of the attractive forces results in the fact that molecules start to approach each other with increasing relative velocity, which leads to an increase in the transition probability per single collision and, hence, to an increase in the velocity constant.…”

Section: Analytic Continuation Of the Velocity Constantsmentioning

confidence: 99%

Application of the inverse-problem method for the calculation of the probability characteristics of elementary processes

et al. 1999

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Relaxation Processes in Shock Waves

Cited by 28 publications

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Experimental study and numerical modeling of vibrational oxygen temperature profiles behind a strong shock wave front

Experimental study and numerical modeling of vibrational oxygen temperature profiles behind a strong shock wave front

Determination of absorption cross sections for oxygen molecules in the Schumann-Runge band region at high temperatures

Application of the inverse-problem method for the calculation of the probability characteristics of elementary processes

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