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Governing Equations of Fluid Mechanics and Heat Transfer
Published in Dale A. Anderson, John C. Tannehill, Richard H. Pletcher, Munipalli Ramakanth, Vijaya Shankar, Computational Fluid Mechanics and Heat Transfer, 2020
Dale A. Anderson, John C. Tannehill, Richard H. Pletcher, Munipalli Ramakanth, Vijaya Shankar
The energy of a gas molecule is expressed as a sum of four principal components: Translational, Vibrational, Rotational and Electronic energies: e=et+ev+er+ee. Depicted in Figure 5.4, these refer to the energy associated with translation through space, vibration of the atoms, rotation about a certain axis, and the energy contained by electrons (kinetic and potential). Vibration and rotational modes are only present in polyatomic molecules. Each of these modes of energy is associated with a temperature when the number density of particles in each mode has a Maxwell-Boltzmann distribution. These temperatures are referred to by the names of their corresponding energy modes: Translational temperature Tt, Vibrational temperature Tv, Rotational temperature Tr, and electron/electronic temperature Te. As noted earlier for thermally perfect gases, the energy may be written as a function of temperature for each of these modes.
Chemical lasers
Published in E R Pike, High-power Gas Lasers, 1975, 2020
In looking at the data in figure 7 we also see two other important effects. One effect is that there is a steady increase in the rotational quantum number J of the transitions which are lasing as time progresses during the pulse. This occurs because of a rise in the rotational temperature and a decrease in the vibrational temperature (or, the inversion ratio), both of which cause higher J lines to have higher gain. The second effect is that at any given time, several different rotational lines can be simultaneously lasing within each vibrational band. This is somewhat surprising, since in lasers such as CO2 only one J-transition is normally seen to lase at any time. In the case of the chemical laser, this effect implies that rotational thermalization is sufficiently slow that laser action can cause the rotational distributions to be non-Boltzmann in nature. (This effect could also be caused experimentally by a spatially non-uniform gain medium.)
Section 7.2: Spatially Resolved Spectroscopic Analysis of the Plasma
Published in Mark A. Prelas, Galina Popovici, Louis K. Bigelow, Handbook of Industrial Diamonds and Diamond Films, 2018
A. Gicquel, M. Chenevier, M. Lefebvre
Typical axial distributions are given in figure 8 for the following experimental conditions: power 600 W, pressure 25 hPa, power density of 9 W cm−3, flow rate =300 seem, substrate temperature = 900°C. The rotational temperature reaches 2150 K ± 50 K and the vibrational temperature 2250 K + 100 K in the bulk of the plasma. A quasiequilibrium between these two temperatures is observed: the vibrational temperature is higher than the rotational by not more than 100 K.
Vibrationally- and rotationally-resolved photoelectron imaging of cryogenically-cooled SbO2 –
Published in Molecular Physics, 2023
G. Stephen Kocheril, Han-Wen Gao, Lai-Sheng Wang
The FC simulation yielded an anion vibrational temperature of 80 ± 10 K. This temperature is consistent with the vibrational temperature of BiO2– that we obtained recently [17]. However, it is higher than what we expected relative to the rotational temperature we were able to obtain for organic molecular anions from our third-generation ESI-PES apparatus [30–32]. This observation demonstrates the importance of tuning the RF voltage on the Paul trap and its impact on the final anion temperature. As well known in ion-trap mass spectrometry [28], ion temperatures in the Paul trap depend on the q-value, which is directly related to the RF voltage. A large q-value (large RF voltage) results in less effective cooling or even RF heating. By varying the RF voltage or the q-value, we are able to tune the temperature of the trapped ions, while balancing the trapping efficiency. The spectra shown in Figure 2b and c using RF = 300 V exhibit a relatively high vibrational temperature of 80 K, while the spectrum in Figure 2a using RF = 250 V indicates significantly colder anions since the hot band population is negligible. However, a larger RF amplitude was necessary at the higher photon energies in order to increase the trapping efficiency to allow data acquisition in a reasonable time frame due to the low detachment photon flux from the frequency-doubled dye laser output.
HALO3D: An All-Mach Approach to Hypersonic Flows Simulation
Published in International Journal of Computational Fluid Dynamics, 2022
Vincent Casseau, Wenbo Zhang, Shrutakeerti Mallikarjun, Wagdi G. Habashi, Song Gao, Abolfazl Karchani
An application of the HALO3D flow module is presented in Figure 5 for the laminar thermo-chemical non-equilibrium airflow past the Mars entry spacecraft experimental model tested in the HYPULSE hypersonic experimental facility and whose geometry can be found in (Hollis 1996). Blottner and Eucken's transport model is used in conjunction with a Lewis number of 1.4 for diffusion modelling and the electronic energy mode is neglected. The reaction data from the DPLR code (Scalabrin and Boyd 2005) is used for the forward reaction rates, while equilibrium constants are evaluated from Gibbs free energy. An isothermal non-catalytic wall is used with a wall temperature of 300 K. The optimised grid in Figure 5a produces a very sharp bow shock shown in Figure 5b. Temperature and mass fraction profiles along the stagnation line are presented in Figure 5c and d, with comparisons to numerical results (Scalabrin and Boyd 2005). The agreement in terms of shock standoff distance and peak trans-rotational temperature is reasonable and the optimised unstructured mesh produces a sharper shock than that of the structured one. The vibrational temperature has a less pronounced post-shock peak and is overall slightly higher than the trans-rotational temperature in the shock layer. Mass fraction profiles for both structured and unstructured meshes agree well with the reference away from the wall, but the optimised mesh results are the only ones showing a good concordance close to the surface, as shown in the magnified view in Figure 5d.
Optical emission generated by particle impact during aerosol deposition of alumina films
Published in Journal of Asian Ceramic Societies, 2022
Yasuhito Matsubayashi, Tsuyohito Ito, Kentaro Shinoda, Kazuo Terashima, Jun Akedo
Figure 6 shows the dependence of rotational temperature and vibrational temperature of N2 calculated from 2PS on the flow rate for N2 carrier gas. The gas temperature can be estimated from the rotational temperature, which approximately equilibrates with the gas temperature [36,43]. The measured rotational temperatures were around 300 K, irrespective of flow rate, indicating that the discharges did not generate much heat. The vibrational temperature was much higher, at around 3000 K. Thus, the optical emission measurements suggested that in the discharges, the temperature of the electrons, which excite gas molecules, was much higher than that of the surrounding gas. Although further research is required to understand the slight decrease in vibrational temperature with the increase in flow rate, it could be caused by the shorter duration of gas with a higher flow rate or by the electron temperature change in the plasma [44]. The increase in flow rate increases the pressure inside the chamber and aerosol density, which strongly affects discharge properties. In particular, introducing microparticles into a plasma decreases the electron density and increases the electron temperature [45].