Vibrational data, temperature-velocity

Temperature-Velocity Correlation Measurements for Turbulent Diffusion Flames from Vibrational Raman-Scattering Data... 

Determination of the total excitation cross section is again done by observing the resonance-line emission. Both the initial relative kinetic energy and the N2 temperature may be varied. First experiments of this type have studied the excitation of Na(3p) by N2, H2, and D2, vibrationally excited at 2000 to 3000°K for initial relative velocities from 1000 to 4000 m/sec l25-126 as well as both potassium and sodium.127 Recent studies with seeded beams 128131 on K + N2 and K + CO involved lower initial vibrational states v. This type of experiment is very difficult to analyze and evaluation invokes a number of assumptions for fitting the experimental data. A special threshold law for the energy dependence of the partial cross sections is adopted ... 

These are the quantities to which we are giving our attention. Vibrational Raman scattering is being used for the temperature and density data, and, when taken simultaneously with velocity data from coupled LV instrumentation (.8), provides also the fluctuation mass flux through use of fast chemistry assumptions and the ideal gas law for atmospheric pressure flames. 

Here is yet another example. A projectile hits a wall ( armor ). Fig. 7.12. The projectile is composed of Lemiard-Jones atoms (with some Sp and p. 347), and we assume the same for the wall (for other values of the parameters, let us make the wall less resistant than the projectile Sw < Sp and Ve,w > fe,p ) All together, we may have hundreds of thousands (or even miUions) of atoms (i.e., there are millions of differential equations to solve). Now, we prepare the input Rq and vq data. The wall atoms are assumed to have stochastic velocities drawn from the MaxweU-Boltzmaim distribution for room temperature. The same for the projectile atoms, but additionally, they have a constant velocity component along the direction pointing to the wall. At first, nothing particularly interesting happens-the projectile flies toward the wall with a constant velocity (while aU the atoms of the system vibrate). Of course, it is most interesting when the projectile hits the wall. Once the front part of the projectile touches the wall, the wall atoms burst into space in a kind of eruption, the projectile s tip loses some atoms, and the spot on the wall hit by the projectile vibrates and sends a shock wave. 

Particle velocities are then gradually increased until they correspond to the temperature of interest for the system, and the dynamics are continued for -lO At intervals or until the distribution of velocities is Maxwellian. On achieving this condition, the dynamics describe a thermal equilibrium, and V/,Xy,/ data are collected over an additional period of 10 -10 time steps At. This maximum number of steps that is practicable thereby limits the total time interval of the dynamics to about 10 s. Accordingly no relaxations can be simulated with characteristic times longer than this. A limitation must sometimes be imposed at the shorter end of the time scale to investigate dynamics with long characteristic times, it may be necessary to use a time step At that is longer than the period of a bond vibration ( IQ-i s) jjj cases force constants are used that are diminished, typically by afactor of 7. 

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