Julie Ann Johnson

Evidence of turbulence in laser-induced plasmas

By focusing a pulsed single mode Nd:YAG laser, we created low temperature plasmas at various pressures with various target gases and collected spectral light emissions to investigate the possibility of turbulent behavior in these types of plasmas. Characteristic fluctuation frequencies, chaotic dimensions, spectral indices, and turbulent fluctuation energies are determined from fluctuations in these spectral light emissions. Values calculated for the spectral index and the chaotic index for each plasma event are found to be within the known values for other turbulent plasma systems. Thus, turbulent fluctuations on a nanosecond time scale are confirmed in the time evolutions of various singly ionized and neutral spectral lines of various gases.

Turbulent transport manipulation in the internal combustion engine as a second order phase transformation

Using hot-wire anemometry in a motored engine, new turbulence physics is observed in the evolution and sensitivity of characterizing parameters to changing molecular weights. Turbulent manipulation of mixing is afforded along with a role for nonequilibrium statistical mechanics in turbulence phenomenology.

Atomic effects in the turbulent properties of microwave generated plasmas

Summary form only given, as follows. Microwave plasmas are generated in helium, neon, argon, krypton, and xenon at various microwave powers and neutral gas pressures. A floating Langmuir double probe is employed to diagnose plasma electron density and temperature. Bias voltage and current characteristic curves are analyzed for the determination of electron temperature and density for all five gases. Turbulence analysis is carried out by using time resolved neutral line emission data from these gases at a sampling rate of 100 MHz. Fourier spectra of emission fluctuations allow determinations of the total turbulent energy and the characteristic turbulent fluctuation frequency, which is also evidenced by the periodic motion in the phase space trajectory. The computations for chaotic dimension are also carried out for all five species. Systematic trends in the turbulent parameters show a dependence on atomic weight. These trends are consistent with observations of molecular influence on turbulent transport found in other plasmas and neutral gases and with current theoretical models.