Charlemagne C. Akpovo

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.

LIBS on Silicon Oxide and Nitride Thin Films

Single and double pulse LIBS were employed to study the amount of material removal and percent ionization as a function of trace and bulk material, in ambient atmosphere.

Molecular effects on turbulent diffusion and energy in a low speed closed flow

The coefficient of turbulent diffusion and the total turbulent energy are determined during the compression phase of a motored internal combustion engine with varying flow conditions and using intake gases with varying molecular weights. These turbulent parameters change with time and with intake gas molecular weight. However, under all flow conditions, both parameters first increase and then decrease with increasing molecular weight. In addition, a direct correlation is observed between the average values of the coefficient of turbulent diffusion and the average values of the total turbulent energy, irrespective of the molecular weight.

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.