Session *BB1.4

9:30 AM *BB1.4
PHYSICS OF ATOMIZATION, SPRAY DYNAMICS AND IMPACTION IN SPRAY PROCESSES. Norman Chigier, Spray Systems Technology Center, Carnegie Mellon University, Pittsburgh, PA.

Initial spray conditions are characterized by probability density functions of drop size, velocity, number density temperature and flux. These point pdfs change as a function of downstream and transverse location in the spray under the influence of atomization, coalescence, vaporization, dispersion, drag and interaction with high turbulence intensity gas streams. Differential velocities between drop and gas streams and inter-drop interactions result in drop accelerations, decelerations, deflections and recirculation. A complete control of the impaction process requires control of the spray characteristics during the process of impingement and gas flow deflection. The final deposit is directly dependent on the particle size, velocity, temperature, number density and flux in the spray immediately prior to impaction. Non-uniform thickness and densities of deposit can be traced to non-uniformities in spray characteristics. The Spray Systems Technology Center at Carnegie Mellon University studies the fundamental physical processes of atomization, spray dynamics and combustion of sprays with a wide range of industrial applications, including combustion in gas turbine, rocket and automobile engines, spray painting of automobiles, molten metal coatings and spray forming, agricultural spraying, inhalation therapy for respiratory illnesses, pharmaceutical spraying of tablet coatings, etc. Detailed measurements are made in sprays using image analysis, laser diffraction and phase Doppler interferometry. Measurements are made of single drop size, velocity and temperature in situ at ``points'' in the spray. Individual drop measurements are made in 1$\mu$sec, yielding very detailed and accurate size, velocity and temperature distributions and associated number density, flux and time of arrival measurements. These measurements provide insight to fundamental physical processes and lead to formulation of physical models for highly complex computer codes. The predicitions are subsequently validated by the measurements.