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Spray cooling is a topic of current interest for its ability to uniformly remove high levels of waste heat for densely packed microelectronics. A Monte-Carlo (MC) spray cooling simulation model is under development that is based on empirical data to be a cost effective design tool that will predict accurate heat fluxes based on nozzle conditions and heater geometry. This work reports spray and single drop experiments with the goal of computing the volume beneath a drop impact cavity (sub-cavity volume) created by a single impinging droplet on an initial liquid layer. A relevant test plan for the single drop experiments in terms of We and Re numbers was created through utilization of Phase Doppler Anemometry to characterize a water spray generated by a nozzle of interest for varying flow conditions. Liquid thickness profiles of the sub-cavity formed by a single impinging drop onto a range of initial liquid film thicknesses were measured versus time via a non-contact optical thickness sensor. Time dependent sub-cavity volumes were computed by integrating these sub-cavity liquid film thickness profiles measured radially outward from the impact centerline. It is found that higher We and lower h 0 * result in a more radially uniform sub-cavity surface contour versus time, except for regions near the outer bottom cavity radius, where the liquid film was thinner. The sub-cavity volume was found to be nearly constant for a majority of the cavity lifetime and increased with We and h 0 * . These results will be incorporated in future work into the MC model to improve its predictive capability. Nomenclatured = Drop diameter Greek Letters D = Arithmetic mean droplet diameter ρ = Density D 32 = Sauter mean droplet diameter η = Index of refraction Fr = Froude number = μ = Dynamic viscosity h = Liquid film thickness σ = Surface tension R = Radial location τ = Dimensionless time (t•V axial /d) Re = Reynolds number = Superscripts T = Temperature * = Dimensionless parameter t = Time Subscripts V = Arithmetic mean velocity 0 = Initial condition Vol = Sub-cavity volume axial = Axial velocity component We = Weber number = c = Cavity z = Axial standoff distance from the nozzle tip r = Radial velocity component s = Spray

The motion of air and solid particles is examined in a fluidically oscillating slot jet using time-averaged and cycle-resolved laser Doppler anemometry measurements. These measurements reveal the time dependent relative velocity magnitudes between the phases as well as the detailed nature of the flulidcally oscillating slot jet. Temporal phase differences between the gas and solid phases ranged up to 40 degrees for jet oscillation frequencies up to 50 Hz. The results indicate that the fluidic nozzle is an effective particle spreading device and the fuel injector attributes are inherently present such as enhanced mixing and low velocity regions for flame anchoring.

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