RAIN SIMULATION IN TRANSONICS FLOWS

Erosion of aerodynamic components by rain has traditionally been studied with a rotating arm, where the component is swung into a water spray simulating rainfall. This method, for obvious reasons, is not well suited for testing componets that are large and heavy. Arnold Engineering Development Center (AEDC) has a need for a steady state test facility capable of simulating rain (up to transonic speeds) impacting aircraft components and materials. A system is proposed herein which will typically produce, 1.5mm rain droplets and a liquid water content of approximately 20gm/m3 which is prototypical of a very heavy shower. The proposed system utilizes a novel spray nozzle which discharges a laminar water jet at supercritical Reynolds Numbers. The Phase I effort will demonstrate the system transonically and measure droplet size distribution, droplet speed and liquid water content in the speed range Mach number 0.3 - 0.9. The measured droplet size spectra will be compared against measured rainfall spectra. Lastly, the system which will be developed and demonstrated is expandable to facilities where large components can be tested.