Development of a Supercooled Large Droplet Environment within the NRC Altitude Icing Wind Tunnel 2015-01-2092
Simulations of supercooled large droplet (SLD) icing environments within the NRC's Altitude Icing Wind Tunnel (AIWT) have been performed in which broad band mass distribution spectra are achieved that include a distinct pattern of liquid water content (LWC) over a range of droplet sizes (i.e., bi-modal distribution). The mass distribution is achieved through modification of the existing spray system of the AIWT to allow two spray profiles with differing LWC and median volumetric diameter (MVD) to be simultaneously injected into the flow.
Results of spray profile distributions measured in the test section have demonstrated that freezing drizzle conditions, where MVD is either less than or greater than 40 μm, can be achieved. Work performed to provide freezing rain conditions is also discussed and highlights the challenges of providing this environment as a result of limitations of the spray system in providing the large droplet sizes (up to 1 mm diameter) or where gravitational settling of these larger drops prevents them from reaching the test section.