Accepting a Challenge - The Development of PIV for Application in pressurized cryogenic Wind Tunnels

Abstract

The development and application of a Stereo-PIV system in the cryogenic transonic wind tunnel ETW enabling detailed flow field analyses on scaled models of transport aircraft at flight Mach- and Reynolds numbers is described. The specific conditions in such wind tunnels as cryogenic gas temperatures down to 110 K and moderate gas pressures of up to 450kPa as well as a large plenum encapsulating the test section made specific developments necessary. This comprises the generation of suitable flow tracers for cryogenic flows considering the specific requirements for an application in the ETW as well as the supply of laser light of high pulse energy and optical components to be placed within the cryogenic environment. Optical effects due to gas density changes within the wind tunnel plenum and light beam deflections or shifts are considered in the optical design of the CRYO-PIV system. Following trials in the cryogenic research tunnel PETW the applicability of the developed system is successfully demonstrated in the ETW during two test campaigns for a full scale and a half- model of a transport aircraft. The employed Stereo-PIV system and first results of the measurements are discussed. Scheduled next steps for improvements based on the gained experiences are outlined.