|Abstract:||A new transonic wind tunnel facility was designed and built on the University of Illinois at Urbana-Champaign campus to enhance testing capabilities of the transonic flow regime. The new tunnel will expand the experimental capabilities available to the Department of Aerospace Engineering at UIUC for studying and understanding topics such as compressible dynamic stall aerodynamics, shock buffet phenomenon and control, shock wave boundary layer ingestion to a propulsor, and other future research topics.
The new wind tunnel is a rectangular testing facility with a 6 in (width) x 9 in (height) cross-sectional area in the test section. It is a continuous, open-return facility, capable of operating within a Mach number range of M=0-0.8, and possibly reaching M=0.85 or higher depending on the test section configuration. The wind tunnel was assembled and installed in the Aerodynamics Research Laboratory. The tunnel is driven by a centrifugal blower that exhausts the air back into the laboratory. The components designed for the tunnel were the nozzle, diffuser, test section, settling chamber, inlet flow conditioning section, and the structural assembly.
The most significant challenges in the design and development of the tunnel were enveloped in the test section and suction plenum control system. When performing experiments on transonic aerodynamic bodies, if the Mach number is high enough, pockets of locally supersonic flow will be seen in the test section. Therefore, to simulate unbounded transonic flight, partially-open test section walls were implemented to prevent shock reflections and test section choking. The suction across these walls was controlled by flaps at the aft end of the test section. The pressure differential created across the open-area walls can cause vibrational issues if adequate suction is not provided and unloaded into the diffuser via control flaps. For this reason, thicker open-area walls were substituted after the testing with thinner walls experienced these undesirable vibrations.