Numerical Optimization and Experimental Validation of a Low-Speed Wind Tunnel Contraction

A low-speed wind tunnel is developed for fluid dynamics research at Reykjavik University. The tunnel is designed for conducting research on the flow past micro air vehicles, as well as fundamental research on turbulence. High flow quality is elemental for both research projects. The tunnel is of open suction type and is composed of a square inlet with a honeycomb and turbulence screens, settling chamber, contraction, experimental section housing, diffuser, and axial fan. Here, we describe the details of the design optimization procedure of the contraction, which is a key to getting a high quality flow in the experimental section. A high-fidelity computational fluid dynamic (CFD) flow solver is used to capture the nonlinear flow physics. Due to the high computational cost of the CFD simulations, surrogate-based optimization (SBO) is used to accelerate the design process. The SBO approach replaces direct optimization of the high-fidelity (accurate but computationally expensive) model by iterative optimization of a properly corrected low-fidelity model obtained from low-fidelity CFD simulations. The optimum contraction design is verified using high-fidelity CFD simulation, as well as by experimental measurements.