Simulation-driven design of low-speed wind tunnel contraction

• Here, we present an optimization procedure for the design of low-speed wind tunnel contractions using computationally expensive and accurate CFD models.
• The approach is surrogate-based and uses variable–fidelity models to reduce the computational burden.
• An optimized contraction design is presented and verified using a high-fidelity CFD model.
• The optimized wind tunnel was fabricated and the numerical results are further verified by experimental measurements.

A low-speed wind tunnel is developed for conducting research on the flow past micro air vehicles. 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. In this paper, we describe the details of the design optimization procedure of the contraction, which is 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 expense 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. Here, we exploit variable–fidelity CFD simulations, as well as a simple multiplicative response correction technique to construct the surrogate model of the wind tunnel contraction, allowing us to optimize its shape at a low computational cost. To our knowledge, it is the first application of variable–fidelity surrogate modeling to wind tunnel contraction design. The optimum nozzle design is verified using a high-fidelity CFD simulation, as well as by experimental measurements of the fabricated wind tunnel. Experimental validation confirms the correctness of the numerical optimization procedures utilized to design the contraction.