Design and experimental evaluation of an open-section compact multi-fan wind tunnel

Abstract Compact multi-fan wind tunnels are increasingly used for engineering and environmental studies where laboratory space is limited. However, achieving acceptable flow quality in such facilities remains challenging due to elevated turbulence intensity and velocity non-uniformity caused by fan–fan interactions and short flow-conditioning lengths. This study presents the design, construction, and experimental evaluation of an open-section compact multi-fan blower wind tunnel with an overall length of less than 8 m and a test section measuring 4.2 m × 2.8 m. Rather than applying a formal mathematical optimization algorithm, flow quality was improved through an iterative, engineering-driven refinement of key geometric and flow-conditioning elements. Successive design modifications—including bell-mouth intakes, fan caps, honeycomb structures, diffuser gratings, and settling chamber extension—were systematically implemented and experimentally assessed. Flow performance was quantified using spatially resolved measurements of mean velocity, turbulence intensity, velocity non-uniformity, skewness, and kurtosis over a defined effective core region. Experiments conducted at fan rotational speeds of 600, 1000, and 1200 rpm demonstrate consistent improvements in flow quality. The combined flow-conditioning strategy reduced the spatially averaged turbulence intensity by approximately 21%, 44%, and 47% at the respective speeds, while maintaining test-section velocities of up to 10 m s −1 . The final configuration achieved an average turbulence intensity of approximately 18%–20% together with improved velocity uniformity and statistically balanced turbulence. The results demonstrate that effective flow homogenization can be achieved in compact multi-fan wind tunnels without long settling chambers or contraction nozzles, making the proposed facility suitable for structural wind loading and environmental flow simulations under space and budget constraints.