Effects of Various Air Flow Modification Techniques on Design and Development of a Multi-fan Blower Type Open-Section Civil Wind Tunnel

Abstract

Abstract The wind tunnel is widely used as an efficient and effective tool for conducting aerodynamic and civil engineering research. This study focuses on the design, construction, and analysis of the results of an open-circuit wind tunnel specifically designed for civil engineering purposes in the Civil Engineering Department of KNT University of Technology in Iran. The wind tunnel has a 2.9 x 4.3 meters cross-section in the downstream open section and is equipped with six fans upstream. These fans are driven by a 1440 rpm engine with a power of 30 kW (40 hp). One crucial aspect of wind tunnel design is controlling turbulence and creating a uniform flow in the test section while minimizing the reduction in airflow velocity. To improve the airflow velocity, reduce the turbulent intensity, and optimize the wind tunnel's output parameters (such as distributions, turbulent intensity, and airflow velocity), various equipment was added to the upstream and downstream of the airflow generating conduit. This equipment includes proper bell-mouth intakes, electromotor, propeller caps, multiple honeycombs (with coarse and fine sizes at sequential positions), and wire mesh inside the diffuser and main tunnel. The effect of each of these components on the airflow parameters was evaluated through tests conducted at three different engine speeds: 600, 1000, and 1200 rpm. Airflow velocity Cartesian components measurements in the test section were obtained using a hot wire flowmeter and a differential pressure sensor. The results indicate that installing such equipment sets significantly improved the flow uniformity in the test section. It reduced the average turbulence intensity by 15%, 42%, and 42% for propeller rotation speeds of 600, 1000, and 1200 RPM, respectively. This improvement was achieved with only a 21%, 23%, and 12% reduction in airflow velocity. Additionally, the uniform air velocity distribution parameters within the downstream section of the flow were improved by approximately 55% and 25%, respectively.