Open Circuit/Eiffel-Type Subsonic Low Speed Wind Tunnel (LSWT) Conceptual Design Initial Parameters and Section Losses' Analysis for the Selection of an Adequate and Efficient Axial Fan

In aerospace, the study of airflow around bodies of different shapes is critical when investigating aerodynamic design in different flow regimes based on the similarity parameters, primarily: Reynold's Number (Re) and Mach Number (M). Thus, it is necessary to have a means to experimentally downsize controlled conditions of airflow that is geometrically and aerodynamically similar to a real life condition. This can be accomplished using a wind tunnel. In this case, Don Bosco University (UDB) in El Salvador has taken the development and promotion of STEM careers and educational innovation in aerospace Engineering and Technology advancements through the design of a low-speed subsonic wind tunnel (LSWT). Due to the costs and simplicity of manufacturing, a simpler yet effective linear or Eiffel- type design was envisioned for experimentation by students and researchers. To design the geometry of a wind tunnel with specifications of a Mach number of M=0.21-0.22, new methodologies were used including: iterative methodology of parameterized geometry-specified, user-controller parameters in SolidWorks® CAD software for the initial drawings and general layout, a flow analysis of power required according to the pressure losses. Therefore, this document presents the results of a computational methodology developed in Microsoft Office 365 Excel® to iterate the different geometric parameters of each section of the LSWT according to previous studies and numerical and quantitative analyses to determine a general loss coefficient, which can later be used to select am appropriate axial fan that meets the requirements defined by the designer to achieve flow conditions in the test section. According to the iterative analyzes carried out, the section of the tunnel that experiences the greatest loss coefficient and adverse pressure is the main diffuser with a selected length of 5.0 m according to the most efficient energy ratio vs. manufacturing cost-balance. The test section has a double-symmetrical square shape cross section with a height and width of 0.60 m. At the end of the analysis, a tunnel with length of 10.80m was obtained, with a total loss coefficient of 0.158668 and a required flow power of 18.62HP for the desired conditions and a selected 50HP axial fan.