Numerical study of the reduction of the local resistance coefficient of a tee for flow separation

Introduction. In modern construction, mechanical ventilation systems are becoming increasingly popular. Given the high-pressure losses in the shaped elements of ventilation systems, it is necessary to improve their design geometry. This is especially true for supply ventilation system tees, where flow separation occurs, leading to significant energy losses due to flow deformation. The aim of the study is to numerically simulate air flow in a symmetrical square-section supply tee to determine the local resistance coefficient, to determine the contours of vortex zones at the point of air flow separation and the local resistance coefficient of an optimized supply tee constructed taking into account the contour of the vortex zone in the flow
deformation area.

Materials and methods. The pressure loss coefficient of a standard symmetric supply-air tee, the area of vortex zone formed in the flow separation region, and the pressure loss of an optimized tee were investigated using computational fluid dynamics (CFD) in COMSOL Multiphysics 5.6. The Reynolds-averaged continuity and Navier – Stokes equations were solved with the standard k–ε turbulence model incorporating wall functions.

Results. The value of the pressure loss coefficient of a standard tee showed close agreement with previously published data. The tee construction was optimized with consideration of the vortex zone in the deformation region by rounding the wall, with subsequent numerical investigation.

Conclusions. The study demonstrated that rounding the wall in the flow deformation zone of a standard supply-air duct tee reduces hydraulic resistance by 11.9 %. The results contribute to both scientific understanding and practical applications in the development of optimized tee.

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