Numerical and experimental investigation into effects of winglet shape on flow and noise performances of axial-flow fans for outdoor unit of air conditioner

•The effects of winglet shape on the performances of axial-flow fans (AFFs) are investigated.•The effects are quantitatively associated with the coherent structure of tip and leakage vortices.•The winglet in the gap flow region increases the leakage vortex strength.•The stronger leakage vortex adversely affected the flow and noise performances of the AFFs.