Design, implementation and validation of a flow management device for multi-fan wind facilities

Although multi-fan wind facilities can generate a wide range of flow configurations, from steady and uniform to unsteady shear and turbulent flows, iterative procedures and flow characterization are required for control. To simplify the control problem, the design of a novel flow management device architecture is discussed. The jets issuing from the inlet fans are independent of each other and flow uniformity is achieved through mesh screens, with the effect quantified by an inviscid flow model. It is shown that the downstream flow quality depends on the momentum thickness of the boundary layers issuing from the device walls and the evolution of the momentum thickness was predicted using a boundary layer model modified to include screens. The model was validated experimentally using PIV. A configuration with one honeycomb and 4 stainless steel mesh screens was installed on a facility with test section of 48 cm by 48 cm and characterized using PIV and hot wire anemometry. Flow non-uniformity levels <3% and turbulence levels <0.5% (unfiltered) were obtained in the range 1-11 m/s. The validated flow uniformity and boundary layer models can guide the design of flow management devices for multi-fan wind facilities of any size.