Leading Edge Bumps In Ventilation Fan

We report on a numerical study on the performance of an innovative axial flow fan for large tunnel ventilation. Taking a lead from a previous biomimetic analysis on the performance of the flippers of the humpback whale, this whale-fan was designed with sinusoidal-like leading edge that mimic the tubercles of the whale. We found that this provided a resistance to stall and improved lift recovery in post-stall operations. The sinusoidal profile of the leading edge allowed to control the distribution of vorticity on the suction surface of the blades and increase the stall margin of the device. The paper discusses the design methodology that was followed to correlate the sinusoidal shape of the leading edge of the blade with the desired vorticity distribution at the trailing edge that was needed to control separation. In the paper we show the results of numerical computations carried out with the finite volume open-source code Open FOAM on the whale-fan as well as a baseline fan with straight leading edge. Reynolds Averaged Navier-Stokes equations for incompressible flow were solved with a nonlinear (cubic) eddy-viscosity k-ε model that was found able to control the eddy viscosity distribution in order to account for anisotropy of Reynolds stresses and better reproduce the three-dimensional properties of the flow field. The paper shows the performance chart of the whale-fan, derived from numerical computations, and gives an insight of the fluid flow mechanisms that are generated by the sinusoidal leading edge on the suction surface of the fan. A comparison with the baseline fan with straight leading edge is provided in order to highlight how the shape of the leading edges affect the performance of the fan. Copyright © 2013 by ASME.