Flow measurement around a cycloidal propeller

Abstract

An experimental investigation was conducted to study the flow around a cycloidal propeller. Flow fields were obtained using a particle image velocimetry system whose data acquisition was synchronized with the propeller's angular position. The chord-based Reynolds number was Re c = u r c/t = 1.4 9 10 4 , where u r is the rotational velocity of the propeller and c is the chord length of the airfoil. Flow characteristics such as mean velocity, vorticity and the RMS value of velocity fluctuation were derived from the measurements. The results demonstrated the presence of a downwash around the propeller during the generation of lift. Detailed observations around each airfoil visualized distinct vortex shedding and reattaching flow at certain phase angles of the propeller.

Analytical modeling of a cyclorotor in hovering state

“…In this particular situation the pitch angle becomes constant and the thrust generated, predicted by the analytical model, is always zero. This result is similar to the one presented in Nakaie et al 25 In both results, analytic and experimental, the power is not zero, because the rotor must overcome the profile drag, even if not providing thrust. For this case, Figure 28 shows the pitch angle and the blades' configuration, for zero thrust, predicted by our analytical model using Bosch rotor geometry definition.…”

“…As one can see through Figure 1, the blades on the cyclorotor have no sweep angle. In this way, the equation for 3-D lift curve slope reduces to equation (25).…”

“…24 This flowfield behavior has recently been confirmed by experimental testing using particle image velocimetry (PIV). 25 In following paper it is proposed a new semiempirical model for predicting the thrust generated and power is required by the cycloidal rotor. The models are devised using an empirical parameter but includes first principles theory in order to account for the effects of unsteady aerodynamics.…”

“…24 This flowfield behavior has recently been confirmed by experimental testing using particle image velocimetry (PIV). 25

Figure 1.Three-dimensional representation of a cyclorotor.

Figure 2.Possible air-vehicle operating with a cyclorotor.

Figure 3.Pitch mechanic control system.

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Parametric Analysis of a Large-Scale Cycloidal Rotor in Hovering Conditions

“…Such an interaction may improve the rotor thrust generation by delaying stall on each individual blade (Páscoa and Ilieva 2012;Yu et al 2013) but it can also reduce their efficiency (Xisto et al 2014b). The flow on the cyclogyro was also analysed using experimental PIV (Particle Image Velocimetry) techniques, where complex flow patterns were observed, like the formation and convection of the leading edge vortex on the pitching aerofoils (Benedict et al 2010b), the generation of large regions of rotating flow inside the rotor cage and a skewed exit flow (Benedict et al 2010a;Nakaie et al 2010).…”