Prediction of Yawing Moment for a Hand-Launched UAV Considering Interference Effect of Propeller Wake

In this paper, three-dimensional unsteady computational fluid dynamic(CFD) analyses based on overset grid technique have been performed for a hand-launched unmanned aerial vehicle(UAV) considering the wake effect generated by a rotating propeller. In addition, the defection of rudder is considered in order to consider to predict the equilibrium condition of yawing moment during cruise flight conditions. It is importantly shown in this paper that the wake interference effect of the propeller is significant to accurately predict the yawing moment of the UAV and the yawing moment coefficient corresponding to a flight speed can be different because of its different amount of wake effect due to the different rotating speed of the propeller.

Effects of the Advance Ratio on the Evolution of Propeller Wake

This study numerically carried out the propeller open water test (POW) by solving Navier-Stokes equations governing the three-dimensional unsteady incompressible viscous flow with the turbulence closure model of the Κ-ω SST model. Numerical simulations were performed at wide range of advance ratios. A great difference of velocity magnitude between the inner region and the outer region of the slipstream tube forms the thick and large velocity gradient which originates from the propeller tip and develops along the downstream. Eventually, the strong shear layer appears and plays the role of the slipstream boundary. As the advance ratio increases, the vortical structures originated from the propeller tips quickly decay. The contraction of the vortices trace is considerable with decreasing the advance ratio.

Wake optimization of ducted propeller

Object and purpose of research. This paper discusses marine ducted propeller and the ways to ensure its target performance parameters. The purpose of this study was to mitigate unsteady forces on the propeller behind the duct struts. Materials and methods. Analytical estimates of propeller parameters and in-house KSRC methods for numerical simulation of ducted propeller behaviour. Main results. Calculations of effective wake behind duct struts taking into account the flow around hull and its append-ages. Calculations of unsteady forces for a standard propeller operating in this wake. Design of a propeller with increased blade skew. Calculations of unsteady forces for the new propeller in the initial wake. Wake field parameters contributing to mitigation of unsteady forces. Calculations for the new strut shape for wake optimization. Calculations of unsteady force amplitudes for standard propeller in the new wake. Conclusion. Ducted propeller discussed in this study was meant to illustrate how propeller wake properties, like unsteady forces, can be optimized without changing propeller geometry, only by means of curved duct struts.

Numerical Investigation of Unsteady Cavitation Flow around E779A Propeller in a Nonuniform Wake with an Insight on How Cavitation Influences Vortex

In the current study, the turbulent cavitation flow around a marine propeller in a nonuniform wake is simulated with the shear stress transport (k−ω SST) turbulence model combining Zwart–Gerber–Belamri (ZGB) cavitation model. The predicted cavity evolution shows a fairly well agreement with the available experimental results. Important mechanisms of propeller cavitation flow, including side-entrant jet and cavitation-vortex interaction, are analyzed in this paper. Vorticity is found to be mainly located in cavitation regions and the propeller wake during propeller rotating. The unsteady behavior of cavitation and side-entrant jet can both promote local vorticity generation and flow unsteadiness. In addition, it is indicated with the relative vorticity transport equation that the stretching term plays a major role in vorticity transportation, while baroclinic torque and Coriolis force term mainly influence the vorticity distribution along the liquid-vapor interface.

Sound Field Properties of Non-Cavitating Marine Propellers

The sound field properties of non-cavitating marine propellers are investigated using a hybrid method, in which the FWH (Ffowcs William-Hawkings) analogy is coupled with the BEM (Boundary Element Method) approach. The investigations include both the uniform and non-uniform inflow conditions. For both conditions, the dominant sound source terms and the decay rate of the noise with regard to the distance to propeller centre are investigated. The influence of the permeable surface dimensions in the permeable FWH approach on the hydroacoustic result is also investigated. To carry out the investigations, the formulation to calculate acoustic pressure generated by the propeller wake sheet is proposed for the first time. The issues associated to coupling permeable FWH approach and BEM are also discussed, including the fictitious volume flux problem and the consideration of the ship wake field. It was found that the influence of the permeable surface dimension is little for the 1st BPF (Blade Passage Frequency), but cannot be ignored for the 3rd BPF. In the uniform inflow situation the thickness terms are found to be dominant, while in the non-uniform inflow situation the loading terms are dominant.