Propeller and inflow vortex interaction: vortex response and impact on the propeller performance

Abstract

The aerodynamic operating conditions of a propeller can include complex situations where vorticity from sources upstream can enter the propeller plane. In general, when the vorticity enters in a concentrated form of a vortex, the interaction between the vortex and blade is referred to as blade-vortex interaction or BVI. The interaction may affect the propeller performance as well as its noise production. In the present paper, investigations of the interaction of a wing tip vortex generated by a lifting surface upstream of the rotor plane and an eight-bladed propeller are reported. Utilizing two ends of an upstream wing with non-symmetrical airfoil, the rotation of the incoming vortex could be made to co-rotate or to contra-rotate with the propeller. The ensuing velocity fields were quantified with the help of particle image velocimetry (PIV), and the propeller performance was evaluated with the help of a rotating shaft balance (RSB) mounted on the propeller shaft. The results describe the displacement of the vortex core, as it moves through the rotor plane as well as the positive effect on the thrust and torque of the contra-rotating vortex and the opposite of it in the case of the co-rotating vortex. The current research could be applied to analyse the influence of the incoming vortex on the propeller, e.g., ground vortex, tip vortex shed from a control surface, etc. Keywords Vortex flow Á Blade vortex interaction List of symbols D Diameter of propeller, m J Advance ratio of propeller Q Torque of propeller, Nm Q C Torque coefficient R Radius of propeller, m T Thrust of propeller, N T C Thrust coefficient U eq Equilibrium inflow velocity of propeller, m/s U rad Radial velocity, m/s U tan Tangential velocity, m/s U ? Free stream velocity, m/s n Propeller rotating speed, round/s r À Vortex radius in front of the propeller disk, normalized by propeller radius r þ Vortex radius behind the propeller disk, normalized by propeller radius C imp,cor Circulation in the core of the wing tip vortex, normalized by U eq* D x Vorticity, rad/s

The numerical CFD investigation of hub losses of pushing air propellers with tandem joined blades of small sized unmanned aerial vehicles

“…The constants of the turbulent viscosity model are conventionally divided into two types; regular constants and the second type is a linear combination of constants for the k-ω and k-ε models. The combination is carried out using the function F 1 and equation (10). These constants are denoted by index 3 (for example, s k3 ) and are calculated by formula:…”

“…In the case of the use of tandem blades mounted on a common hub, an increased gradient of static pressure behind the rotor blades and the interaction of the first row of blades with the second are also added. When propellers are used on planes made according to the pulling pattern, the hub losses in the propeller itself are insignificant; however, losses are manifested when the tip and hub vortices interact with aerodynamic surfaces [9,10]. In the case of pushing propellers, losses must be estimated taking into account the flow around the hub and the propeller.…”

Analysis of quadcopter propeller vibration based on laser vibrometer

“…The propeller is rotating in a perpendicular plane to the laser vibrometer's beam, and thus the number of points achieved for each of the contours depends on the propeller's angular velocity and the data acquisition speed of the laser vibrometer. By using equation (1), the number of sample points read by the laser for a single rotation n t can be calculated based on the time needed for that rotation x 0 .…”

“…Propeller performance can be analyzed based on the impact of the airfoil vortex's response and material of the blades. 1,2 The elasticity of the material affects the blade's deformation during the rotation; a lighter material with higher elastic modulus is required to ensure that the impact of the airfoil vortex leads downward to obtain an optimal thrust value. Momentum and blade element theory [3][4][5] can be used in propeller's performance analysis.…”

Wind turbine wake vortex influence on safety of small rotorcraft

“…2(c). The orthogonal interaction was experimentally investigated using a propeller that was subjected to a wing tip vortex in the wind tunnel (17) . This problem was solved numerically, and results compared sufficiently well to the aforementioned experiment (18) .…”