Study on the collision probability of vertical risers considering the wake interference effect

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

Journal of the Korea Institute of Military Science and Technology ◽

10.9766/kimst.2021.24.4.426 ◽

2021 ◽

Vol 24 (4) ◽

pp. 426-434

Author(s):

Ji-Min Park ◽

Dong-Hyun Kim ◽

Hyung-Ju Park

Keyword(s):

Interference Effect ◽

Fluid Dynamic ◽

Three Dimensional ◽

Wake Effect ◽

Rotating Speed ◽

Propeller Wake ◽

Moment Coefficient ◽

Wake Interference ◽

Aerial Vehicle ◽

Cfd Analyses

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.

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Wake Shielding Model Effect on Riser Dynamic Response

Volume 3B: Structures, Safety and Reliability ◽

10.1115/omae2017-62557 ◽

2017 ◽

Author(s):

Ping Fu ◽

Bernt J. Leira ◽

Dag Myrhaug

Keyword(s):

Dynamic Response ◽

Dynamic Analysis ◽

Interference Effect ◽

Flow Conditions ◽

Analysis Software ◽

Wake Interference ◽

Flexible Risers ◽

Wake Model ◽

A Current ◽

Steep Wave

The paper provides a method to estimate the clearance between two flexible risers in tandem arrangement by taking into account the wake interference when subjected to a combined current plus waves flow. The wake interference of a pair of risers due to current is studied by combining the results from global riser analysis software Riflex and Blevin’s wake model [1]. The deflection shapes of a pair of tandem risers with steep-wave configuration, with and without wake interference, are presented and discussed. The effect of the wake interference on dynamic response of a pair of 2D cylinders due to a current plus waves flow is investigated by assuming that the Blevins’ wake model, originally established for cylinders in steady flow, to be valid for current plus waves as well as current-dominant flow conditions. A simplified clearance assessment is also proposed by which a static wake interference effect is considered during the dynamic analysis, and comparisons are made between the two methods.

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Main Rotor Wake Interference Effects on Tail Rotor Thrust in Crosswind

International Journal of Aerospace Engineering ◽

10.1155/2021/9994115 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Chang Wang ◽

Min Qi Huang ◽

Shuai Ma ◽

Hao Wen Wang ◽

Min Tang

Keyword(s):

Interference Effect ◽

Cfd Simulation ◽

Dynamic Pressure ◽

Leading Edge ◽

Strategy Development ◽

Potential Hazard ◽

Main Rotor ◽

High Position ◽

Wind Speeds ◽

Wake Interference

Reverse pedal operational property in front crosswind flight condition is a potential hazard for accidents involving loss of tail rotor effectiveness (LTE), which is closely related to the main rotor (MR) wake interference on the tail rotor (TR). As understanding of this interaction is vital for the early warning strategy development, the MR wake influence effect on TR thrust and the effect of helicopter yaw stability are examined in this study. For this purpose, the comparison of TR thrust and flow field with wind azimuth and speed in front crosswind environment was performed by experiment and CFD simulation, respectively. Test campaign was performed at a 5.5 m × 4 m wind tunnel in the China Aerodynamics Research and Development Center using a high-position bottom-blade forward-rotating TR and a counterclockwise rotating MR to address the TR thrust under wind speeds of 8–22 m/s with 50°, 60°, and 70° wind azimuths. The influence of MR disc loading was also contrasted. CFD analysis was used to gain insight into the flow physics responsible for the interference effect. It was conducted with unsteady Reynolds-averaged Navier–Stokes simulations, where the MR using the actuator disk approach and the TR blade rotation was modeled via a sliding mesh method. Results indicated that the MR disc vortex has a remarkable interference effect on the TR aerodynamic performance characteristic and that the effect is sensitive to the wind speed, wind direction, and MR disc loading. The observed yaw instability is considered to be related to the lesser inflow introduced by the MR disc vortex due to the change in the relative position of the disc vortex filament and TR with the wind azimuth. The increase in TR thrust at moderate wind speeds is due to the increase in leading edge dynamic pressure caused by the opposite swirl direction of the disc vortex contrasted to the TR. The MR disc loading affects the TR thrust due to the change of disc vortex strength and position.

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