Towards a Better Understanding of Attitude Oscillations Experienced by Quadcopters In Axial Descent

This study aims to quantify the aerodynamic behaviour of fixed pitch rotors with a diameter of 12.7 cm in axial descent, and its contribution to the attitude oscillations found for quadcopters under similar flight conditions. Wind tunnel tests are performed with an isolated rotor, as well as a complete quadcopter mounted inside a gimbal that...

Analysis the vortex ring state and propeller state of floating offshore wind turbines and verification of their prediction criteria by comparing with a CFD model

In our previous study, the vortex ring state (VRS) prediction criteria were introduced from helicopter's realm and applied to floating offshore wind turbines (FOWTs). The existence of the VRS on FOWTs was also successfully predicted. However, the prediction criteria we used have not been verified by comparing them with similar studies because...

The aerodynamics of floating offshore wind turbines in different working states during surge motion

The rotor of floating offshore wind turbines with platform motions may undergo different working states during its operation, e.g. from windmill working state to vortex ring and propeller working state. In this paper, an aerodynamic model based on a free wake vortex method is used to simulate the rotor undergoing surge motion. The associated...

CFD study of induction and finite blade effect on a floating horizontal-axis wind turbine

As the need for abundant and reliable renewable energy increases, there is a growing interest in floating wind turbines, which would allow to harness the wind resource in areas where bottom-founded wind turbines cannot be used. However, the movements of the platform are expected to cause unsteady aerodynamics effects, including different wake...

A free wake vortex model for floating wind turbine aerodynamics

In order to significantly increase the share of wind energy produced worldwide, wind energy technology is moving from onshore to offshore and from shallow water to deep water. Floating offshore wind turbines (FOWTs) are expected to be economically better than bottom-mounted turbines when placed in water deeper than 60 metres. Despite key...

Comparative analysis of different criteria for the prediction of vortex ring state of floating offshore wind turbines

The wind condition around floating offshore wind turbines (FOWTs) can be largely different from that developed around bottom-mounted wind turbines due to the platform motions. The existing literature identifies four working state of FOWTs, one of them being the vortex ring state (VRS) which may occur as the rotor moves in its own wake. It is...