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...

Evaluation and optimization of the control system of the Symphony Wave Power Device

Raising environmental concerns have stimulated the development of renewable energy, including energy from the oceans, which contain a huge potential. In this thesis, particular emphasis is given to wave energy, which can deliver up to 2 TW on a global scale. The aim of this thesis is to optimize the control system of the Symphony Wave Power...

A 19.8-mW Eddy-Current Displacement Sensor Interface with Sub-Nanometer Resolution

This paper presents an eddy-current sensor (ECS) interface intended for sub-nanometer (sub-nm) displacement sensing in hi-tech applications. The interface employs a 126-MHz excitation frequency to mitigate the skin effect, and achieve high resolution and stability. An efficient on-chip sensor offset compensation scheme is introduced which...

Simulations of steady and oscillating flow in diffusers

In this thesis diffuser performance will be simulated with computational fluid dynamics, which will be done with the program Ansys Fluent. The expanding geometry creates an adverse pressure gradient and under certain conditions there will also be separation.<br/><br/>At first a relative simple simulation will be done of a one-directional...

Drag and power-loss in rowing due to velocity fluctuations

The flow motions in the turbulent boundary layer between water and a rowing boat initiate a turbulent skin friction. Reducing this skin friction results in better rowing performances. A Taylor-Couette (TC) facility was used to verify the power losses due to velocity fluctuations P_V′ in relation to the total power, as a function of...

Oscillation and rotation of levitated liquid droplet

The oscillation and rotation of a levitated liquid droplet are simulated numerically using the level set method. The frequency and the damping of the oscillation for small amplitude are shown to agree well with those by the linear theory. It is shown that the oscillation frequency decreases as the amplitude increases. The oscillation frequency...

Sand Waves along the Dutch Coast

Sand waves, defined as longshore wave-like movements of the shoreline, measured in a horizontal plane, are described along several stretches of the shoreline of The Netherlands. They have a celerity in the order of 50-200 m/yr, a period of 50- 150 years and an amplitude of 30- 500 m. They are found along the whole Dutch shoreline. Analysis of...

The influence of Reynolds number on wave forces

Information, published to date, or. the effect of viscosity on wave forces is very indefinite. A series of experiments carried out in the Pulsating Water Tunnel at the Hydraulics Research Station Wallingford under closely, controlled conditions clearly defined the variation of primary forces with Reynolds Numbers up to 6 x 10 5 . Additionally...