Doctor of Philosophy
Civil and Environmental Engineering
The challenge in large scale experimental fluid dynamics comes from the demand to develop simple methods that can measure and model movement of flexible objects and wind flow over large three-dimensional volumes with readily available equipment. Representing and modelling the flow around trees is challenging mainly because of the complexity and variability of trees. In this research different methods were tested in the novel Wind Engineering Energy and Environment (WindEEE) Dome facility at Western University, Canada to capture displacements of a moving single tree and flow velocities over a model forest edge in a three-dimensional form. The tested measuring methods use commonly available optical equipment and require little or no calibration prior to the experiments. The correlation between the wind force exerted on a single garden tree canopy and the resulted projected area as well as between the wind force and the crown displacement were determined using an infrared time-of-flight camera. Two spatial components of wind flow velocity over a modelled forest were measured using a digital camera, light projectors and tracer particles. A three-dimensional - two components colored flow visualization technique is also investigated. The calculated horizontal and vertical flow velocity components were compared with data measured with Cobra probes. The flow is compared with Computational Fluid Dynamics (CFD) simulations and visualized in a three-dimensional form. The techniques prove to have a good accuracy, are easy to implement, are quantitative methods and come as an alternative to using complex laser-based measurement techniques.
Summary for Lay Audience
A challenge in experimental fluid dynamics is developing simple and accessible methods that can capture the wind flow components over large scale volumes and the three-dimensional displacements of flexible objects. Trees have been studied for different reasons from modelling risk of wind damage to trees to modelling wind flow over forests. Due to their complex and flexible geometry, it is challenging to describe the three-dimensional movement of the tree canopy with wind. Capturing and analyzing the flow over forests requires complex equipment and careful calibration. The main focus of the thesis was developing practical and easy to use methods for detecting moving bodies as well as extracting wind speeds over large volumes with application to tree measurements in wind tunnel facilities. The first technique used in this research work employs an infrared time-of-flight sensor which facilitates a better understanding of the behavior of a single tree crown against wind speed. The second method employs a digital camera, a white light projector and tracer particles over a model forest and allows for a rapid extraction of the vertical and horizontal wind components of the flow field. The third method adds color to the previous method to allow a three-dimensional visualization of the particles in the test volume.
Enus, Marilena, "New Experimental Methods For modelling Canopy Problems" (2021). Electronic Thesis and Dissertation Repository. 7625.