In the placement of vertical axis wind turbines, trees are a constant presence in the vicinity. They are found to grow at different height and shape configurations. And in areas such as the Minnesota State University, Mankato (MNSU) campus, they serve as blockage to airflow; limiting the efficiency of installed turbines. This work sets the precedent for the validation of vegetative numerical models created for the Xcel Energy Research Development Fund (RDF) project.
Using two-dimensional (2-D) numerical simulations of porous cylinders placed in a rectangular medium of air, insight into the flow profile and distribution in the leeward side of the cylinder is gained. Mesh and turbulence intensity dependency test show less than 5% change in flow properties. Domain size and blockage ratio remained an important factor to consider during this simulation.
In this work, a numerical investigation was performed using design of experiment (DOE) principles, atmospheric flow and VAWT performance criteria to vary the incoming velocity and porosity to observe the effect on the wake velocity characteristics. It was observed that for inertial resistance coefficients greater than 200 m-1, the porous cylinder behaves as an impermeable object limiting the flow of air through the porous zone.
Following the qualitative descriptions of the porous flow regime, comparisons are made with 2-D results from existing literature. For velocity, there is strong agreement with trend of the non-dimensional velocity flow along the centerline. However, the results from the pressure distribution and the turbulent properties are underestimated when compared due to the presence of enstrophy in 3-D flow. Using actuator disk theory and leaky Rankine bodies, the resulting velocity field is used to obtain an estimate of source and sink strength ratios for use in flow field estimation.
Date of Degree
Master of Science (MS)
Mechanical and Civil Engineering
Science, Engineering and Technology
Bassey, D.C. (2019). Employing 2-D CFD & LRB model around trees to improve VAWT placement [Master's alternative plan paper, Minnesota State University, Mankato]. Cornerstone: A Collection of Scholarly and Creative Works for Minnesota State University, Mankato. https://cornerstone.lib.mnsu.edu/etds/949/
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