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September 17, 2012

Using stereo particle image velocimetry in algae raceway

Name: Blake Lance
Major: Mechanical engineering
Department: MAE
Graduation date: Fall 2012 (MS)
Title: Using stereo particle image velocimetry to quantify and optimize mixing in an algae raceway using delta wings

Biofuel research has been continually growing over the past six decades. Of the potential sources for biofuels, microalgae is the most promising, and circulating (raceway) ponds are the most cost-effective method for growing microalgae in abundance. Nevertheless, biofuel production from algae must be more efficient to be competitive with traditional fuels. Previous studies using several airfoils, triangles, and squares at high angles to the flow direction (angle of attack) show an increase in mixing in raceways and can improve productivity by up to a factor of 2.2. Researchers show that increasing growth by increasing mixing is a repeatable effect that is desirable to both reduce operation costs and increase production. An experimental raceway of similar shape to commercial facilities is constructed to test the effect of a delta wing (DW) on fluid motion in the laboratory using fresh-water. The DW is a triangle made of plate material that is placed in the circulating flow creating significant fluid circulation. Results from this investigation can be scaled to larger growth facilities use arrays of DWs. Stereo particle image velocimetry (PIV) is used to measure and optimize the use of DWs as a means to increase fluid mixing. Three studies are performed to determine the best fluid speed, angle of attack, and DW spacing in the raceway based on mixing. Two new mixing quantities are defined to reduce results for optimization. These studies result in the optimal use of DWs in raceway ponds to increase mixing and are expected to increase growth.