Results Summary and Images Data Analysis The control school bus model had a higher C D than theoretically expected; compared to a theoretical This could be due to two reasons: the model made in Autodesk Simulation CFD was fairly coarse to reduce the mesh complexity and sharp edges tend to cause more flow separation and higher pressures than smoother ones found on a real bus. Secondly, CFD comes with inherent error that was made worse with the relatively low mesh resolutions(~ k elements) due to limited computing power. Despite this, it is still viable to make comparisons between the control and the three designs. The rear spoiler, even though it decreased the size of the wake, added an extra 1.267m^2 to the cross sectional area and increased overall drag force. A cost analysis was not done for it because the design did not reduce drag. All the frontal fairing designs reduced F d by a considerable amount. The worst performing, as expected, was the flat design. All the other designs were fairly similar in their %DeltaC d /Volume scores, showing that they were fairly close in efficiency. The most efficient design with the 175cm arc radius reduced F d and C d by % and had a materials payback period of years if made with 0.5cm polycarbonate and years if made with 0.5cm polypropylene, both reinforced with 30% glass fiber. The back plates were all fairly effective in reducing F d and C d. From the first optimization, The efficiency, measured through negative %DeltaC d /Volume, constantly increased as length decreases. 0.3m was the smallest plate size for practical reasons. In the 2nd round of optimization, the most efficient yaw angle was 30 degrees, with the efficiency decreasing as angle increased or decreased. The back plate design was also successful, with a payback period of years for the aluminum design and years for the steel. Fd(N)Cd%Delta CdFyCl Volume Device(cm^3)%DeltaCd/Volume Rear Spoiler Not FeasibleNA Fd(N)Cd%Delta CdFyCl Control Bus Fd(N)Cd%Delta CdFyCl Volume Device(cm^3) %DeltaCd/Volum e Bus Back Plates – Default Bus Back Plates - Extra horizontal flat plate Bus Back Plate - Curved Boat-Tail Design and Optimization of a Drag-Reduction Add-On Device for a School Bus Back Plates Fd(N)Cd%Delta CdFyCl Volume Device(cm^3) %DeltaCd/Volume (m^3) Straight Arc radius Arc radius Arc radius Arc radius Control Spoiler Fairing Volume Mesh Cross Section Mesh Frontal Pressure: Fairing vs. Control Control Fairing Rear Pressure: Control vs. Plates Control Back Plates Velocity Distribution Control Back Plates Fairing Recirculation Control Fairing Back Plates Jiedong Duan Niles North High School