Aerodynamic Study of Bulk Commodity Tractor Trailers

Our project goal is to test aerodynamic features of four existing tractor trailers in order to reduce emissions. This will be accomplished by studying and comparing the drag coefficients of each design. Our designs will be created with either 3D printing and/or laser cutting technology.

Problem Definition
Semi-trucks are used all over the world for transporting goods. They provide easy and affordable methods to keep economies running. The downside is that semi-trucks produce a lot of carbon-dioxide pollution from their exhaust. If the trailers they tow are improved aerodynamically, that carbon-dioxide production can be minimized. Western Trailer Company, headquartered in Boise, ID, has four main tractor trailer models, which are a flat-floor trailer, drop-center trailer, hopper trailer, and pup trailer. The Trailer Park Boys are tasked with testing and simulating these models in various configurations so improvements can be made to meet new tractor trailer requirements that will be implemented in 2018.

Design Goals & Deliverables
At the end of the project, the client will receive:

•	Scale models of selected Western Trailer products suitable for testing in the ME Wind Tunnel

•	Wind Tunnel data on aerodynamic drag associated with different scale models at different wind speeds

•	Methodology for translating changes in scale model drag coefficients to changes in fuel efficiency and emissions for full-size trailers (following appropriate federal guidelines)

•	Quantify changes in trailer performance associated with changes in trailer geometry for specific trailer models

•	Final design report that documents the team’s model development and testing process

Designs to be Tested
The existing tractor trailers are:

Testing Results
The coefficient of drag of the nose cone model does not differ by much from the base model.

We would like to run at higher speeds to see if a larger difference in drag coefficient shows up.

We still need to correlate our drag coefficients with full-size trailer drag coefficients.

Wind Tunnel Learning
When testing scale models, geometric similitude is very important.

The ratio of model length to actual length must be identical with model width to actual width, and so on with all other dimensions.

The Buckingham-pi theorem allows dimensional analysis to simplify testing and data processing.