The Truck Add-on Predictor applies OpenFOAM® computational fluid dynamics (CFD) to model the airflow over a joint vehicle and trailer body and the corresponding aerodynamic forces generated. The Truck Add-on Predictor uses a simple web portal user interface hosted at the Ohio Supercomputer Center (OSC). Simulation jobs run on a high performance computing cluster at OSC. The web portal allows you to configure, submit, and monitor simulation jobs and view the results. OpenFOAM is the industry-standard, open source CFD code developed and supported by the commercial company OpenCFD® Ltd. OpenFOAM is licensed under the GNU General Public Licence.