How Can CFD Predict Airflow and Object Trajectories Around Vehicles?

[spiderB]

Trying to evaluate airflow around a vehicle and behind it to calculate where an object would rest after leaving driver side window.

 

[Baluncore]

Welcome to PF.
It will depend on the shape and speed of the vehicle, and the characteristics of the object and the launch trajectory.
If you carry out the practical experiment you may be charged with littering.
Have you considered building a wind tunnel ?
Consider also; http://en.wikipedia.org/wiki/Finite_element_method

 

[B0b-A]

wikipedia.org/wiki/Computational_fluid_dynamics

CFD ... Free_and_open-source_software