Narrative: The proposed research program seeks to conduct a systematic study of the hydrodynamics of lifting solid particles in air drilling; the latter being the process of making bore holes (wells) by utilizing air as the circulating fluid for hole cleaning. Through multiphase hydrodynamic modeling, a predictive capability would be developed which could be utilized both in the design phase as well as the operational phase of air drilling. Numerical solutions of the model would serve as a basis for its validation since comparison can be made with experimental data obtained. Not only would the result of this study foster a better understanding of the hydrodynamics of the system, but equally important is its impact in the optimization of air drilling which could result in substantial savings in drilling costs. Furthermore, it would reduce the uncertainties currently involved in the air drilling design which is based on rules-of-thumb and trial-and-error approaches. These would serve to encourage greater utilization of this technology which would eliminate some of the environmental problems associated with traditional drilling methods.