Theoretical and computational studies on the important classic problem of the dynamics of galactic gas flows and the roles played by the gas in the structure and dynamics of galaxies will be carried out. Normal and barred spiral galaxies will be a major focus of the research of the wealth of improved and detailed observational data that has become available in recent years, now making possible new definitive tests and comparisons with observations. Cloud-particle galactic gas dynamics and continuum gas dynamics are essential in the multipronged program of research. Detailed simulations of full galactic disks and higher resolution simulations of selected local regions will be studied in parallel to better understand the relationship between grand design and local spiral arm morphologies. The effects of self gravitation among clouds, magnetic field interactions, and star formation processes will also be primary areas of focus. The local effective viscosity of the cloud is determined from the cloud-particle simulations and used to produce a generalized continuum gas dynamical description of galactic gas flows that properly simulates the average transport properties of the cloudy interstellar medium (ISM). The utilization of computational simulation in this work is a topic of great significance at the present time and is a separate major thrust area. The high spatial resolution of the simulations will be utilized to make definitive comparisons with observations and provide careful tests for theoretical predictions based on local stability analyses.
