In the field of astrophysics, the term hydrodynamics is commonly used for fluid dynamics, the study of forces and motion in bodies of liquids or gases. In some scientific/engineering fields, the term is used more specifically to refer to the dynamics of non-compressible fluids, i.e., liquids, reserving the term aerodynamics for the dynamics of gases. (In astrophysics, there do exist circumstances where the formulae for non-compressible fluids are useful approximations of the dynamics of gases.) A simulation of fluid flows (hydrodynamic model or hydrodynamical model) can be used for modeling Earth oceans or atmosphere, or the same for atmospheres of astronomical bodies.
Magnetohydrodynamics (MHD) is the study of electrically conducting fluids (either liquid or gas) in motion and their interaction with coincident electric and magnetic fields. Other subclasses of hydrodynamics:
Such additional factors are significant in some situations, such as modeling supernovae.