Clumpy-gas radiation hydrodynamics: Formulation

Abstract Various astrophysical outflows from luminous active objects are supposed to be inhomogeneous in either form porous or clumpy. We newly construct the basic equations describing clumpy-gas radiation hydrodynamics (CRHD), where a lot of clumps/cloudlets coexist with the tenuous ambient gas. Both are affected by the radiative force from the luminous source, and interact with each other via the drag force due to ram pressure. Since the radiative force acting on the clump is smaller than that on the ambient gas, clumps are generally less accelerated in winds/outflows. Furthermore, as the optical depth of cloudlets becomes higher, the efficiency decreases. We present several simple applications, including a vertical flow, a spherical wind, spherical accretion, and a simple wave. Since the present formulation is the simplified one under the nonrelativisitc treatment, there is plenty of room for further development.