Common Envelope Wind Tunnel: Coefficients of Drag and Accretion in a Simplified Context for Studying Flows Around Objects Embedded Within Stellar Envelopes

摘要: This paper examines the properties of flows around objects embedded within common envelopes in simplified context a "wind tunnel." We establish characteristic relationships between key envelope flow parameters like Mach number and density scale height. Our wind tunnel is three-dimensional, cartesian geometry hydrodynamic simulation setup that includes gravity primary secondary stars allows us to study coefficients drag accretion experienced by object. Accretion lead transformation an object its orbit during phase. present two suites simulations spanning range gradients numbers -- relevant for near limb stellar deep interior. In one suite, we adopt ideal gas adiabatic exponent $\gamma=5/3$, other, $\gamma=4/3$. find rise with steeper are consistently higher more compressible, $\gamma=4/3$ flow. illustrate impact these newly derived integrating inspiral through $3M_\odot$ ($\gamma\approx5/3$) $80M_\odot$ ($\gamma\approx4/3$) giants. examples, relatively rapid initial because, limb, dynamical friction generated mainly from dense focussed deeper primary-star's envelope. timescale carries potential implications transients early interaction.