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We study mass ejection from accretion disks formed in the merger of a whitedwarf with a neutron star or black hole. These disks are mostlyradiatively-inefficient and support nuclear fusion reactions, with ensuingoutflows and electromagnetic transients. Here we perform time-dependent,axisymmetric hydrodynamic simulations of these disks including a physicalequation of state, viscous angular momentum transport, a coupled $19$-isotopenuclear network, and self-gravity. We find no detonations in any of theconfigurations studied. Our global models extend from the central object toradii much larger than the disk. We evolve these global models for severalorbits, as well as alternate versions with an excised inner boundary to muchlonger times. We obtain robust outflows, with a broad velocity distribution inthe range $10^2-10^4$ km s$^{-1}$. The outflow composition is mostly that ofthe initial white dwarf, with burning products mixed in at the $\lesssim10-30\%$ level by mass, including up to $\sim 10^{-2}M_\odot$ of ${}^{56}$Ni.These heavier elements (plus ${}^{4}$He) are ejected within $\lesssim 40^\circ$of the rotation axis, and should have higher average velocities than thelighter elements that make up the white dwarf. These results are in broadagreement with previous one- and two-dimensional studies, and point to thesesystems as progenitors of rapidly-rising ($\sim $ few day) transients. Ifaccretion onto the central BH/NS powers a relativistic jet, these events couldbe accompanied by high energy transients with peak luminosities $\sim10^{47}-10^{50}$ erg s$^{-1}$ and peak durations of up to several minutes,possibly accounting for events like CDF-S XT2.

Nuclear Dominated Accretion Flows in Two Dimensions. II. Ejecta dynamics and nucleosynthesis for CO and ONe white dwarfs