An isothermal computational study has been performed to study the impact of inlet boundary conditions on length of Internal Recirculation Zone (IRZ), velocity profiles, and swirling strength at various sections in a cylindrical furnace with tangential injections. The present work comprises modeling and simulation using Ansys platform considering air as a working fluid and employing the SST k-ω model for turbulence. Results show that swirling strength has a strong dependence on injection angle but has a rather weak dependence on the injection velocity. The mixing zone size varies remarkably across the range of injection velocities considered provided the injection angle is above 10°. Distribution of the swirling strength along with the furnace height downstream from the injection plane indicates rapid shoot up and gradual decrement.