Turbulent swirling flow in water model of a gas turbine combustor is computationally investigated. As the basic modeling strategy, a three-dimensional unsteady RANS approach is applied, employing a differential Reynolds stress turbulence model. A highly unsteady and three-dimensional flow structure, exhibiting vortex breakdown and a precessing vortex core is observed. For a better understanding and demonstrating the influence of different modeling approaches, computations are carried out for different modeling parameters, comparing their results. These include the solution domain definition, turbulence modeling, the time-step size and the time-averaging period.