The flow field in modern axial turbines is non-trivial and highly unsteady due to secondary flow and blade row interaction. In recent years, existing design-tools like two-dimensional flow solvers as well as fully three-dimensional CFD methods have been validated for the assumption of a quasi-steady flow field. Since the inevitable unsteadiness of the flow field has a direct impact on unsteady loss generation and work transfer, existing design methods stand in need of validation for local unsteady effects within the flow field. In order to clearly separate end-wall losses from those generated by blade row interaction within the blade passage, a two-dimensional core-flow is essential for the investigation. Hence, a new 1.5-stage high aspect ratio low pressure turbine has been designed to determine the intensity of core-flow blade row interaction for different axial gaps. First, inlet and outlet conditions of the test rig are evaluated with regard to homogeneity of the flow parameters in their radial and circumferential distributions. Secondly, the measurement data gained from rig tests have been applied as boundary conditions to time-averaged numerical computations. The flow field analysis for two different axial gaps focuses on the verification of the core flow. The authors show that the new turbine has been successfully verified using both test data and the numerical predictions, serving as a precondition for the validation of the numerical model for unsteady effects within the core-flow.