Flow within the space between the rotor and stator of a turbine disk, an area referred to as the rim seal cavity, develops azimuthal velocity component from the rotor disk. The fluid within develops unsteady structures that move at a fraction of the rotor speed. A measurement strategy is developed to measure the number of unsteady structures and the rotational speed at which they are moving in the rim seal cavity of an experimental turbine research rig. Data manipulation was developed to extract the speed and the numbers of structures present using two fast response aerodynamic probes measuring static pressure on the surface of the stator side rim seal cavity. A computational study is completed to compare measured results to a transient Unsteady Reynolds Averaged Navier-Stokes (URANS). The computational simulation domain consists of 8 vanes and 10 blades (the full test facility consisted of 29 vanes and 36 blades), carefully picked to reduce error caused by blade vane pitch mismatch and to allow for the structures to develop correctly, and the rim seal cavity to measure the speed and number of the structures. The experimental results found 15 structures moving at 77.5% of the rotor speed, computational results are based on the size of the domain and guidance from the experimental results found 14.5 structures are moving at 81.7% rotor speed. The agreement represents the first known test of its kind and the first known agreement between computational and experimental work performed in the large scale and rotating turbine research facility AFTRF at the Pennsylvania State University.