Current visualization systems give little or no support for user interaction when investigating data and comparing simulation results. If a simulation produces a sequence of images, it is difficult to compare the frames in mind. However, such a comparison is of great importance to the simulation analyst, in order to find out correlation in data, especially in non-consecutive data records. Thus, it is essential to present two or more data records (represented by static images) in a comparable manner. Comparison can be achieved with static techniques, or emphasized with the help of animation tools. There exist several techniques concerning the presentation and merging of data records to be compared. A comparison can operate on complete data records as well as on selected subareas. For the detailed analysis of the simulation, graphical representations like color coding are often too unprecise; an identification of image areas should return the exact values of related data (i.e., take a data probe). In this paper, the authors investigate comparison and identification techniques in the visualization process. A prototype realizing such techniques is presented. The evaluation and verification of several techniques is accomplished with a case study, a 2D simulation in computational fluid dynamics, investigating the time-dependent flow in a rotating channel (e.g., fuel supply for a jet-powered helicopter rotor).