Visualization of CFD data for turbomachinery design poses some special requirements which are often not addressed by standard flow visualization systems. We discuss the issues involved with this particular application and its requirements with respect to flow visualization. Aiming at a feature-based visualization for this task, we will examine various existing techniques to locate vortices. The specific flow conditions for turbomachines demonstrate limitations of current methods. Visualization of turbomachinery flow thus raises some challenges and research topics, particularly regarding feature extraction.