The visualization of computational simulations of complex physical problems using virtual reality technology is demonstrated in this study. A general-purpose computational steering system (POSSE) which can be coupled to any C/C++ simulation code, has been developed and tested with a 3-D parallel Navier-Stokes flow solver (PUMA2). In addition, the visualizations can be displayed using virtual reality facilities (such as CAVEs and RAVEs) to better understand the 3-D nature of the flowfields. The simulations can be run on parallel computers such as Beowulf clusters, while the visualization is performed on other computers, through a client-server approach. A key advantage of our system is its scalability. Visualization primitives are generated on the parallel computer. This is essential for large-scale simulations, since it is often not possible to post-process the entire flowfield on a single computer due to memory and speed constraints. Example applications of time-dependent and three-dimensional computational flow simulations performed at Penn-State are presented to show the usefulness of POSSE and virtual reality systems. The examples include CFD predictions for unsteady simulations of a helicopter rotor, unsteady ship airwake simulations, helicopter tail fan-in-fin flow simulations and simulations of time-accurate flow and noise due to a landing gear.