The development of a measurement system to visualize, classify(based on topological features) and quantify complex flows in largescale wind tunnel experiments is described. A new approach is soughtwhere the topological features of the flow, e.g. stream lines,separation and reattachment regions, stagnation points and vortex linesare extracted directly and preferably visualized in realtime in avirtual wind tunnel environment. The system is based on a threedimensional particle tracking method (3D-PTV) using a stereo arrangementof 2 CCD cameras. A frame rate of 120 frames/s allows measurements athigh flow velocities. For the 3D-PTV method an approach is taken wherethe tracer particles are recorded such that consecutive frames formcontinuous path lines. The 3-dimensional positions and shapes of theparticle path lines are reconstructed by means of the epipolarconstraint and the stereo camera model. The particle path segments whichcontain both velocity and topological information are then analysed toextract the relevant information. Neutrally buoyant helium bubbles areused as tracer particles. Matching the density of the ambient air, thebubbles are ideal flow tracers in this respect
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