Measurements and visualization of 3-D unsteady flow field

The measurements and flow visualization results of an 80° delta-wing and Λ-wing are reported in the paper. They contain measurements of vortex spring frequency and model vibration frequency, phase-averaged flow image and re-constructed 3-D flow visualization from 6 parallel laser sheet image. The measurements show that a new flow mechanism has been obtained, i.e. model vibration at high angle of attack may be induced by unsteady vortex spring. The measured vortex spring frequency and model vibration frequency are 7.75Hz and 7.2Hz under the same test condition, respectively. As a new measurements technology and a new concept, phase-averaged flow image at model large amplitude motion offers an ability more accurate to measure position of the vortex over the model. The vortex position from phase-averaged image is as distinct from the time-averaged vortex position. From the multi-laser-sheet image reconstructed 3-D visualization a global domain vortex roll-up or break-down property would be able to investigate.