![]() ![]() Proceeding of FLUCOME '03 : seventh triennial international symposium on fluid control, measurement and visualization (literal).La Gala (2003) AIRCRAFT WAKE VORTEX DETECTION IN LARGE TOWING TANK in TRIENNIAL INTERNATIONAL SYMPOSIUM ON FLUID CONTROL, MEASUREMENT AND VISUALIZATION, Sorrento, Settembre 2003 (literal) The quadrant analysis contribution to the energy production revealed that ejections still dominated the balance and that the production was spatially modulated in the wind direction with a couple of cells and with a minimum in the area of the free surface wave height reduction.F. Turbulence energy production peaked at z/d = 0.2 and had a distribution similar to that observed for a self-preserving boundary layer with a strong adverse gradient pressure. At small fetches, the large-amplitude negative streamwise perturbations were preferentially lifted. The quadrant analyses revealed that ejection and sweep events were dominant and more concentrated. Here, the presence/absence of water damps out the turbulence. The intermittency factor in the boundary layer over water waves was similar to that in a boundary layer over a rigid plane wall, with several differences near the interface. Wave induced Reynolds stresses became negligible for z[5 Hrms. The contribution of the wave-induced Reynolds stress was detected through filtering the spectrum of velocity fluctuations. Here, the structure of the boundary layer on the air side of the water– air interface was analysed and compared with the boundary layer over a smooth plane rigid wall. This is the second paper in a group of three that reports the systematic measurements of wind-generated water waves in a wind tunnel experiment. Wall-normal turbulence measurements remain compromised by limited particle frequency response. ![]() A final assessment of the data reveals that Morkovin scaling col- lapses the streamwise turbulence profiles with DNS at the same Mach number. The e↵ect of over-large tripping devices was also found to increase the wake strength of the mean velocity profile as well as freestream turbulence. Significantly, an examination of parti- cle dynamics, subject to fluid inertia,compressibility and non-continuum e↵ects, revealed that particle frequency responses to turbulence can be up to an order of magnitude smaller than estimates made using a standard shock response test. Limited resolution or dynamic range e↵ects were minimized and the e↵ects of high shear on cross-correlation routines were examined. To study the characteristics of a hypersonic turbulent boundary layer at Mach 8, sig- nificant improvements were required to the implementation and error characterization of PIV. Further investigations examined turbulent boundary layer structure and changes to the motions that contribute to turbulent production. The critical bulk stratification was found to be sensitive to surface roughness and potentially Reynolds number, and not constant as previously thought. Changes in profile shape were shown to correlate with the local stratification profile, and as a result, the collapse of near-wall turbulence is not intrinsic to the strongly stable regime. The turbulent stresses were found to scale with the wall shear stress in the weakly stable regime prior relaminarization at a critical stratification. To examine the characteristics of these two regimes, PIV measurements were ob- tained in conjunction with the mean temperature profile in a low Reynolds number facility over smooth and rough surfaces. Previous experimental studies examining the e↵ects of stability on turbulent boundary layers identified two regimes, weak and strong stability, separated by a critical bulk stratifi- cation with a collapse of near-wall turbulence thought to be intrinsic to the strongly stable regime. Two distinct cases were examined: the thermally stable atmospheric surface layer characteristic of nocturnal or po- lar conditions, and the hypersonic bounder layer characteristic of high speed aircraft and reentering spacecraft. His dissertation examines the e↵ects of density gradients on turbulent boundary layer statistics and structure using Particle Image Velocimetry (PIV).
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