An experimental investigation is made of smooth wall turbulent boundary layers under a family of continually varying streamwise pressure gradient distributions. In general, the effects of these pressure gradient cases on the boundary layer are found to be nonlocal and dependent on upstream history effects. However, the friction Reynolds number grows independent of applied pressure gradient and appears to be dependent only on the origin of the turbulent boundary layer. Special attention is paid to the statistics of the fluctuating pressure on the immersed surface, and it is found that there is a spectral-region-dependent relationship between pressure gradient and the fluctuating wall pressure, indicating the lack of a universal overlap region and providing insight into the impact of pressure gradient history on turbulence evolution. The classical viscous inner scaling of the pressure spectra appears universal as does a proposed mixed variable low-frequency scaling. The impact of the pressure gradients on the pressure space-time correlations and convection velocities is more locally dependent. The implications of these observations on our understanding of nonequilibrium flows are explored, and it is postulated that such flows may be describable as a three-dimensional space governing the mean growth, pressure gradient effect, and nonequilibrium effect, respectively.
Fluctuating Pressure Beneath Smooth Wall Boundary Layers in Nonequilibrium Pressure Gradients
AIAA Journal ; 60 , 8 ; 4725-4743
2022-05-16
19 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch