Nonlinear coupling among wave modes and vortical modes is investigated with the following question in mind: Can we distinguish the wave-vortical interactions largely responsible for formation versus evolution of coherent, balanced structures? The two main case studies use initial conditions that project only onto the vortical-mode flow component of the rotating Boussinesq equations: (i) an init...

A large-eddy simulation (LES) solver which combines an immersed-boundary technique with a curvilinear structured grid has been developed to study the temporal and spatial dynamics of a rotor tip-clearance flow, with the objective of determining the underlying mechanisms for low pressure fluctuations downstream of the rotor near the endwall. Salient feature of the numerical methodology, includin...

The detection and tracking of coherent vortical structures in a turbulent compressible boundary layer is considered. Several vortex identification methods are evaluated. It is found that for this flow, the discriminant of the characteristic polynomial of the velocity gradient tensor is the most useful. It tends to highlight vortical structures that are located farther from the wall, and the fea...

Swimming microalgae show various taxes, such as phototaxis and gravitaxis, which sometimes result in the formation of a cell-rich layer or a patch in a suspension. Despite intensive studies on the effects of shear flow and turbulence on the inhomogeneous distribution of microalgae, the effect of a bubble plume has remained unclear. In this study, we used Chlamydomonas as model microalgae, and i...

A boundary layer wind tunnel facility has been adopted in order to conduct experimental measurements of the flow field around a model of the Panorama Giustinelli Building, Trieste (Italy). Information on the main flow structures has been obtained by means of flow visualization techniques and has been compared to the numerical predictions of the vortical structures spread on top of the roof, in ...

Vortical flows are one of the most fascinating topics in fluid mechanics. A particular difficulty of modelling such flows at high Reynolds (Re) numbers is the diversity of space and time scales that emerge as the flow develops. For compressible flows, in particular, there are additional degrees of freedom associated with the shocks and acoustic waves. The latter can have very different characte...

by Jacob Allen Cress The relationship between optical aberrations and coherent structures in the turbulent boundary layer is investigated in a series of experiments. A statistical model is derived using the “extended” Strong Reynolds Analogy that allows the total temperature to vary and also presumes pressure fluctuations in the boundary layer are negligible compared to temperature fluctuations...

It has long been customary to assume that vortical structures in turbulent flows are synonymous with regions of rotational motion. Mathematical implementations of this idea using numerical and experimental velocity data from turbulent boundary layers reveal the presence of hairpin vortices, both singly and in groups called packets. However, vorticity may be present that does not directly cause ...

The current study presents the results of the aerodynamic noise prediction of the flow field around a NACA 0012 airfoil at a chord-based Reynolds number of 100,000 and at 8.4 degree angle of attack. An incompressible Large Eddy Simulation (LES) turbulence model is applied to obtain the instantaneous turbulent flow field. The noise prediction is performed by the Ffowcs Williams and Hawkings (FW-...