Laminar-turbulent breakdown in a swept-wing boundary layer is typically caused by secondary instabilities of steady crossflow vortices (CFVs). So far, boundary-layer suction for laminar flow control in three-dimensional boundary layers has been applied to reduce the crossflow and thus the growth of the primary vortices only. We investigate the influence of strong, localized suction (pinpoint su...

Effects of hydrophobic surface on skin-friction drag are investigated through direct numerical simulations of a turbulent channel flow. Hydrophobic surface is represented by a slip-boundary condition on the surface. When a slip-boundary condition is used in the streamwise direction, the skin-friction drag decreases and turbulence intensities and turbulence structures, near-wall streamwise vorti...

Results of recent experimental measurements of the effect of passive boundary layer flow control method using Large-Eddy Break-Up devices on aero-optical distortions caused by turbulent subsonic boundary layers at a range of trans-sonic speeds are presented. Measurements were performed using a Malley probe to collect instantaneous onedimensional wavefronts with high resolution. Detailed statist...

Entrainment is the process whereby miscible fluid is exchanged across a density interface bounding a region of turbulent flow [17]. It is of central importance in governing the dynamics of the atmospheric boundary layer (ABL) top. In the exchange process, relatively quiescent fluid is engulfed by turbulent motions penetrating across the interface and is subsequently mixed into the turbulent reg...

A non-linear influence of the large-scale log-region motions onto the small-scale near-wall cycle is found to exist in the buffer and log-region of turbulent boundary layers. Based on recent observations of Hutchins & Marusic (2007b) in high Reynolds number turbulent boundary layers, a novel procedure is developed to evaluate the modulation effect. This is done using tools based on Hilbert tran...

A new dynamical subgrid model for turbulent flow is used to derive the structure of the heat and momentum fluxes, mean wind and temperature profiles, and temperature and velocity variances, as a function of the Richardson number, in the surface layer of the planetary boundary layer. Analytical solutions are obtained for stationary, homogeneous surface layers and are compared with field observat...

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Effective delay of turbulent boundary layer separation could be achieved via closed-loop control. Constructing such a system requires that sensor data be processed, real-time, and fed into the controller to determine the output. Current methods for detection of turbulent boundary layer separation are lacking the capability of localized, fast and reliable identification of the boundary layer sta...

This study investigates linear and nonlinear dynamic LES and unified RANS-LES models obtained by stochastic analysis regarding the simulation of the atmospheric boundary layer. The advantages of dynamic LES methods are their accuracy, the ability to account for anisotropy and backscatter, and their computational stability. The advantage of unified RANS-LES models is their ability to provide res...