We have performed direct numerical simulation of fully developed turbulent flow in a straight duct with square cross-section. The main objective of the present study is to determine the minimal requirements for maintaining turbulence in duct flows [1]. A detailed analysis of this limit regime allows to elucidate the dominant mechanisms governing the marginally turbulent state, where the self-su...

Locally parallel dense patterns—sometimes called texture flows—define a perceptually coherent structure of particular significance to perceptual organization. We argue that with applications ranging from image segmentation and edge classification to shading analysis and shape interpretation, texture flows deserve attention equal to edge segment grouping and curve completion. This paper develops...

Stochastic Coherent Adaptive Large Eddy Simulation (SCALES) methodology, originally proposed by Goldstein and Vasilyev [1], is an extension of the Large Eddy Simulation (LES) approach that uses a wavelet filter-based dynamic grid adaptation strategy to solve for the most energetic coherent structures in a turbulent flow field, while modeling the effect of the less energetic eddies. Despite some...

We develop an efficient Eulerian numerical approach to extract invariant sets in a continuous dynamical system in the extended phase space (the x− t space). We extend the idea of ergodic partition and propose a concept called coherent ergodic partition for visualizing ergodic components in a continuous flow. Numerically, we first apply the level set method [33] and extend the backward phase flo...

Doppler devices can provide clinically useful information about blood flow. This paper describes how a pulse-Doppler instrument has been linked to a B-scan machine so that flow patterns in any ultrasonically accessible vessel can be monitored from the skin surface. The same transducer is used for both modes of investigation to enable accurate and reliable positioning of the sample-volume. After...

Controlled islanding is the last countermeasure for a bulk power system when it suffers from severe cascading contingencies. The objective of controlled islanding is to maintain the stability of each island and to keep the total loss of loads of the whole system to a minimum. This paper presents a novel integrated wide-area measurement systems (WAMS)-based adaptive controlled islanding strategy...

The KelvinHelmholtz (KH) instability is a fundamental wave instability that is frequently observed in all kinds of shear layer (jets, wakes, atmospheric air currents etc). The study of KH-instability, coherent flow structures has a major impact in understanding the fundamentals of fluid dynamics. Therefore there is a need for methods that can identify and analyse these structures. In this Final...

We present experimental results on turbulence generated in thin fluid layers in the presence of a large-scale coherent flow, or a spectral condensate. It is shown that the condensate modifies the third-order velocity moment in a much wider interval of scales than the second one. The modification may include the change of sign of the third moment in the inverse cascade. This observation may help...

We present feature-extraction techniques for numerical and experimental data of complex fluid flows. Focus is placed on efficient analysis and visualization of coherent structures of snapshots, temporal evolution and parameter-dependency of coherent structures. One key enabler are Galilean invariant flow quantities based on pressure, acceleration, vorticity and velocity Jacobians. Other importa...