The results of the computation of entropy generation rates through the dissipation of ordered regions within selected helium boundary layer flows are presented. Entropy generation rates in helium boundary layer flows for five cases of increasing temperature and pressure are considered. The basic format of a turbulent spot is used as the flow model. Statistical processing of the time-dependent s...

After a brief summary of experimental results focussed on plane Couette flow and contrasting the low-Reynolds numbers transition between laminar flow and the turbulent spot regime, with its high-Reynolds counterpart between homogeneous turbulence and turbulent stripes, we introduce a hierarchy of models from conceptual models designed to answer the most basic questions to semi-realistic models ...

1 The propagation of a laser beam through turbulent media is modeled as a fractional Brownian motion (fBm). Time series corresponding to the center position of the laser spot (coordinates x and y) after traveling across air in turbulent motion, with different strength, are analyzed by the wavelet theory. Two quantifiers are calculated, the Hurst exponent, H, and the mean Normalized Total Wavele...

A study with experimental and numerical components is conducted to establish the effect of a two-dimensional surface cavity on structure growth rate turbulent spot. The spot artificially created in laminar boundary layer developing under zero streamwise pressure gradient. Interactions its wake Kelvin–Helmholtz rollers shear are shown result significant increases lateral rates. underlying physic...

We demonstrate that the space-time statistics of the birth of turbulent spots in boundary layers can be reconstructed qualitatively from the average behavior of macroscopic measures in the transition zone. The conclusion in [1] that there exists a connection between the patterns in laminar instability and the birth of turbulent spots is strengthened. We examine why the relationship between inst...

We present multi-color photometry and time resolved spectroscopy of OU Vir. The analysis of the quiescent light curve shows that OU Vir is characterized by i) strong cycle-to-cycle brightness variations, and ii) hot spot modulated light curve with grazing eclipse of the impact region. Colors are derived both in-and out-of eclipse. The time-resolved spectroscopy allows us to produce the radial v...

Numerical simulations of a model of plane Couette flow focusing on its in-plane spatio-temporal properties are used to study the dynamics of turbulent spots. While the core of a spot is filled with small scale velocity fluctuations, a large scale flow extending far away and occupying the full gap between the driving plates is revealed upon filtering out small scales. It is characterized by stre...