The stability of modulated atmospheric flows is analyzed. The equations govern. ing the disturbance motion are solved by Galerkin expansions with time-dependent coefficients. Asymptotic stability bounds are then established by constructing Liapuno"\ functions for the resulting differential systems.

The characteristics of steady granular flow in quasi-two-dimensional rotating tumblers have been thoroughly investigated and are fairly well understood. However, unsteady time-varying flow has not been studied in detail. The linear response of granular flow in quasi-two-dimensional rotating tumblers is presented for periodic forcing protocols via sinusoidal variation in the rotational speed of ...

Very complex flow structures occur during separation that can appear in a wide variety of applications involving flow over a bluff body. This study examines the ability to detect the dynamic interactions of vortical structures generated from a Helmholtz instability caused by separation over bluff bodies at large Reynolds number of approximately 104 based on a cross stream characteristic length ...

In this paper we present GPU-based techniques for the interactive visualization of large unsteady 3D flow fields on uniform grids. We propose a novel dual-core approach to asynchronously stream such fields from the CPU, thus enabling the efficient exploration of large time-resolved sequences. This approach decouples visualization from data handling, resulting in interactive frame rates. Built u...

The paper is devoted to discrete optimization of the viscous heatconducting fluid flows. In the problem under consideration we want to create a flow with desired properties using optimal heating or cooling on some boundary sections. Optimal control approach reduces this problem to the constrained minimization. In this case the cost functional describes the objectives, mathematical model is the ...

where T is the stress tensor, p the hydrostatic pressure, S the extra-stress tensor, A the first RivlinEricksen tensor and μ the dynamic viscosity. Many common fluids show this “Newtonian” behavior and in fact the whole discipline of classical fluid mechanics is based upon this equation. However, the constitutive equation (1) does not show any of the normal stress effects or relaxation phenomen...

This paper deals with the new method to compute very low mach number flow and sound propagation at same time. The new method is shown effective both steady and unsteady flows.

The objective of this paper is to understand transport behavior in uncertain time-varying flow fields by redefining the finite-time Lyapunov exponent (FTLE) and Lagrangian coherent structure (LCS) as stochastic counterparts of their traditional deterministic definitions. Three new concepts are introduced: the distribution of the FTLE (D-FTLE), the FTLE of distributions (FTLE-D), and uncertain L...

The visualization of unsteady ows is an attractive eld of research and texture-based techniques seem to provide satisfactory results. In this paper we propose a texture-based method which follows streaklines in order to produce an eeective visualization of time-dependent phenomena. The local vorticity of the eld allows to trace a number of streaklines according to the ow characteristics; in thi...

We present detailed analysis of a lattice Boltzmann approach to model time-dependent Newtonian flows. The aim of this study is to find optimized simulation parameters for a desired accuracy with minimal computational time. Simulation parameters for fixed Reynolds and Womersley numbers are studied. We investigate influences from the Mach number and different boundary conditions on the accuracy a...