Hasil untuk "physics.flu-dyn"

Julien Mathiaud, Luc Mieussens, Marcel Pfeiffer

We propose a new ES-BGK model for diatomic gases which allows for translational-rotational and translational-vibrational energy exchanges, as given by Landau-Teller and Jeans relaxation equations. This model is consistent with the general definition of the vibrational and rotational collision numbers that are also commonly used in DSMC solvers. It is proved to satisfy the H-theorem and to give the correct transport coefficients, up to the volume viscosity.

Abhik Kumar Sanyal, D. Ray

While studying the viscoelastic flow past an infinite plate with suction and constant heat flux between fluid and plate, Raptis and Tziyanidis gave the solution of a pair of equations for velocity and temperature as functions of distance. They then gave some approximate solutions. This letter shows that the approximations are not justified and presents an exact analytical study.

Lukas Harsch, Stefan Riedelbauch

We propose a model to directly predict the steady-state flow field for a given geometry setup. The setup is an Eulerian representation of the fluid flow as a meshed domain. We introduce a graph network architecture to process the mesh-space simulation as a graph. The benefit of our model is a strong understanding of the global physical system, while being able to explore the local structure. This is essential to perform direct prediction and is thus superior to other existing methods.

A. Bershadskii

Results of direct numerical simulations and laboratory experiments have been used in order to show that the buoyancy driven bubbly flows at high gas volume fraction are mixed by deterministic chaos with typical exponential spectrum of the liquid kinetic energy, whereas at moderate and small gas volume fraction it is a distributed chaos (turbulence or pseudo-turbulence) dominated by the third and second moments of helicity distribution with the stretched exponential spectra of the kinetic energy. Interaction of the bubbles with isotropic (behind an active grid) and near-wall turbulent flows has been also discussed from this point of view with an application to the pressurized water nuclear reactors.

Alexander V. Proskurin, Anatoly M. Sagalakov

In the article the authors present a numerical method for modelling a laminar-turbulent transition in magnetohydrodynamic flows. The equations in the small magnetic Reynolds numbers approach is considered. Speed, pressure and electrical potential are decomposed to the sum of the state values and the finite amplitude perturbations. A solver based on the Nectar++ framework is described. The authors suggest to use of small-length local disturbances as a transition trigger. They can be imposed by blowing or electrical enforcing. The stability of the Hartmann flow and the flow in the bend are considered as examples.

A. Bershadskii

Multiple chaotic and turbulent regimes in Rayleigh-Bénard convection have been studied and classified from the onset of deterministic chaos to the fully developed turbulence using the distributed chaos approach supported by results of laboratory experiments and numerical simulations. It is shown that the regimes can replace each other depending on value of the Rayleigh number and location in the convection cell (in the bulk of the flow or in the boundary layers). The inertial-buoyancy and helicity based invariants play crucial role in the formation of the regimes. Transition from the classical to ultimate state has been also discussed in this context.

Francisco Mandujano Carlos Málaga

The problem of the flow trough a porous media is formulated in terms of a pressure equation, based on arguments of volume conservation which state the mechanical equilibrium between the solid and the fluid phases. In the resulting governing equations, the conservation of mass is replaced by a transport-diffusion equation for the pressure field. When the deformation of the solid matrix is negligible, the pressure equation can be approximated by a non-linear diffusion equation. The behavior of the system of equations is tested under an oscillatory pressure gradient.

Alexander V. Proskurin, Anatoly M. Sagalakov

A two-dimensional flow in a 90 degree bent channel is considered. A magnetic field is uniform and parallel to inlet branch of the channel. A spectral/hp element method was used for liquid motion calculations. Three types of steady flows were detected. It was found that magnetic forces can suppress a pressure gradient and throw out liquid from the inlet, a relatively large reverse flow appears.

Piotr Rozmej, Anna Karczewska

We derived consistently, according to the second order perturbation approach, the extended KdV equation for an uneven bottom for the case of $α=O(β)$ and $δ=O(β^2)$. This equation can be obtained only when the bottom is given by a piecewise linear function. For the case of $α=O(β)$ and $δ=O(β)$, a unidirectional wave equation is derived in the first order approach with the same limitation for the bottom profile.

Mehdi Mirzakhanloo, Mohammad-Reza Alam

Here we show that micro-swimmers can form a concealed swarm through synergistic cooperation in suppressing one another's disturbing flows. We then demonstrate how such a concealed swarm can actively gather around a favorite spot, point toward a target, or track a desired trajectory in space, while minimally disturbing the ambient fluid. Our findings provide a clear road map to control and lead flocks of swimming micro-robots in stealth versus fast modes, tuned through their active collaboration in minimally disturbing the host medium.

Leonid Korelstein

Existence, Uniqueness and monotonic behavior of the solution of classical flow distribution problem for hydraulic networks with pressure-dependent closure relations was proved. Structure and properties of inverse Maxwell matrix of the problem were investigated

Rachel I. Anderson, Melissa Morales, L. Spear et al.

Nai-Jiang Liu, S. Schnell, M. Wessendorf et al.

E. Okal

M. Sabin, N. Dodgson

A. Tilgner

Numerical simulations of dynamos in rotating Rayleigh-Bénard convection in plane layers are presented. Two different types of dynamos exist which obey different scaling laws for the amplitude of the magnetic field. The transition between the two occurs within a hydrodynamically uniform regime which can be classified as rapidly rotating convection.

S. Murarka, D. Fraser

Matthieu Dreyer, Mohamed Farhat

Video of vortex shedding in the wake of a Naca0009 hydrofoil made of polyoxymethylene type C (POM C). This video was submitted as part of the Gallery of Fluid Motion 2011 which is showcase of fluid dynamics videos.

I. Lilliehöök, H. Tvedten

Y. Nakayama, Jessica M. Shivas, D. Poole et al.