Search results for "fluid"
showing 10 items of 5513 documents
Simple absorbing layer conditions for shallow wave simulations with Smoothed Particle Hydrodynamics
2013
Abstract We study and implement a simple method, based on the Perfectly Matched Layer approach, to treat non reflecting boundary conditions with the Smoothed Particles Hydrodynamics numerical algorithm. The method is based on the concept of physical damping operating on a fictitious layer added to the computational domain. The method works for both 1D and 2D cases, but here we illustrate it in the case of 1D and 2D time dependent shallow waves propagating in a finite domain.
A density functional for liquid3He
1993
We present a density functional for the description of liquid3He properties at zero temperature in a mean field approximation. Its basic ingredients are a zero-range, particle- and spin-density dependent effective interaction of Skyrme type, and a long-range effective interaction of Lennard-Jones type supplemented with a weighted density approximation similar to the one used in the study of classical fluids, to phenomenologically account for short range correlations. After fixing the value of its parameters, the functional yields a good description of the equation of state and Landau parameters (spin symmetric and spin antisymmetric as well) from saturation to solidification densities. The …
A generalization of the Carnahan–Starling approach with applications to four- and five-dimensional hard spheres
2018
Abstract Development of good equations of state for hard spheres is an important task in the study of real fluids. In a way consistent with other theoretical results, we generalize the famous Carnahan–Starling approach for arbitrary dimensions and apply it to four- and five-dimensional hard spheres. We obtain simple and integer representations for virial coefficients of lower orders and accurate equations of state. Since theoretically and practically validated, these results improve understanding of hard sphere fluids.
The screened cluster equation of state for hydrogen-helium mixtures: Atomic, molecular, and ionic contributions from first principles
2018
International audience
On numerical relativistic hydrodynamics and barotropic equations of state
2012
The characteristic formulation of the relativistic hydrodynamic equations (Donat et al 1998 J. Comput. Phys. 146 58), which has been implemented in many relativistic hydro-codes that make use of Godunov-type methods, has to be slightly modified in the case of evolving barotropic flows. For a barotropic equation of state, a removable singularity appears in one of the eigenvectors. The singularity can be avoided by means of a simple renormalization which makes the system of eigenvectors well defined and complete. An alternative strategy for the particular case of barotropic flows is discussed.
On the Measurements of Numerical Viscosity and Resistivity in Eulerian MHD Codes
2016
We propose a simple ansatz for estimating the value of the numerical resistivity and the numerical viscosity of any Eulerian MHD code. We test this ansatz with the help of simulations of the propagation of (magneto)sonic waves, Alfven waves, and the tearing mode instability using the MHD code Aenus. By comparing the simu- lation results with analytical solutions of the resistive-viscous MHD equations and an empirical ansatz for the growth rate of tearing modes we measure the numerical viscosity and resistivity of Aenus. The comparison shows that the fast-magnetosonic speed and wavelength are the characteristic velocity and length, respectively, of the aforementioned (relatively simple) syst…
Analysis of the static and dynamic behaviour of a magnetic liquid seal
1985
A rotating shaft seal, using ferrofluid between biconical truncated magnetic poles, is analysed both in static and dynamic conditions. After solving Laplace's equation and allowing an approximate expression for the magnetic potential, the magnetic forces acting on the working fluid are obtained. It is thus possible to determine the baric field existing in static conditions and the highest tolerable pressure jump. In the case of dynamic working the flow is schematized by two interior regions, where the azimuthal velocity prevails, and four boundary layers on the walls, where meridional transport of fluid takes place. Assuming laminar motion, by means of a perturbation procedure it is possibl…
SANS polarization analysis at V4 SANS instrument of HMI Berlin
2008
The V4 instrument has recently been upgraded with a 3He spin filter cell, placed directly in the homogeneous field B of the sample magnet, to enhance the SANSPOL option for polarization analysis. The prototype setup was still affected by: (a) a quick relaxation of the 3He nuclear polarization in the cell with a time constant of only ?130 min which significantly changes the spin filter transmissions T+ and T? for neutrons polarized parallel I+ and anti-parallel I? to B, and (b) the absence of a flipping aid behind the sample. The usual polarization analysis procedure, expecting virtually time-independent transmissions and a second flipping device, is therefore not applicable. We present an a…
Influence of electromagnetic boundary conditions onto the onset of dynamo action in laboratory experiments
2009
We study the onset of dynamo action of the Riga and Karlsruhe experiments with the addition of an external wall, the electro-magnetic properties of which being different from those of the fluid in motion. We consider a wall of different thickness, conductivity and permeability. We also consider the case of a ferro-fluid in motion.
Modeling vibrating panels excited by a non-homogeneous turbulent boundary layer
2021
Abstract Predicting the vibration response of an elastic structure excited by a turbulent flow is of interest for the civil and military transportation sector. The models proposed in the literature are generally based on the assumption that the turbulent boundary layer (noted TBL in the following) exciting the structure is spatially homogeneous. However, this assumption is not always fulfilled in practice, in particular when the excited area is close to the starting point of the TBL or with curved structures. To overcome this issue, this work proposes to extend two approaches generally used for dealing with homogeneous TBL, namely the spatial and the wavenumber approaches. The extension of …