Search results for "fluid"
showing 10 items of 5513 documents
Stability of Relativistic Hydrodynamical Planar Jets: Linear and Nonlinear Evolution of Kelvin-Helmholtz Modes
2004
Some aspects about the stability of relativistic flows against Kelvin-Helmholtz (KH) perturbations are studied by means of relativistic, hydrodynamical simulations. In particular, we analyze the transition to the fully nonlinear regime and the long-term evolution of two jet models with different specific internal energies.
Strong-field-ionization suppression by light-field control
2012
In recent attempts to control strong-field phenomena such as molecular dissociation, undesired ionization sometimes seriously limited the outcome. In this work we examine the capability of quantum optimal control theory to suppress the ionization by rational pulse shaping. Using a simple model system and the ground-state occupation as the target functional, we show that optimal control generally leads to a significant suppression of the ionization, although the fluence and the pulse length are kept fixed. In the low-frequency regime the ionization is reduced mainly by avoiding high peaks in the intensity and thus preventing tunneling. In contrast, at high frequencies in the extreme ultravio…
Limitation of the ECRIS performance by kinetic plasma instabilities (invited).
2016
Electron cyclotron resonance ion source (ECRIS) plasmas are prone to kinetic instabilities due to anisotropic electron velocity distribution. The instabilities are associated with strong microwave emission and periodic bursts of energetic electrons escaping the magnetic confinement. The instabilities explain the periodic ms-scale oscillation of the extracted beam current observed with several high performance ECRISs and restrict the parameter space available for the optimization of extracted beam currents of highly charged ions. Experiments with the JYFL 14 GHz ECRIS have demonstrated that due to the instabilities the optimum Bmin-field is less than 0.8BECR, which is the value suggested by …
Powerful neutron generators based on high current ECR ion sources with gyrotron plasma heating
2017
This article has no abstract. peerReviewed
Detuning-induced robustness of a three-state Landau-Zener model against dissipation
2019
A three-state system subjected to a time-dependent Hamiltonian whose bare energies undergo one or more crossings, depending on the relevant parameters, is considered, also taking into account the role of dissipation in the adiabatic following of the Hamiltonian eigenstates. Depending on the fact that the bare energies are equidistant or not, the relevant population transfer turns out to be very sensitive to the environmental interaction or relatively robust. The physical mechanisms on the basis of this behavior are discussed in detail.
On the use of an alternative water state equation in SPH
2007
In this work new equations of state for water are formulated, they improve both the consistency and the accuracy of the Smoothed Particles Hydrodynamics (SPH) method to treat incompressible fluid dynamics. When, both physical and artificial viscous terms are introduced, entropy increases. In liquids, the influence of this entropy variation is negligible, but common SPH formulations treats the water as a weakly compressible gas. Therefore, for violent fluid motions, this increase cannot be neglected anymore and the energy equation has to be introduced. This equation has been time integrated, and connected to alternative water state equations which have been studied heuristically. These equat…
Numerical simulations of turbulent flow in an electromagnetically levitated metallic droplet using k-Ω SST and Reynolds stress models
2020
International audience; Electromagnetic levitation of a metallic droplet in the microgravity conditions is modelled accounting for the droplet shape variation, its displacement and turbulent character of the flow in the system. Three different models are applied for description of turbulent flow in the droplet: k − ω SST model and two models based on Reynolds stresses (RSM), all of them resulted in a qualitatively similar flow inside a droplet. Use of RSM-based models leads to a sharper interface of a droplet in volume-of-fluid calculations compared to the k − ω SST model. Two RSM models predict value of the surface tension close to a theoretical one, yet, both fail in predicting of viscosi…
"Table 1.2" of "Probing the effects of strong electromagnetic fields with charge-dependent directed flow in Pb-Pb collisions at the LHC"
2020
Directed flow negative hadrons 5-40%
"Table 1.1" of "Probing the effects of strong electromagnetic fields with charge-dependent directed flow in Pb-Pb collisions at the LHC"
2020
Directed flow positive hadrons 5-40%
"Table 17" of "Search for a Heavy Neutral Particle Decaying to $e\mu$, $e\tau$, or $\mu\tau$ in $pp$ Collisions at $\sqrt{s}=8$ TeV with the ATLAS De…
2015
Cut flow for signal $\tilde{\nu}_{\tau}$ and Z' at 1TeV mass point.