Search results for "hydrodynamic"
showing 10 items of 530 documents
Solar neutrino problem accounting for self-consistent magnetohydrodynamics solution for solar magnetic fields
2001
The analysis of the resonant spin-flavour (RSF) solutions to the solar neutrino problem in the framework of simplest analytic solutions to the solar magneto-hydrodynamics (MHD) equations is presented. We performed the global fit of the recent solar neutrino data, including event rates as well as day and night recoil electron spectra induced by solar neutrino interactions in SuperKamiokande. We compare quantitatively our simplest MHD-RSF fit with vacuum oscillation (VAC) and MSW--type (SMA, LMA and LOW) solutions to the solar neutrino problem using a common well-calibrated theoretical calculation and fit procedure and find MHD-RSF fit to be somewhat better than those obtained for the favored…
A computational magnetohydrodynamic model of a marine propulsion system
2016
In this article we present an approach to the description of Magnetohydrodynamic Propulsion. Preliminarly, an analytical model which includes an electromagnetic model and a thermal model is presented. Successively, in order to move beyond the analytical model, a 3-D MHD modeling tool and a Runge Kutta method based solver are presented and they are used to investigate an alternative MHD solutions. Some numerical analysis are given.
3D Gray Radiative Properties of Accretion Shocks in Young Stellar Objects
2013
International audience; We address the problem of the contribution of radiation to the structure and dynamics of accretion shocks on Young Stellar Objects. Solving the 3D RTE (radiative transfer equation) under our "gray LTE approach", i.e., using appropriate mean opacities computed in local thermodynamic equilibrium, we post-process the 3D MHD (magne-tohydrodynamic) structure of an accretion stream impacting the stellar chromosphere. We find a radiation flux of ten orders of magnitude larger than the accreting energy rate, which is due to a large overestimation of the radiative cooling. A gray LTE radiative transfer approximation is therefore not consistent with the given MHD structure of …
Synchronized rotation in swarms of magnetotactic bacteria.
2017
Self-organizing behavior has been widely reported in both natural and artificial systems, typically distinguishing between temporal organization (synchronization) and spatial organization (swarming). Swarming has been experimentally observed in systems of magnetotactic bacteria under the action of external magnetic fields. Here we present a model of ensembles of magnetotactic bacteria in which hydrodynamic interactions lead to temporal synchronization in addition to the swarming. After a period of stabilization during which the bacteria form a quasiregular hexagonal lattice structure, the entire swarm begins to rotate in a direction opposite to the direction of the rotation of the magnetic …
Acoustic Wave Properties in Footpoints of Coronal Loops in 3D MHD Simulations
2021
Acoustic waves excited in the photosphere and below might play an integral part in the heating of the solar chromosphere and corona. However, it is yet not fully clear how much of the initially acoustic wave flux reaches the corona and in what form. We investigate the wave propagation, damping, transmission, and conversion in the lower layers of the solar atmosphere using 3D numerical MHD simulations. A model of a gravitationally stratified expanding straight coronal loop, stretching from photosphere to photosphere, is perturbed at one footpoint by an acoustic driver with a period of 370 seconds. For this period acoustic cutoff regions are present below the transition region (TR). About 2% …
Photospheric response to an ellerman bomb-like event—an analogy of Sunrise/IMaX observations and MHD simulations
2017
S. Danilovic et. al.
Geometry Diagnostics of a Stellar Flare from Fluorescent X-Rays
2008
We present evidence of Fe fluorescent emission in the Chandra HETGS spectrum of the single G-type giant HR 9024 during a large flare. In analogy to solar X-ray observations, we interpret the observed Fe K$\alpha$ line as being produced by illumination of the photosphere by ionizing coronal X-rays, in which case, for a given Fe photospheric abundance, its intensity depends on the height of the X-ray source. The HETGS observations, together with 3D Monte Carlo calculations to model the fluorescence emission, are used to obtain a direct geometric constraint on the scale height of the flaring coronal plasma. We compute the Fe fluorescent emission induced by the emission of a single flaring coro…
On the convexity of Relativistic Hydrodynamics
2013
The relativistic hydrodynamic system of equations for a perfect fluid obeying a causal equation of state is hyperbolic (Anile 1989 {\it Relativistic Fluids and Magneto-Fluids} (Cambridge: Cambridge University Press)). In this report, we derive the conditions for this system to be convex in terms of the fundamental derivative of the equation of state (Menikoff and Plohr 1989 {\it Rev. Mod. Phys.} {\bf 61} 75). The classical limit is recovered.
Hydrodynamics of nuclear collisions with initial conditions from perturbative QCD
1997
We compute the longitudinal hydrodynamic flow in ultrarelativistic heavy ion collisions at $\sqrt{s}$ = 5500 GeV by using boost non-invariant initial conditions following from perturbative QCD. The transfer of entropy and energy from the central region to larger rapidities caused by boost non-invariance is determined and the associated decrease in the lifetime of the system is estimated.
Controlling stability and transport of magnetic microswimmers by an external field
2019
We investigate the hydrodynamic stability and transport of magnetic microswimmers in an external field using a kinetic theory framework. Combining linear stability analysis and nonlinear 3D continuum simulations, we show that for sufficiently large activity and magnetic field strengths, a homogeneous polar steady state is unstable for both puller and pusher swimmers. This instability is caused by the amplification of anisotropic hydrodynamic interactions due to the external alignment and leads to a partial depolarization and a reduction of the average transport speed of the swimmers in the field direction. Notably, at higher field strengths a reentrant hydrodynamic stability emerges where t…