Search results for "hydrodynamic"
showing 10 items of 530 documents
Inner Edge Drag by an Asynchronous Primary and Accretion Disc Structure In Close Binaries
1996
In this work a 3-D ‘Smoothed Particle Hydrodynamics’ ([1]; [4]; [5]) accretion disc is simulated where particles at its inner edge are dragged by a fast spinning compact central star, as in the case of the intermediate polars. The angular velocity of the central star is twice the orbital angular velocity w 0. This drag can be attributed mainly to viscous interaction in the dense compact star atmosphere, although magnetic coupling may also play a role.
First Experiences on an Accurate SPH Method on GPUs
2017
It is well known that the standard formulation of the Smoothed Particle Hydrodynamics is usually poor when scattered data distribution is considered or when the approximation near the boundary occurs. Moreover, the method is computational demanding when a high number of data sites and evaluation points are employed. In this paper an enhanced version of the method is proposed improving the accuracy and the efficiency by using a HPC environment. Our implementation exploits the processing power of GPUs for the basic computational kernel resolution. The performance gain demonstrates the method to be accurate and suitable to deal with large sets of data.
The mathematical modeling of the single and ensemble dynamics of magnetic filaments
2016
Biomimētisku sistēmu izmantošana mikrodzinēju un šķidrumu maisītāju izveidei ir aktuāls izpētes objekts mīksto materiālu nozarē. Šiem mērķiem iespējams izmantot magnētiskas stīgas, ko ir viegli kontrolēt mainot ārēja magnētiskā lauka parametrus. Šajā darbā ir izveidots magnētisku stīgu matemātisks modelis, kas ietver gan vērp es, gan hidrodinamisko mijiedarbību ietekmi dažādos tuvinājumos un izveidota praktiska implementācija divu programmatūras bibliotēku formā. Ar izveidotā modeļa palīdzību iegūti rezultāti, kas raksturo individuālu stīgu un stīgu ansambļu dinamika plašā kustību kontrolējošo parametru diapazonā un iegūti jauni rezultāti, kas raksturo feromagnētisku un superparamagnētisku …
3D MHD MODELING of TWISTED CORONAL LOOPS
2016
We perform MHD modeling of a single bright coronal loop to include the interaction with a non-uniform magnetic field. The field is stressed by random footpoint rotation in the central region and its energy is dissipated into heating by growing currents through anomalous magnetic diffusivity that switches on in the corona above a current density threshold. We model an entire single magnetic flux tube, in the solar atmosphere extending from the high-beta chromosphere to the low-beta corona through the steep transition region. The magnetic field expands from the chromosphere to the corona. The maximum resolution is ~30 km. We obtain an overall evolution typical of loop models and realistic loo…
Magnetohydrodynamic study on the effect of the gravity stratification on flux rope ejections
2013
Context. Coronal mass ejections (CMEs) are the most violent phenomenon found on the Sun. One model that explains their occurrence is the flux rope ejection model. A magnetic flux rope is ejected from the solar corona and reaches the interplanetary space where it interacts with the pre-existing magnetic fields and plasma. Both gravity and the stratification of the corona affect the early evolution of the flux rope. Aims. Our aim is to study the role of gravitational stratification on the propagation of CMEs. In particular, we assess how it influences the speed and shape of CMEs and under what conditions the flux rope ejection becomes a CME or when it is quenched. Methods. We ran a set of MHD…
Tracing the ICME plasma with a MHD simulation
2021
The determination of the chemical composition of interplanetary coronal mass ejection (ICME) plasma is an open issue. More specifically, it is not yet fully understood how remote sensing observations of the solar corona plasma during solar disturbances evolve into plasma properties measured in situ away from the Sun. The ambient conditions of the background interplanetary plasma are important for space weather because they influence the evolutions, arrival times, and geo-effectiveness of the disturbances. The Reverse In situ and MHD APproach (RIMAP) is a technique to reconstruct the heliosphere on the ecliptic plane (including the magnetic Parker spiral) directly from in situ measurements a…
A fast multi-dimensional magnetohydrodynamic formulation of the transition region adaptive conduction (TRAC) method
2021
We have demonstrated that the Transition Region Adaptive Conduction (TRAC) method permits fast and accurate numerical solutions of the field-aligned hydrodynamic equations, successfully removing the influence of numerical resolution on the coronal density response to impulsive heating. This is achieved by adjusting the parallel thermal conductivity, radiative loss, and heating rates to broaden the transition region (TR), below a global cutoff temperature, so that the steep gradients are spatially resolved even when using coarse numerical grids. Implementing the original 1D formulation of TRAC in multi-dimensional magnetohydrodynamic (MHD) models would require tracing a large number of magne…
Chromospheric evaporation and phase mixing of Alfvén waves in coronal loops
2020
Phase mixing of Alfv\'en waves has been studied extensively as a possible coronal heating mechanism but without the full thermodynamic consequences considered self-consistently. It has been argued that in some cases, the thermodynamic feedback of the heating could substantially affect the transverse density gradient and even inhibit the phase mixing process. In this paper, we use MHD simulations with the appropriate thermodynamical terms included to quantify the evaporation following heating by phase mixing of Alfv\'en waves in a coronal loop and the effect of this evaporation on the transverse density profile. The numerical simulations were performed using the Lare2D code. We set up a 2D l…
Hydrodynamics with spin in bacterial suspensions
2016
We describe a new kind of self-propelling motion of bacteria based on the cooperative action of rotating flagella on the surface of bacteria. Describing the ensemble of rotating flagella in the framework of the hydrodynamics with spin the reciprocal theorem of Stokesian hydrodynamics is generalized accordingly. The velocity of the self-propulsion is expressed in terms of the characteristics of the vector field of flagella orientation and it is shown that unusually high velocities of \textit{Thiovulum majus} bacteria may be explained by the cooperative action of the rotating flagella. The expressions obtained enable us to estimate the torque created by the rotary motors of the bacterium and …
A mesoscopic mechanical model of the surface tension and some simulation results
2019
Abstract Drops of mercury do not spread on a surface. A metal paper clip can float on water. These phenomena are macroscopic manifestations of molecular interactions and can be explained in terms of surface tension. In this study, we discuss a simple mesoscopic mechanical model of the surface tension and the results of numerical fluid dynamics simulations implemented on the basis of it. We study the droplet formation without and with gravity when it can drop from a narrow hole like a trickling tap and finally the behaviour of free surface liquid in a vessel. Teachers and students can be able to study the surface tension by using the computer simulation as a “tool” for analysing and discussi…