Search results for " Simulation"
showing 10 items of 4034 documents
Coupled fluid-flow and magnetic-field simulation of the Riga dynamo experiment
2006
Magnetic fields of planets, stars, and galaxies result from self-excitation in moving electroconducting fluids, also known as the dynamo effect. This phenomenon was recently experimentally confirmed in the Riga dynamo experiment [ A. Gailitis et al., Phys. Rev. Lett. 84, 4365 (2000) ; A. Gailitis et al., Physics of Plasmas 11, 2838 (2004) ], consisting of a helical motion of sodium in a long pipe followed by a straight backflow in a surrounding annular passage, which provided adequate conditions for magnetic-field self-excitation. In this paper, a first attempt to simulate computationally the Riga experiment is reported. The velocity and turbulence fields are modeled by a finite-volume Navi…
The Numerical Simulation of Relativistic Fluid Flow with Strong Shocks
2001
In this review we present and analyze the performance of a Go-dunov type method applied to relativistic fluid flow. Our model equations are the corresponding Euler equations for special relativistic hydrodynamics. By choosing an appropriate vector of unknowns, the equations of special relativistic fluid dynamics (RFD) can be written as a hyperbolic system of conservation laws. We give a complete description of the spectral decomposition of the Jacobian matrices associated to the fluxes in each spatial direction, (see (Donat et al., 1998), for details), which is the essential ingredient of the Godunov-type numerical method we propose in this paper. We also review a numerical flux formula tha…
A Model for Homogenization of Solid Alloying Admixtures in an Induction Crucible Furnace
2014
The paper presents a methodology for identification of homogenization time of alloying inclusions in an induction crucible furnace. The methodology is based on the Large Eddy Simulation (LES) Euler-Lagrange calculation of inclusions and a regression model for size of the inclusions and their density. The presented regression model avoids the repeated LES calculations and, therefore, is suitable for an optimization task.
Numerical simulation and analysis of heat and mass transfer processes in metallurgical induction applications
2009
Comprehensive knowledge of the heat and mass transfer processes in the melt of induction applications is required to realize efficient metallurgical processes. Experimental and numerical studies of the melt flow in induction furnaces show that the flow pattern, which comprise several vortexes of the mean flow, and the temperature distribution in the melt are significantly influenced by low-frequency large scale flow oscillations. Two- and three-dimensional hydrodynamic calculations of the melt flow, using two-equation turbulence models based on Reynolds Averaged Navier-Stokes approach, do not predict the large scale periodic flow instabilities obtained from the experimental data. That's why…
Field and numerical study of river confluence flow structures
2010
River hydrodynamics Turbulent open channel flow and transport phenomena
Effect of a Steady Magnetic Field and Imposed Rotation of Vessel on Heat and Mass Transfer in Swirling Recirculating Flows
1999
A simplified theoretical model for the solidification interface shape prediction is introduced and tested. We linearised a coupled hydrodynamic-solidification problem about the state with a flat interface. In such a way we split the problem into a hydrodynamic part with a flat solid-liquid front and a solidification part with a calculated heat flux from the liquid phase. The method allows obvious conclusions on optimum heat conditions near the solidification interface providing its flatness and maximum pulling velocity at the same time. Comparison to the results by FLUENT package showed that the method provides a reasonable accuracy even for a noticeably deformed interface shape. Another pa…
Linear and non-linear stability of a thermally stratified magnetically driven rotating flow in a cylinder
2010
The stability of a thermally stratified liquid metal flow is considered numerically. The flow is driven by the rotating magnetic field in a cylinder heated from above and cooled from below. The stable thermal stratification turns out to destabilise the flow. This is explained by the fact that a stable stratification suppresses the secondary meridional flow, thus indirectly enhancing the primary rotation. The instability in the form of Taylor-Görtler rolls is consequently promoted. It is known from earlier studies that these rolls can be only excited by finite disturbances in the isothermal flow. A sufficiently strong thermal stratification transforms this non-linear bypass instability into …
Characterisation and mitigation of beam-induced backgrounds observed in the ATLAS detector during the 2011 proton-proton run
2013
This paper presents a summary of beam-induced backgrounds observed in the ATLAS detector and discusses methods to tag and remove background contaminated events in data. Triggerrate based monitoring of beam-related backgrounds is presented. The correlations of backgrounds with machine conditions, such as residual pressure in the beam-pipe, are discussed. Results from dedicated beam-background simulations are shown, and their qualitative agreement with data is evaluated. Data taken during the passage of unpaired, i.e. non-colliding, proton bunches is used to obtain background-enriched data samples. These are used to identify characteristic features of beam-induced backgrounds, which then are …
A measurement of material in the ATLAS tracker using secondary hadronic interactions in 7 TeV pp collisions
2016
Knowledge of the material in the ATLAS inner tracking detector is crucial in understanding the reconstruction of charged-particle tracks, the performance of algorithms that identify jets containing b-hadrons and is also essential to reduce background in searches for exotic particles that can decay within the inner detector volume. Interactions of primary hadrons produced in pp collisions with the material in the inner detector are used to map the location and amount of this material. The hadronic interactions of primary particles may result in secondary vertices, which in this analysis are reconstructed by an inclusive vertex-finding algorithm. Data were collected using minimum-bias trigger…
Optical Frequency Combs Generated in Silica Microspheres in the Telecommunication C-, U-, and E-Bands
2021
Optical frequency combs (OFCs) generated in microresonators with whispering gallery modes are demanded for different applications including telecommunications. Extending operating spectral ranges is an important problem for wavelength-division multiplexing systems based on microresonators. We demonstrate experimentally three spectrally separated OFCs in the C-, U-, and E-bands in silica microspheres which, in principle, can be used for telecommunication applications. For qualitative explanation of the OFC generation in the sidebands, we calculated gain coefficients and gain bandwidths for degenerate four-wave mixing (FWM) processes. We also attained a regime when the pump frequency was in t…