Search results for "Fluid Dynamic"
showing 10 items of 1034 documents
Monoclinic model shear zones
1998
Abstract Although many ductile shear zones are supposed to have developed by approximately simple shear flow, some must have formed under different conditions. A few types of such ‘non-simple shear zones’ have been proposed in the literature such as transpression-, transtension- and stretching-shear zones. This paper presents a full three-dimensional kinematic model of shear zones with monoclinic flow geometry. Monoclinic shear zone types can be classified according to flow parameters, and according to the geometry and orientation of accumulating finite strain. Modelling of finite strain accumulation shows that a number of unusual and potentially problematic structural features may develop …
The formation of large quartz veins by rapid ascent of fluids in mobile hydrofractures
2001
Abstract This paper aims to resolve two main problems related to the formation of quartz veins: (1) the predominance of quartz veins at shallow crustal levels and not deeper in the crust, close to the source of metamorphic fluids where the temperature sensitivity of quartz solubility is much higher than at lower, upper-crustal temperatures and (2) the formation of very large 100–1000 m scale quartz veins that would require huge amounts of fluid flow in current models of vein formation. It is proposed here that these problems are resolved by the recognition of very fast (m/s) mobile hydrofracture ascent of batches of fluid. Mobile hydrofractures are fluid-filled fractures that propagate at t…
Effect of pH on the mobility of the herbicide MCPA in a sand-goethite column: 1D and 2D reactive transport modeling
2018
Abstract Adsorption and transport of the herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA) in a homogeneous sand-goethite system were investigated as a function of pH. Interaction of MCPA with the solid surface was geochemically modeled according to the charge distribution multisite complexation (CD-MUSIC) approach. Based on this calibration, retardation of MCPA transport in column experiments was significantly underestimated by conventional 1D simulations. As a new approach, Positron Emission Tomography (PET) was employed to analyze the flow field, using 18F− as a radiotracer. The observed heterogeneity was reproduced in 2D simulations assuming increased permeability and porosity at the…
Group analysis and similarity solutions of the compressible boundary layer equations
1989
In this paper the application of Lie's methods to the equations of the laminar boundary layer is discussed. The momentum and energy equations in Prandtl's form are considered for a steady, viscous, compressible laminar flow with non zero pressure gradient, variable viscosity and thermal conductivity. Group analysis yields similarity solutions for given pressure distributions and particular values of the invariance group parameters (group classification). Crocco's transformation is obtained for the infinite-dimensional group of the Lie's algebra admitted by the equations.
Numerical simulation of transcatheter mitral valve replacement: The dynamic implication of LVOT obstruction in the valve-in-ring case.
2022
Transcatheter mitral valve replacement (TMVR) has been used for “off-label” treatment when annuloplasty band ring for mitral repair fails. However, the complex anatomy and function of the mitral valve may lead to fatal complications as a result of the left ventricular outflow tract (LVOT) obstruction in TMVR. We report the structural and hemodynamic response of LVOT obstruction resulting from TMVR with the Edwards SAPIEN 3 Ultra (S3) device. We modified the original Living Heart Human Model (LHHM) to account for a failed mitral valve with an annuloplasty band ring and simulated the cardiac beating condition in the setting of S3 device implantation. Findings demonstrated a high dynamic behav…
Constant circulation sequences of binary neutron stars and their spin characterization
2018
For isentropic fluids, dynamical evolution of a binary system conserves the baryonic mass and circulation; therefore, sequences of constant rest mass and constant circulation are of particular importance. In this work, we present the extension of our Compact Object CALculator (\cocal{}) code to compute such quasiequilibria and compare them with the well-known corotating and irrotational sequences, the latter being the simplest, zero-circulation case. The circulation as a measure of the spin for a neutron star in a binary system has the advantage of being exactly calculable since it is a local quantity. To assess the different measures of spin, such as the angular velocity of the star, the q…
Using evolutionary algorithms to model relativistic jets
2019
High-resolution Very-Long-Baseline Interferometry observations of NGC 1052 show a two sided jet with several regions of enhanced emission and a clear emission gap between the two jets.This gap shrinks with increasing frequency and vanishes around $\nu\sim43$ GHz. The observed structures are due to both the macroscopic fluid dynamics interacting with the surrounding ambient medium including an obscuring torus and the radiation microphysics. In this paper we investigate the possible physical conditions in relativistic jets of NGC 1052 by directly modelling the observed emission and spectra via state-of-the-art special-relativistic hydrodynamic (SRHD) simulations and radiative transfer calcula…
Dynamical efficiency of collisionless magnetized shocks in relativistic jets
2010
The so-called internal shock model aims to explain the light-curves and spectra produced by non-thermal processes originated in the flow of blazars and gamma-ray bursts. A long standing question is whether the tenuous collisionless shocks, driven inside a relativistic flow, are efficient enough to explain the amount of energy observed as compared with the expected kinetic power of the outflow. In this work we study the dynamic efficiency of conversion of kinetic-to- thermal/magnetic energy of internal shocks in relativistic magnetized outflows. We find that the collision between shells with a non-zero relative velocity can yield either two oppositely moving shocks (in the frame where the co…
Periodic massloss from viscous accretion flows around black holes
2014
We investigate the behaviour of low angular momentum viscous accretion flows around black holes using Smooth Particle Hydrodynamics (SPH) method. Earlier, it has been observed that in a significant part of the energy and angular momentum parameter space, rotating transonic accretion flow undergoes shock transition before entering in to the black hole and a part of the post-shock matter is ejected as bipolar outflows, which are supposed to be the precursor of relativistic jets. In this work, we simulate accretion flows having injection parameters from the inviscid shock parameter space, and study the response of viscosity on them. With the increase of viscosity, shock becomes time dependent …
QUANTUM EFFECTS IN ACOUSTIC BLACK HOLES: THE BACKREACTION.
2004
We investigate the backreaction equations for an acoustic black hole formed in a Laval nozzle under the assumption that the motion of the fluid is one-dimensional. The solution in the near-horizon region shows that as phonons are (thermally) radiated the sonic horizon shrinks and the temperature decreases. This contrasts with the behaviour of Schwarzschild black holes, and is similar to what happens in the evaporation of (near-extremal) Reissner-Nordstrom black holes (i.e. infinite evaporation time). Finally, by appropriate boundary conditions the solution is extended in both the asymptotic regions of the nozzle.