Abeer Bakhsh

Richtmyer–Meshkov instability (RMI) occurs when a shock wave impulsively accelerates a perturbed density interface between different fluids. The present work investigates the suppression of RMI of double interfaces in terms of linear analysis in cylindrical geometry. An exponential increase/decrease in a growth rate is related to the Rayleigh–Taylor instability that occurs without a magnetic field as the lighter fluid penetrates the heavier one. The research program of inertial confinement fusion is one of the advanced applications where fluid mixing is the main mechanize of producing energy. The investigations represent the effects of different Atwood numbers or magnetic strengths on the suppression of the instabilities. Three different cases are considered with the hydrodynamics and magnetohydrodynamics (MHD). In the MHD case, the instability's growth rate reduces proportion to the Atwood ratios or the strength of the magnetic field. Two waves are interfering and running paral...

We investigate the linear evolution of Richtmyer-Meshkov (RM) instability in the framework of an ideal two-fluid plasma model. The two-fluid plasma equations of motion are separated into a base state and a set of linearized equations governing the evolution of the perturbations. Different coupling regimes between the charged species are distinguished based on a non-dimensional Debye length parameter dD,0. When dD,0 is large, the coupling between ions and electrons is sufficiently small that the induced Lorentz force is very weak and the two species evolve as two separate fluids. When dD,0 is small, the coupling is strong and the induced Lorentz force is strong enough that the difference between state of ions and electrons is rapidly decreased by the force. As a consequence, the ions and electrons are tightly coupled and evolve like one fluid. The temporal dynamics is divided into two phases: an early phase wherein electron precursor waves are prevalent, and a post ion shockinterface...

Linear Analyses of Magnetohydrodynamic Richtmyer-Meshkov Instability in Converging Geometry Abeer Habeeb Allah Bakhsh We investigate the Richtmyer-Meshkov instability (RMI) that occurs when an incident shock impulsively accelerates the interface between two different fluids. RMI is important in many technological applications such as Inertial Confinement Fusion (ICF) and astrophysical phenomena such as supernovae. We consider RMI in the presence of the magnetic field in converging geometry through both simulations and analytical means in the framework of ideal magnetohydrodynamics (MHD). In this thesis, we perform linear stability analyses via simulations in the cylindrical geometry, which is of relevance to ICF. In converging geometry, RMI is usually followed by the Rayleigh-Taylor instability (RTI). We show that the presence of a magnetic field suppresses the instabilities. We study the influence of the strength of the magnetic field, perturbation wavenumbers and other relevant pa...

We investigate the linear stability of both positive and negative Atwood ratio interfaces accelerated either by a fast magnetosonic or hydrodynamic shock in cylindrical geometry. For the magnetohydrodynamic (MHD) case, we examine the role of an initial seed azimuthal magnetic field on the growth rate of the perturbation. In the absence of a magnetic field, the Richtmyer–Meshkov growth is followed by an exponentially increasing growth associated with the Rayleigh–Taylor instability (RTI). In the MHD case, the growth rate of the instability reduces in proportion to the strength of the applied magnetic field. The suppression mechanism is associated with the interference of two waves running parallel and antiparallel to the interface that transport vorticity and cause the growth rate to oscillate in time with nearly a zero mean value.

We investigate the linear evolution of the Richtmyer–Meshkov instability (RMI) in the framework of an ideal two-fluid plasma model. The two-fluid plasma equations of motion are separated into a base state and a set of linearized equations governing the evolution of the perturbations. Different coupling regimes between the charged species are distinguished based on a non-dimensional Debye length parameter [Formula: see text]. When [Formula: see text] is large, the coupling between ions and electrons is sufficiently small that the induced Lorentz force is very weak and the two species evolve as two separate fluids. When [Formula: see text] is small, the coupling is strong and the induced Lorentz force is strong enough that the difference between state of ions and electrons is rapidly decreased by the force. As a consequence, the ions and electrons are tightly coupled and evolve like one fluid. The temporal dynamics is divided into two phases: an early phase wherein electron precursor ...

A linear stability analysis is performed for the onset of Marangoni convection in a horizontal layer of a nanofluid heated from below and affected by rotation. The top boundary of the layer is assumed to be impenetrable to nanoparticles with their distribution being determined from a conservation condition while the bottom boundary is assumed to be a rigid surface with fixed temperature. The motion of the nanoparticles is characterized by the effects of thermophoresis and Brownian diffusion. A modification model is used in which the effects of Brownian diffusion and thermophoresis are taken into consideration by new expressions in the nanoparticle mass flux. Also, material properties of the nanofluid are modelled by non-constant constitutive expressions depending on nanoparticle volume fraction. The steady-state solution is shown to be well approximated by an exponential distribution of the nanoparticle volume fraction. The Chebyshev-Tau method is used to obtain the critical thermal...