We study strong-gravity effects on modulation of radiation emerging from accreting compact objects as a possible mechanism for flux modulation in QPOs. We construct a toy model of an oscillating torus in the slender approximation assuming thermal bremsstrahlung for the intrinsic emissivity of the medium and we compute observed (predicted) radiation signal including contribution of indirect (hig...

Though it is well established that magnetic fields effectively transport angular momentum in an accretion disk, it is far from clear if magnetic fields also effectively transport or dissipate energy in the meantime. In this paper we use a simple model to study the dynamical effects of magnetic fields in an accretion disk around a Kerr black hole, trying to understand the transportation of angul...

We study reaction fronts described by the Kuramoto-Sivashinsky equation subject to a Poiseuille flow. The fronts propagate with or against the flow located inside a two-dimensional slab. Steady front profiles can be flat, axisymmetric, or nonaxisymmetric, depending on the gap between the plates and the average flow speed. We first obtain the steady front solutions, later executing a linear stab...

The velocity fluctuations in a spherical shell arising from sinusoidal perturbations of a Keplerian shear flow with a free amplitude parameter ε are studied numerically by means of fully 3D nonlinear simulations. The investigations are performed at high Reynolds numbers, i.e. 3000 < Re < 5000. We find Taylor-Proudman columns of large eddies parallel to the rotation axis for sufficiently strong ...

Computations and experimental validation were conducted to obtain flow field over an axisymmetric cavity with different front wall inclinations at a freestream Mach number of 2.0. Flow oscillation in and around the cavities may incur a damaging effect on the stable flight of the aircraft and store releases. Aero-acoustic from the oscillating flow induces vibration in the local bay structure and...

This report describes an experimental and numerical study of impinging, incompressible, axisymmetric, laminar jets, where the jet axis of symmetry is aligned normal to the wall. Particle Streak Velocimetry (PSV) is used to measure axial velocities along the centerline of the flow field. The jet-nozzle pressure drop is measured simultaneously and determines the Bernoulli velocity. The flowfield ...

The effect of viscosity ratio (λ, defined as viscosity of surrounding medium/viscosity of fluid jet) on stability of axisymmetric (m=0) and asymmetric (m=1) modes of perturbation on a liquid-liquid jet in presence of radial electric field (E0 ), is studied using linear stability analysis. The viscosity ratio is shown to have a damping effect on both the modes of perturbation. However the effect...

In this paper an upwind algorithm based on Roe’s scheme is presented for solution of PNS equations. Non iterative-implicit method using finite volume technique is used. The main advantage of this approach, in comparison with similar upwind methods, is reduction of oscillations around sonic line. This advantage causes the present method to be able to analyze supersonic flows with free stream Mac...

Small 3D magnetic perturbations have many interesting and useful effects on tokamak and quasi-symmetric stellarator plasmas. Plasma transport equations that include these effects, most notably on diamagnetic-level toroidal plasma rotation, have recently been developed. The 3D magnetic perturbations and their plasma effects can be classified according to their toroidal mode number n. Low n non-r...

Centrifugally driven interchange instabilities are observed in a laboratory plasma confined by a dipole magnetic field. The instabilities appear when an equatorial mesh is biased to drive a radial current that causes rapid axisymmetric plasma rotation. The observed instabilities are quasicoherent in the laboratory frame of reference; they have global radial mode structures and low azimuthal mod...