Numerical Simulation of an Oscillating Cylinder in Cross-Flow at a Reynolds Number of 10,000: Forced and Free Oscillations

In the present work, numerical simulations of flow past a circular cylinder in uniform cross-flow are investigated for three different cases: (i) a stationary cylinder, (ii) forced oscillations of a cylinder and (iii) free oscillations of a cylinder. All three cases were studied using a 2D CFD RANS code, at a Reynolds number Re = 10,000. The method adopted here is based on the Finite Volume Method using the commercial CFD package Ansys Fluent 14 with appropriate turbulence models. Comparisons with available experimental and numerical data, for all cases investigated, show that the simulations capture essential features of the fluid-structure interaction. These comparisons include drag and lift coefficients, Strouhal number, pressure distribution, as well as amplitude of motion and frequency ratio.

JET CONFINEMENT BY NONLINEAR MAGNETO-TORSIONAL OSCILLATIONS

Many quasars and active galactic nuclei are connected with long, thin jets. When observed with high angular resolution, these jets show a structure with bright knots separated by relatively dark regions. We consider magnetic collimation, connected with torsional oscillations of a cylinder with elongated magnetic field, and periodically distributed initial rotation around the cylinder axis. The stabilizing azimuthal magnetic field is created here by torsional oscillations. An approximate, simplified model is developed. The parameters for which jets may be stabilized by torsional oscillations are estimated quantitatively.