Nonlinear instability analysis of a vertical cylindrical magnetic sheet

Document Type : Research Paper


1 Department of Mathematics and Computer Science, Faculty of Science, Beni-Suef University, Egypt

2 Department of Mathematics, Faculty of Education, Ain Shams University, Roxy, Cairo, Egypt



This paper concerns with the nonlinear instability analysis of double interfaces separated three perfect, incompressible cylindrical magnetic fluids. The cylindrical sheet is acted upon by an axial  uniform magnetic field. The current nonlinear approach depends mainly on solving the linear governing equations of motion and subjected to the appropriate nonlinear boundary conditions. This procedure resulted in two nonlinear characteristic equations governed the behavior of the interfaces deflection. By means of the Taylor expansion, together with the multiple time scales, technique, the stability analysis of linear as well as the nonlinear is achieved. The linear stability analysis reveals a quadratic dispersion equation in the square of growth rate frequency of the surface wave. On the other hand, the nonlinear analysis is accomplished by a coupled nonlinear Schrödinger equation of the evolution amplitudes of the surface waves. The stability criteria resulted in a polynomial of the eleventh degree in the square of the magnetic field strength, together with resonance transition curves. Several special cases are reported upon appropriate data choices. The stability criteria are numerically discussed, at which regions of stability and instability are identified. In the stability profile, the magnetic field intensity is plotted versus the wave number. The influences of the parameters on the stability are addressed. The nonlinear stability approach divides the phase plane into several parts of stability/instability. The nonlinear stability shows an in contrast mechanism of the role of the sheet thickness.