Doo-Sung Lee

Nonlinear dynamic buckling of orthotropic cylindrical shells subjected to rapidly applied loads

Dynamic buckling of an orthotropic cylindrical shell which is subjected to rapidly applied compression is considered. A nonlinear differential equation of Donnell–Karman type is derived with the initial imperfection taken into account. An energy method is used to obtain the equation of motion which is then solved numerically by means of a Runge-Kutta method. These numerical results show that the critical load is increased over the corresponding static case. An analytical solution is also obtained for the problem of hydrostatic pressure.

Nonlinear Kelvin–Helmholtz instability of fluid layers with mass and heat transfer

The nonlinear Kelvin–Helmholtz stability of the interface between the vapour and liquid phases of a fluid is studied when the phases are confined between two parallel lines, and when there is mass and heat transfer across the interface. The method of multiple time expansion is used for the investigation. The evolution of amplitude is shown to be governed by a nonlinear first-order differential equation. The stability criterion is discussed, and the region of stability is displayed graphically.

Nonlinear Kelvin–Helmholtz instability of cylindrical flow with mass and heat transfer

The nonlinear Kelvin–Helmholtz stability of the cylindrical interface between the vapour and liquid phases of a fluid is studied when the phases are enclosed between two cylindrical surfaces coaxial with the interface, and when there is mass and heat transfer across the interface. The method of multiple time expansion is used for the investigation. The evolution of amplitude is shown be governed by a nonlinear first-order differential equation. The stability criterion is discussed, and the region of stability is displayed graphically.

Nonlinear Rayleigh instability of cylindrical flow with mass and heat transfer

The nonlinear Rayleigh instability of the cylindrical interface between the vapour and liquid phases of a fluid is studied when the phases are enclosed between two cylindrical surfaces coaxial with the interface, and when there is mass and heat transfer across the interface. The method of multiple expansion is used for the investigation. The evolution of amplitude is shown to be governed by a first-order nonlinear differential equation. The stability criterion is discussed, and the region of stability is displayed graphically.

A long circular cylinder with a circumferential edge crack subjected to a uniform shearing stress

This paper contains an analysis of the stress distribution in a long circular cylinder of isotropic elastic material with a circumferential edge crack when it is deformed by the application of a uniform shearing stress. The crack with its center on the axis of the cylinder lies on the plane perpendicular to that axis, and the cylindrical surface is stress-free. By making a suitable representation of the stress function for the problem, the problem is reduced to the solution of a pair of singular integral equations. This pair of singular integral equations is solved numerically, and the stress intensity factor due to the effect of the crack size is tabulated.

Torsion of a long circular cylinder having a spherical cavity with a peripheral edge crack

The singular stress problem of a peripheral edge crack around a spherical cavity in a long circular cylinder under torsion is investigated. The problem is solved by using integral transforms and is reduced to the solution of two integral equations. The solution of these equations is obtained numerically by the method due to Erdogan, Gupta, and Cook, and the stress intensity factors, and crack opening displacements are displayed graphically.

Penny-shaped crack in a long circular cylinder subjected to a uniform shearing stress

This paper contains an analysis of the stress distribution in a long circular cylinder of elastic material containing a penny-shaped crack when it is deformed by the application of a uniform shearing stress. The crack with its center on the axis of the cylinder lies on the plane perpendicular to that axis, and the cylindrical surface is stress-free. By making a suitable representation of the stress function for the problem, the problem is reduced to the solution of a pair of Fredholm integral equations of second kind. These are solved numerically, and the percentage increase in the stress intensity factor due to the effect of the finite radius of the cylinder is presented in graphical form for various proximity ratios.

Nonlinear Instability of an Electrohydrodynamic Planar Jet

The nonlinear breakup of a fluid jet forming a plane sheet stressed at the surface by an electric field is studied. A third-order theory using the method of strained coordinates is applied to study the capillary instability of the jet. The time of breakup of the jet is obtained numerically.

CLASSIFICATION OF OBJECTS IN AN ACOUSTIC WAVEGUIDE BY INVERSION OF THE FARFIELD DATA

In this paper we investigate the unknown body problem in a waveguide. The Rayleigh conjecture states that every point on an illuminated body radiates sound from that point as if the point lies on its tangent sphere. This conjecture is the cornerstone of the intersecting canonical body approximation ICBA for solving the unknown body inverse problem. Therefore, the use of the ICBA requires that an analytical solution be known exterior to the sphere in the waveguide, which leads us to analytically compute the exterior solution for a sphere between two parallel plates. A least-squares matching of theoretical acoustic fields against the measured, scattered field permits a reconstruction of the unknown object.

Nonlinear Stability of a Cylindrical Interface with Mass and Heat Transfer

Abstract The nonlinear Rayleigh-Taylor stability of a cylindrical interface between vapor and the liquid phases of a fluid is studied when the phases are enclosed between two cylindrical surfaces coaxial with the interface, and when there is mass and heat transfer across the interface. The method of multiple time scale expansion is used for the investigation. A simple nondimensional parameter is found to characterize the stability of the system. Using this parameter, the region of stability is displayed graphically.