Temperature Rise Induced by a Rotating/Dithering Laser Beam on a Finite Solid

摘要

High energy laser weapons have been evolving progressively in recent years. These weapons deliver high-intensity beams to a target and can instantly destroy or burn it. They may cause potential threats to Navy ships, computer networks, guided missiles, and satellites in orbit. In order to reduce our military's vulnerability to high energy laser weapons, one possible countermeasure is to rotate or rock the object itself when it is hit by the laser beam. The main purpose of this thesis is to investigate the relationship between the speed of a rotating/dithering laser beam and the maximum temperature rise induced by the laser beam on a finite solid. We have investigated extensively the numerical solutions for the transient temperature rise in both one-dimensional (1-D) and twodimensional (2-D) finite solids due to rotating/dithering laser beams. Our mathematical approaches include the eigenfunction expansion method, the Crank-Nicolson method, the Fast Fourier Transform method, and COMSOL for 1-D and 2-D cases. We have employed COMSOL to solve the 3-D nonhomogeneous heat equation. This thesis provides the first study that we know of on the effect of rotating/dithering laser beams on a finite target. Our results are consistent with previous analytical studies on semi-infinite regions. The quantitative relationship between maximum temperature rise and laser beam rotating speed, which is presented in this thesis, can be used as a general guide for adjusting the speed of rotation of the target in order to prevent the maximum temperature rise from reaching the melting point of the target.