A Forward-Speed Body-Exact Strip Theory

This paper develops an extension to the body-exact strip theory of Bandyk, Beck, and Zhang [1–8], focused on improved prediction of forward-speed effects. One of the known limitations of standard strip theory is the treatment of forward speed terms. The free surface boundary conditions completely neglect the forward speed, which is usually justified by the argument of high-frequency oscillations. The pressure equation on the body includes a speed-dependent term that must computed, most commonly using the Ogilvie-Tuck theorem or numerical approximations. The strip theory variation described here circumvents these deficiencies by applying the 2D+T approach. The model assumes that each two-dimensional frame, in which a boundary value problem (BVP) is solved, remains fixed relative to an earth-fixed frame. The numerical model is based on a time-domain Rankine source method, using the same body-exact approximation as described in earlier work [1]. A suitable acceleration potential BVP is derived. Added mass and damping coefficients are calculated for two Wigley hulls, using the the standard body-exact approach and forward-speed 2D + T variant, and compared to existing model test and numerical data.

Implantation of various energy metallic ions on aluminium substrate using a table top laser driven ion source

Particle acceleration is an important tool in material modification and several other applications. There are multiple techniques to generate and accelerate ion beams. In the current research work, ions emitted from laser induced plasma were accelerated by employing a DC high voltage extraction assembly. The Nd:YAG laser (1064 nm) with 10 mJ energy and 12 ns pulse width was irradiated on Aluminum target. Thomson parabola technique using Solid State Nuclear Track Detector (CR-39) was employed for measurement of ions energy generated from laser induced plasma. In response to a stepwise increase in acceleration potential from 0–10 kV, an evident increase in energy, in the range 627–730 keV, was observed. In order to utilize this facility as an ion source, Aluminum was exposed to these ions. The Optical and AFM micrographs revealed that the damage produced by the ions on Al surfaces, become more prominent with the increase in ion energy. TRIM simulations were performed for the analysis of the damage at the irradiated samples. Changes in the total displacements, target vacancies and replacement collisions, calculated by TRIM simulation, were analyzed for ion irradiations with increasing ion energies.