Added mass

About: Added mass is a research topic. Over the lifetime, 2849 publications have been published within this topic receiving 47899 citations.

Tailoring Beam Mechanics Towards Enhancing Detection of Hazardous Biological Species

Abstract: Microcantilever based sensors have been widely employed for measuring or detecting various hazardous chemical agents and biological agents. Although they have been successful in detecting agents of interest, researchers desire to improve their performance by enhancing their mass sensitivity towards developing “detect to warn” detection capabilities. Moreover, there has been little work aimed at tailoring beam mechanics as a means to enhance mass sensitivity. In this paper, a numerical study is performed to assess the influence of microcantilever geometry on mass sensitivity in order to improve these devices for better detection of hazardous biological agents in liquid environments. Modal analysis was performed on microcantilevers of different geometries and shapes using ANSYS software and compared to the basic rectangular shaped microcantilever structures employed by most researchers. These structures all possessed a 50 μm length, 0.5 μm thickness and 25 μm width where the cantilever is clamped to the substrate, and were analyzed for their basic resonance frequency as well as the frequency shift for the attachment of a 0.285 pg of mass attached on their surfaces. These numerical results indicated that two parameters dominate their behavior, (1) the effective mass of the cantilever at the free end and (2) the clamping width at the fixed end. The ideal geometry was a triangular shape, which minimized effective mass and maximized clamping width, resulting in an order of magnitude increase in mass sensitivity (1,775 Hz/pg) over rectangular shaped cantilevers (172 Hz/pg) of identical length and clamping width. The most practical geometry was triangular shaped cantilever with a square pad at the free end for capturing the agent of interest. This geometry resulted in a mass sensitivity of 628 Hz/pg or nearly a 4-fold increase in performance over their rectangular counterparts.

Influence of Viscous Effects on the Hydrodynamics of Ship-Like Sections Undergoing Symmetric and Anti-Symmetric Motions, Using RANS

Abstract: The aim of this investigation is to assess the influence of viscous effects on the predicted hydrodynamic coefficients for a range of ship-like sections, such as rectangular, triangular, chine and bulbous. Hydrodynamic coefficients, of added mass or inertia and fluid damping, for two-dimensional sections harmonically heaving, swaying and rolling at the undisturbed free surface are obtained using the ANSYS-CFX11.0 RANS solver, for a range of frequencies of oscillation. All predictions are compared with available experimental measurements and other numerical predictions (potential flow and RANS). It is concluded from these comparisons that the proposed RANS approach can offer a better prediction for the hydrodynamic coefficients when viscous effects become significant, in particular for sway and roll motions. It is important that a reliable and systematic approach is adopted for the application of the unsteady free surface RANS methodology.