ANALYSIS OF PLANAR MECHANISMS BY COMPUTER SUBROUTINE.

A suite of computer subroutines is described which allows rapid analysis of most types of planar mechanism by the writing of a simple computer programme. The analytical techniques of these subroutines are explained, and a worked example is presented to illustrate the use of the package, and to demonstrate its advantages in the calculation of inertia forces within a mechanism.

Enhanced reflection from arrays of silicon based inverted nanocones

We report enhanced reflection displayed by arrays of silicon based inverted nanocones. Theoretical studies suggest that such arrays display enhanced reflection and photonic band gaps within the optical and near infrared regions. Measured results show three to four fold enhancement in reflection and agree well with calculations. Such arrays can be used to enhance infrared reflection in photovoltaic devices which mostly contribute towards heating. © 2011 American Institute of Physics.

The local and global stability of confined planar wakes at intermediate Reynolds number

At high Reynolds numbers, wake flows become more globally unstable when they are confined within a duct or between two flat plates. At Reynolds numbers around 100, however, global analyses suggest that such flows become more stable when confined, while local analyses suggest that they become more unstable. The aim of this paper is to resolve this apparent contradiction by examining a set of obstacle-free wakes. In this theoretical and numerical study, we combine global and local stability analyses of planar wake flows at $\mathit{Re}= 100$ to determine the effect of confinement. We find that confinement acts in three ways: it modifies the length of the recirculation zone if one exists, it brings the boundary layers closer to the shear layers, and it can make the flow more locally absolutely unstable. Depending on the flow parameters, these effects work with or against each other to destabilize or stabilize the flow. In wake flows at $\mathit{Re}= 100$ with free-slip boundaries, flows are most globally unstable when the outer flows are 50 % wider than the half-width of the inner flow because the first and third effects work together. In wake flows at $\mathit{Re}= 100$ with no-slip boundaries, confinement has little overall effect when the flows are weakly confined because the first two effects work against the third. Confinement has a strong stabilizing effect, however, when the flows are strongly confined because all three effects work together. By combining local and global analyses, we have been able to isolate these three effects and resolve the apparent contradictions in previous work.