Wind tunnel model surface gauge for measuring roughness

The optical inspection of surface roughness research has proceeded along two different lines. First, research into a quantitative understanding of light scattering from metal surfaces and into the appropriate models to describe the surfaces themselves. Second, the development of a practical instrument for the measurement of rms roughness of high performance wind tunnel models with smooth finishes. The research is summarized, with emphasis on the second avenue of research

Parametric variation of a coupled pendulum-oscillator system using real-time dynamic substructuring

In this paper, we present results from real-time dynamic substructuring tests used to model the dynamics of a coupled pendulum–oscillator system. The substructuring technique is particularly suitable for systems where the nonlinear and linear parts of the system can be separated. The nonlinear part is built full size and tested physically (the substructure) while the linear part is simulated numerically. Then, in order to replicate the dynamics of the complete system the substructure and the numerical model must be coupled in real time. In this study, we demonstrate how real-time dynamic substructure testing can be used to model systems with strongly nonlinear behaviour using parametric variation. We show that the substructuring results give good qualitative and quantitative agreement with purely numerical simulations of the complete system for a range of parameters values. This includes single parameter bifurcation diagrams, some of which cannot be obtained from a full physical experiment. We also briefly discuss the effects of delay and noise on the stability of the substructured system, and how these effects can be mitigated. Copyright © 2006 John Wiley & Sons, Ltd