STRATEGIES FOR THE EVALUATION OF THE FLUID-DYNAMIC ACOUSTIC POWER PRODUCED BY AN ORIFICE

A novel approach to numerically estimating the acoustic power produced by gas flow through control devices is presented. The procedure is based on the simulation of stationary fluid flow by means of the Reynolds Averaged Navier-Stokes (RANS) equations employing Computational Fluid Dynamics (CFD) techniques. An appropriate expression for the acoustic power density as defined by existing literature allows to obtain the acoustic power by integrating over an aptly-defined source region. A discussion of the results obtained for a single-hole orifice plate through the proposed and the reference international standards’ procedure follows

Combining UML and formal notations for modelling real-time systems

This article explores a dual approach to real-time software development. Models are written in UML, as this is expected to be relatively easy and economic. Then models are automatically translated into a formal notation that supports the verification of properties such as safety, utility, liveness, etc. In this way, developers can exploit the advantages of formal notations while skipping the complex and expensive formal modelling phase. The proposed approach is applied to the Generalised Railroad Crossing (GRC) problem, one of the best known benchmarks proposed in the literature. A UML model of the GRC is built, and then translated into TRIO (a first order temporal logic). The resulting specification properties are tested by a history checking tool which exploits the formality of TRIO. The work described here highlights the shortcomings of UML as a real-time modelling language, proposes enhancements and workarounds to overcome UML limitations, and demonstrates the viability of using UML as a front-end for a formal real-time notation. By translating the GRC model into TRIO, we also give formal semantics to some of the UML constructs