Large eddy simulations for fan-OGV broadband noise prediction

The work in this paper forms part of a project on the use of large eddy simulation (LES) for broadband rotor-stator interaction noise prediction. Here we focus on LES of the flow field near a fan blade trailing edge. The first part of the paper aims to evaluate LES suitability for predicting the near-field velocity field for a blunt NACA-0012 airfoil at moderate Reynolds numbers (2× 10 5 and 4× 10 5). Preliminary computations of turbulent mean and root-mean-square velocities, as well as energy spectra at the trailing edge, are compared with those from a recent experiment.1 The second part of the paper describes preliminary progress on an LES calculation of the fan wakes on a fan rig. 2 The CFD code uses a mixed element unstructured mesh with a median dual control volume. A wall-adapting local eddy-viscosity sub-grid scale model is employed. A very small amount of numerical dissipation is added in the numerical scheme to keep the compressible solver stable. Further results for the fan turbulentmean and RMS velocity, and especially the aeroacoustics field will be presented at a later stage. Copyright © 2008 by Qinling LI, Nigel Peake & Mark Savill.

Grid-refined LES predictions for Fan-OGV broadband noise

This work forms part of a project on the use of large eddy simulation (LES) for broadband rotor-stator interaction noise prediction. In this paper, we focus on LES calculations of noise sources on and close to a blade trailing edge. We consider two test cases; one an isolated NACA0012 airfoil in flow, and the other an industry-standard rotating fan. In the first case, turbulent mean and RMS velocities and energy spectra at different locations are compared with those from experiment. 1,2The sound generated by the unsteady pressure fluctuations on the airfoil surface and by the flow turbulence will be predicted using a Ffowcs Williams Hawkings (FW-H) surface. In the second case, unsteady flow and acoustic fields around the blade passage 3 are presented for a refined mesh, and the rotor-stator tonal noise will be predicted by using the rotor-wake mean velocity profile and the methodology described in Lloyd & Peake 4. Copyright © 2009 by Qinling Li, Nigel Peake & Mark Savill.

Rotor - Stator broadband noise prediction

In this paper a semi analytic model for rotor - stator broadband noise is presented. The work can be split into two sections. The first examines the distortion of the rotor wake in mean swirling flow, downstream of the fan. Previous work by Cooper and Peake4 is extended to include dissipative effects. In the second section we consider the interaction of this gust with the downstream stator row. We examine the way in which an unsteady pressure field is generated by the interaction of this wake flow with the stator blades and obtain estimates for the radiated noise. A new method is presented to extend the well known LINSUB code to the third dimension to capture the effect of the spanwise wavenumber and stator lean and sweep. Copyright © 2008 by Adrian Lloyd and Nigel Peake.

GSPS photonic analogue to digital conversion system using broadband continuous wave source

An 80 GSPS photonic ADC system is demonstrated, using broadband MLL and dispersive fibre to form a continuous waveform with time-wavelength mapping, and AWG to channelise. Tests are carried out for RF signals up to 10GHz. © 2005 Optical Society of America.

The Politics of Internet Regulation in Brazil : dynamics, factors, and actors in broadband policy

In May 2010, Brazil joined the roll of nations with a National Broadband Plan. The Decree nº 7,175/2010 had implemented a program that aimed to offer 30 million permanent broadband accesses until 2014 and established its main goals, such as accelerating economic and social development, promoting digital inclusion, reducing social and regional inequalities, promoting a generation of employment and income, and expanding electronic government services. However, the broadband access in Brazil is limited, expensive, and centralized in the main urban centres. Despite the fast growth in the past years due to mobile internet access, the market is still concentrated in the local incumbent operators that currently provide mobile services, landline services and Paid-TV services, resulting in a high level of market verticalization. The following dissertation investigates the constraint of broadband access development, the dynamics, the actors, and the factors that have delayed the roll-out of broadband services in Brazil. The study also promotes reflections about the challenge posed by the media, by costumers associations and by public opinion as critical observers of the policy making process. This research examines on the political influence towards regulation to determine the way policy will benefit interest groups. Many interviews have been conducted in order to understand the forces which have been acting in the telecommunications in Brazil after privatization, in 1998. This study aims to provide a better understanding of telecommunications regulatory process in Brazil, in order to help the country finding an adequate policy which can lead to the implementation of a broadband roll-out. The universal broadband access is the only way to benefit the whole society in Brazil with a satisfactory level of education and create more jobs and economic development regarding the plenty use of Information and Communications Technology (ICT).