The effect of wall compliance on the Goertler vortex instability

The stability of the flow of a viscous incompressible fluid over a curved compliant wall to longitudinal Goertler vortices is investigated. The compliant wall is modeled by a particularly simple equation relating the induced wall displacement to the pressure in the overlying fluid. Attention is restricted to the large Goertler number regime; this regime being appropriate to the most unstable Goertler mode. The effect of wall compliance on this most unstable mode is investigated

On the nonlinear development of the most unstable Goertler vortex mode

The nonlinear development of the most unstable Gortler vortex mode in boundary layer flows over curved walls is investigated. The most unstable Gortler mode is confined to a viscous wall layer of thickness O(G -1/5) and has spanwise wavelength O(G 11/5); it is, of course, most relevant to flow situations where the Gortler number G is much greater than 1. The nonlinear equations covering the evolution of this mode over an O(G -3/5) streamwise lengthscale are derived and are found to be of a fully nonparallel nature. The solution of these equations is achieved by making use of the numerical scheme used by Hall (1988) for the numerical solution of the nonlinear Gortler equations valid for O(1) Gortler numbers. Thus, the spanwise dependence of the flow is described by a Fourier expansion, whereas the streamwise and normal variations of the flow are dealt with by employing a suitable finite difference discretization of the governing equations. Our calculations demonstrate that, given a suitable initial disturbance, after a brief interval of decay, the energy in all the higher harmonics grows until a singularity is encountered at some downstream position. The structure of the flowfield as this singularity is approached suggests that the singularity is responsible for the vortices, which are initially confined to the thin viscous wall layer, moving away from the wall and into the core of the boundary layer

Leaving Work, Leaving Home: Job Loss and Socio-Geographic Mobility in Canada

Poster Presentation The recent economic downturn magnified a routine occurrence in the Canadian labor market: involuntary job loss resulting from an employer downsizing, moving, or going out of business. Yet, in recent decades, even in times of economic expansion, rates of involuntary job loss have persisted across a wide-range of demographic and labor market groups. Moving is one way individuals may respond to job loss, either to relocate to cheaper housing or in search of work. Drawing on data from the 1996-2010 Survey of Labour and Income Dynamics, this article examines the relationship between involuntary job loss and geographic mobility in Canada, and further provides evidence on the types of neighborhoods to which individuals move. I find that involuntary job loss is associated with short- and long-distance mobility and increased risk of selection into materially deprived neighborhoods. Together, the findings establish job loss as both a key life course transition motivating residential mobility and long-distance migration in Canada, and as a trigger event that initiates entry into high deprivation areas

On the receptivity problem for Goertler vortices: Vortex motions induced by wall roughness

The receptivity problem for Goertler vortices induced by wall roughness is investigated. The roughness is modelled by small amplitude perturbations to the curved wall over which the flow takes place. The amplitude of these perturbations is taken to be sufficiently small for the induced Goertler vortices to be described by linear theory. The roughness is assumed to vary in the spanwise direction on the boundary layer lengthscale, while in the flow direction the corresponding variation is on the lengthscale over which the wall curvature varies. In fact the latter condition can be relaxed to allow for a faster streamwise roughness variation so long as the variation does not become as fast as that in the spanwise direction. The function which describes the roughness is assumed to be such that its spanwise and streamwise dependences can be separated; this enables progress by taking Fourier or Laplace transforms where appropriate. The cases of isolated and distributed roughness elements are investigated and the coupling coefficient which relates the amplitude of the forcing and the induced vortex amplitude is found asymptotically in the small wavelength limit. It is shown that this coefficient is exponentially small in the latter limit so that it is unlikely that this mode can be stimulated directly by wall roughness. The situation at 0(1) wavelengths is quite different and this is investigated numerically for different forcing functions. It is found that an isolated roughness element induces a vortex field which grows within a wedge at a finite distance downstream of the element. However, immediately downstream of the obstacle the disturbed flow produced by the element decays in amplitude. The receptivity problem at larger Goertler numbers appropriate to relatively large wall curvature is discussed in detail

Understanding the Use of Inheritance with Visual Patterns

International audienceThe goal of this work is to visualize inheritance in object-oriented programs to help its comprehension. We propose a single, compact view of all class hierarchies at once using a custom Sunburst layout. It enables to quickly discover interesting facts across classes while preserving the essential relationship between parent and children classes. We explain how standard inheritance metrics are mapped into our visualization. Additionally, we define a new metric characterizing similar children classes. Using these metrics and the proposed layout, a set of common visual patterns is derived. These patterns allow the programmer to quickly understand how inheritance is used and provide answers to some essential questions when performing program comprehension tasks. Our approach is evaluated through a case study that involves examples from large programs, demonstrating its scalability

Expression and Composition of Design Patterns with AspectJ

National audienceDesign patterns are well-known couples of problems-solutions for software engineer- ing. By nature, they often lack support from languages and this further complicates the study of their composition in the code. Aspect-oriented languages provide new mechanisms for modula- rization, which can help to improve design patterns implementation. (Hannemann et al., 2002) is the first extensive study of patterns aspectization with AspectJ. We notice some AspectJ idioms are needed in order to implement object relationships. We give a more reusable VISITOR pat- tern. We highlight a reusable composition of COMPOSITE and VISITOR patterns and expressive interactions of the OBSERVER pattern with a tree structure. We thus show that modularization by aspects helps composition of design patterns

There’s a wage hierarchy based on sexual orientation

Lesbians earn more than straight women (but less than all men), write Sean Waite and Nicole Denie

The dominant wave mode within a trailing line vortex

We identify the dominant, or most unstable, wave mode for the flow in a trailing line vortex. This dominant mode is found to reside in a wavenumber regime between that of inviscid wave modes and the viscous upper branch neutral wave modes. A reevaluation of the growth rate in the vicinity of the upper branch of the curve of neutral stability allows us to predict the neutral value of the azimuthal and axial wavenumber as a function of the imposed swirl within the trailing line vortex.James P. Denier and Jillian A. K. Stot

Proceedings of the 3rd Workshop on FAMIX and MOOSE in Software Reengineering (FAMOOSr'09)

International audienceThe goal of the FAMOOSr workshop is to strengthen the community of researchers and practitioners who are working in re- and reverse engineering, by providing a forum for building future research using Moose and FAMIX as shared infrastructure. Research should be collaborative and supported by tools. The increasing amount of data available about software systems poses new challenges for reengineering research, as the proposed approaches need to scale. In this context, concerns about meta-modeling and analysis techniques need to be augmented by technical concerns about how to reuse and how to build upon the efforts of previous research. That is why Moose is an open-source software for researchers to build and share their analysis, meta-models, and data. Both FAMIX and Moose started in the context of FAMOOS, a European research project on object-oriented frameworks. Back in 1997 Moose was as a simple implementation of the FAMIX meta-model, which was a language independent meta-model for object-oriented systems. However over the past decade, Moose has been used in a growing number of research projects and has evolved to be a generic environment for various reverse and reengineering activities. In the same time, FAMIX was extended to support emerging research interest such as dynamic analysis, evolution analysis, identifier analysis, bug tracking analysis, or visualization. Recent work includes analysis of software architecture and semantic annotations. Currently, several research groups are using Moose as a platform, or FAMIX as a meta-model, and other groups announced interest in using them in the future

How your sexual orientation can affect how much you earn

Despite recent strides toward equality, labor markets are often stratified on gender and racial grounds. Using Canadian Census data, Sean Waite and Nicole Denier find that these wage gaps extend to sexual minorities; even when employed in lucrative occupations, gay men and lesbians earn significantly less than straight men. They also find that while straight women’s pay is penalised, the presence of children and marriage have no effect on the earnings of either gay men or lesbians in conjugal relationships