Calculation of droplet deformation at intermediate Reynolds number using a Volume of Fluid technique

The deformation of a droplet or bubble in simple extensional flow fields is investigated at intermediate Reynolds number using a Volume-of-Fluid (VOF) numerical algorithm (MAC2) developed by Rudman. The results of an evaluation study of the MAC2 algorithm for such flows are presented. The final steady shapes of droplets in axisymmetric extensional flow fields determined by MAC2 are compared with the published numerical results of Ramaswamy and Leal. This work forms the initial stage of a more comprehensive study of droplet deformation in time-dependent shear fields experienced by drops flowing through devices (e.g.\ homogenisers) designed for droplet breakup

“I h 8 u”: Findings from a five-year study of text and e-mail bullying

Copyright @ 2010 British Educational Research Association. The final version of this article is available at the link below.This study charts reports of nasty or threatening text and e-mail messages received by students in academic years 7 and 8 (11-13 years of age) attending 13 secondary schools in the North of England between 2002-2006. Annual surveys were undertaken on behalf of the local education authority (LEA) to monitor bullying. Results indicated that, over five years, the number of pupils receiving one or more nasty or threatening text messages or e-mails increased significantly, particularly among girls. However, receipt of frequent nasty or threatening text and e-mail messages remained relatively stable. For boys, being a victim of direct-physical bullying was associated with receiving nasty or threatening text and e-mail messages; for girls it was being unpopular among peers. Boys received more hate-related messages and girls were primarily the victims of name-calling, Findings are discussed with respect to theoretical and policy developments, and recommendations for future research are offered

Assessing the performance of maternity care in Europe: A critical exploration of tools and indicators

Background: This paper critically reviews published tools and indicators currently used to measure maternity care performance within Europe, focusing particularly on whether and how current approaches enable systematic appraisal of processes of minimal (or non-) intervention in support of physiological or "normal birth". The work formed part of COST Actions IS0907: "Childbirth Cultures, Concerns, and Consequences: Creating a dynamic EU framework for optimal maternity care" (2011-2014) and IS1405: Building Intrapartum Research Through Health - an interdisciplinary whole system approach to understanding and contextualising physiological labour and birth (BIRTH) (2014-). The Actions included the sharing of country experiences with the aim of promoting salutogenic approaches to maternity care. Methods: A structured literature search was conducted of material published between 2005 and 2013, incorporating research databases, published documents in english in peer-reviewed international journals and indicator databases which measured aspects of health care at a national and pan-national level. Given its emergence from two COST Actions the work, inevitably, focused on Europe, but findings may be relevant to other countries and regions. Results: A total of 388 indicators were identified, as well as seven tools specifically designed for capturing aspects of maternity care. Intrapartum care was the most frequently measured feature, through the application of process and outcome indicators. Postnatal and neonatal care of mother and baby were the least appraised areas. An over-riding focus on the quantification of technical intervention and adverse or undesirable outcomes was identified. Vaginal birth (no instruments) was occasionally cited as an indicator; besides this measurement few of the 388 indicators were found to be assessing non-intervention or "good" or positive outcomes more generally. Conclusions: The tools and indicators identified largely enable measurement of technical interventions and undesirable health (or pathological medical) outcomes. A physiological birth generally necessitates few, or no, interventions, yet most of the indicators presently applied fail to capture (a) this phenomenon, and (b) the relationship between different forms and processes of care, mode of birth and good or positive outcomes. A need was identified for indicators which capture non-intervention, reflecting the reality that most births are low-risk, requiring few, if any, technical medical procedures

Putting ourselves in another’s skin: using the plasticity of self-perception to enhance empathy and decrease prejudice

The self is one the most important concepts in social cognition and plays a crucial role in determining questions such as which social groups we view ourselves as belonging to and how we relate to others. In the past decade, the self has also become an important topic within cognitive neuroscience with an explosion in the number of studies seeking to understand how different aspects of the self are represented within the brain. In this paper, we first outline the recent research on the neurocognitive basis of the self and highlight a key distinction between two forms of self-representation. The first is the “bodily” self, which is thought to be the basis of subjective experience and is grounded in the processing of sensorimotor signals. The second is the “conceptual” self, which develops through our interactions of other and is formed of a rich network of associative and semantic information. We then investigate how both the bodily and conceptual self are related to social cognition with an emphasis on how self-representations are involved in the processing and creation of prejudice. We then highlight new research demonstrating that the bodily and conceptual self are both malleable and that this malleability can be harnessed in order to achieve a reduction in social prejudice. In particular, we will outline strong evidence that modulating people’s perceptions of the bodily self can lead to changes in attitudes at the conceptual level. We will highlight a series of studies demonstrating that social attitudes towards various social out-groups (e.g. racial groups) can lead to a reduction in prejudice towards that group. Finally, we seek to place these findings in a broader social context by considering how innovations in virtual reality technology can allow experiences of taking on another’s identity are likely to become both more commonplace and more convincing in the future and the various opportunities and risks associated with using such technology to reduce prejudice

Nonmixing vortex cores in wavy Taylor vortex flow

When the symmetry of axisymmetric Taylor vortex flow is broken, time-periodic wavy vortex flow WVF appears and quite quickly becomes globally chaotic in the Lagrangian sense with increasing Reynolds number. Previously published simulations of WVF suggest that beyond a certain Re, nonmixing vortex cores reappear in the flow and grow in size with further increases in Re. This reappearance occurs well into the inertia-dominated flow regime and coincides with a decrease in axial fluid dispersion and an increase in flow symmetry as measured by certain Eulerian symmetry measures. In this brief paper, we present experimental dye-reaction visualization results from two WVF wave states in the region where vortex cores are predicted numerically. The experimental results show unambiguous visual evidence for the existence of vortex cores and provide visual agreement with the numerical results. They are significant in that experimental evidence for these structures in WVF has not been reported before. The results also suggest that vortex-to-vortex transport occurs via sheetlike structures that are pulled from one vortex to another and become wrapped around the vortex cores before being stretched to the point at which molecular diffusion dominates

Parasitic current generation in Combined Level Set and Volume of Fluid immiscible fluid simulations

The Continuum Surface Force technique is a popular tool used to implement surface tension forces in Eulerian based Computational Fluid Dynamics codes. Under this technique, inaccuracies present in calculating the surface tension force can manifest themselves as `parasitic' currents. We detail a new Combined Level Set and Volume of Fluid implementation of the Continuum Surface Force method. We then develop a correlation for the magnitude of parasitic currents that are generated under this new method, as a function of both the numerical and physical parameters employed in a simulation. A set of numerical experiments validate this correlation and show that, importantly, the magnitude of currents produced by the method decreases as the computational cell size reduced. References J. U. Brackbill, D. B. Kothe, and C. Zemach. A continuum method for modelling surface tension. Journal of Computational Physics, 100:335--354, 1992. Dalton J. E. Harvie, M. R. Davidson, and Murray Rudman. An analysis of parasitic current generation in volume of fluid simulations. Appl. Math Mod., 30(10):1056--1066, 2006. doi:10.1016/j.apm.2005.08.015 D. B. Kothe and R. C. Mjolsness. RIPPLE: A new model for incompressible flows with free surfaces. American Institue of Aeronautics and Astronautics, 30 (11):2694--2700, 1992. Bruno Lafaurie, Carlo Nardone, Ruben Scardovelli, Stephane Zaleski, and Gianluigi Zanetti. Modelling merging and fragmentation in multiphase flows with SURFER. Journal of Computational Physics, 113:134--147, 1994. Murray Rudman. A volume-tracking method for incompressible multifluid flows with large density variations. International Journal for Numerical Methods in Fluids, 28:357--378, 1998. Ruben Scardovelli and Stepahe Zaleski. direct numerical simulation of free-surface and interfacial flow. Annual Review of Fluid Mechanics, 31:567--603, 1999. J. A. Sethian and Peter Smereka. Level set methods for fluid interfaces. Annual Review of Fluid Mechanics, 35:341--372, 2003. doi:10.1146/annurev.fluid.35.101101.161105 Mark Sussman. A second order coupled level set and volume-of-fluid method for computing growth and collapse of vapor bubbles. Journal of Computational Physics, 187:110--136, 2003. doi:10.1016/S0021-9991(03)00087-1 Mark Sussman and Elbridge Gerry Puckett. A coupled level set and volume-of-fluid method for computing 3d and axisymmetric incompressible two-phase flows. Journal of Computational Physics, 162:301--337, 2000. doi:10.1006/jcph.2000.6537 Mark Sussman, Peter Smereka, and Stanley Osher. A level set approach for computing solutions to incompressible two-phase flow. Journal of Computational Physics, 114:146--159, 1994. S. P. van der Pijl, A. Segal, C. Vuik, and P. Wesseling. A mass-conserving level-set method for modelling of multi-phase flows. International Journal for Numerical Methods in Fluids, 47:339--361, 2005. doi:10.1002/fld.81

The role of mixing in gibbsite precipitation

Abstract not available

Mixing, stretching and chaos in wavy Taylor vortex flow

Numerical and experimental investigation of the fluid flow, mixing and stretching in wavy Taylor vortex flow is presented which shows that the effective (chaotic) diffusion coefficient is a function of wave state. This result suggests that a universal relationship between dispersion and Reynolds number cannot be found in this regime of cylindrical Taylor-Couette flow. Fluid retention in the cores of the wavy vortices is also predicted, and fluid trapped in vortex cores is only poorly mixed within the core and plays no role in global mixing except via molecular diffusion. Experimental validation of the existence of vortex core regions in wavy vortex flow is presented for the first time. Mean fluid stretching is also calculated, although a quantitative relationship between stretching and effective axial diffusion is not apparent from the results