Numerical simulation of an air-core vortex at a hydraulic intake using OpenFOAM

A vortex is a ubiquitous everyday phenomenon that is observed in nature and it is formed due to the rotational motion of fluid around an axis perpendicular to the free surface. Free surface vortices are a common unwanted occurrence at hydraulic intakes which can cause serious detrimental impacts on mechanical devices such as turbines and pumps. In this paper, an experimentally observed air-core vortex is numerically simulated using the OpenFOAM LTSInterFoam solver. The LTSInterFoam solver has hitherto been mainly used for hydrodynamic studies relating to ship manoeuvrability by researchers. This solver uses a local time stepping approach to speed up convergence towards steady state conditions thus overcoming some of the challenges associated with the use of the conventional interFoam solver for the simulation of free surface vortices. The Shear Stress Transport (SST) k−ω Model was used for the simulation. There was generally good agreement when results from the study were compared with other vortex-related analytical models and experimental data. Overall, the study concludes that the OpenFOAM LTSInterFoam solver is capable of simulating free surface vortices at hydraulic intakes. However, being a steady state solver, the solver cannot account for the transient process involved in the evolution of free surface vortices

Free surface vortices at hydropower intakes: – A state-of-the-art review

This is the final version. Available on open access from Elsevier via the DOI in this recordFor years, the study of free surface vortices at hydropower plant intakes has been a topical and intriguing subject among engineers and researchers. This subject will continue to attract attention especially as the world strives to meet the ever-increasing demand for energy. Despite the numerous benefits associated with hydropower, the sustainability of some hydropower plants is being threatened due to low inflows often associated with climate change. Free surface vortices associated with low water levels or submergence at plant intakes can have very detrimental consequences on the operation of hydropower plants if not addressed. Notwithstanding this, free surface vortex flows have also been found to be very relevant in emerging technologies such as the water vortex hydropower plant system. This paper, therefore, presents a state-of-the-art review of the subject including summarised historical findings, but with an emphasis on current developments, findings and research gaps to guide practitioners and researchers. In response to the research gaps identified, the authors make a number of recommendations for further studies which include establishing relationships between free surface vortices formation and turbine efficiency, development of more accurate models for critical submergence and free surface vortices, assessment of free surface vortices at multiple and multi-level intakes, establishing the relationship between free surface vortices and sediment transport at intakes, application of Computational Fluid Dynamics (CFD) shape optimization tools for intake and anti-vortex device optimisation, as well as the continuing development of CFD tools to simulate air-entrained vortices at hydropower intakes

Impact of RTS,S/AS02A and RTS,S/AS01B on Genotypes of P. falciparum in Adults Participating in a Malaria Vaccine Clinical Trial

Objective:RTS,S, a candidate vaccine for malaria, is a recombinant protein expressed in yeast containing part of the circumsporozoite protein (CSP) sequence of 3D7 strain of Plasmodium falciparum linked to the hepatitis B surface antigen in a hybrid protein. The RTS,S antigen is formulated with GSK Biologicals\u27 proprietary Adjuvant Systems AS02A or AS01B. A recent trial of the RTS,S/AS02A and RTS,S/AS01B vaccines evaluated safety, immunogenicity and impact on the development of parasitemia of the two formulations. Parasite isolates from this study were used to determine the molecular impact of RTS,S/AS02A and RTS,S/AS01B on the multiplicity of infection (MOI) and the csp allelic characteristics of subsequent parasitemias.Design:The distribution of csp sequences and the MOI of the infecting strains were examined at baseline and in break-through infections from vaccinated individuals and from those receiving a non-malarial vaccine.Setting:The study was conducted in Kombewa District, western Kenya.Participants:Semi-immune adults from the three study arms provided isolates at baseline and during break-through infections.Outcome:Parasite isolates used for determining MOI and divergence of csp T cell–epitopes were 191 at baseline and 87 from break-through infections.Results:Grouping recipients of RTS,S/AS01A and RTS,S/AS02B together, vaccine recipients identified as parasite-positive by microscopy contained significantly fewer parasite genotypes than recipients of the rabies vaccine comparator (median in pooled RTS,S groups: 3 versus 4 in controls, P = 0.0313). When analyzed separately, parasitaemic individuals in the RTS,S/AS01B group, but not the RTS,S/AS02A group, were found to have significantly fewer genotypes than the comparator group. Two individual amino acids found in the vaccine construct (Q339 in Th2R and D371 in Th3R) were observed to differ in incidence between vaccine and comparator groups but in different directions; parasites harboring Q339 were less common among pooled RTS,S/AS vaccine recipients than among recipients of rabies vaccine, whereas parasites with D371 were more common among the RTS,S/AS groups.Conclusions:It is concluded that both RTS,S/AS vaccines reduce multiplicity of infection. Our results do not support the hypothesis that RTS,S/AS vaccines elicit preferential effects against pfcsp alleles with sequence similarity to the 3D7 pfcsp sequence employed in the vaccine construct

The molecular and cellular signatures of the mouse eminentia thalami support its role as a signalling centre in the developing forebrain

The mammalian eminentia thalami (EmT) (or thalamic eminence) is an embryonic forebrain structure of unknown function. Here, we examined the molecular and cellular properties of the mouse EmT. We first studied mRNA expression of signalling molecules and found that the EmT is a structure, rich in expression of secreted factors, with Wnts being the most abundantly detected. We then examined whether EmT tissue could induce cell fate changes when grafted ectopically. For this, we transplanted EmT tissue from a tau-GFP mouse to the ventral telencephalon of a wild type host, a telencephalic region where Wnt signalling is not normally active but which we showed in culture experiments is competent to respond to Wnts. We observed that the EmT was able to induce in adjacent ventral telencephalic cells ectopic expression of Lef1, a transcriptional activator and a target gene of the Wnt/β-catenin pathway. These Lef1-positive;GFP-negative cells expressed the telencephalic marker Foxg1 but not Ascl1, which is normally expressed by ventral telencephalic cells. These results suggest that the EmT has the capacity to activate Wnt/β-catenin signalling in the ventral telencephalon and to suppress ventral telencephalic gene expression. Altogether, our data support a role of the EmT as a signalling centre in the developing mouse forebrain. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00429-015-1127-3) contains supplementary material, which is available to authorized users