Dynamic stall is a fluid dynamics phenomenon experienced by airfoils undergoing a rapid variation in their operating conditions, such as in the presence of pitching or plunging motions, when the ...effective angle of attack exceeds the static stall angle. The flow field near the airfoil is characterized by the presence of a strong clockwise vortex originating near the leading edge, which is convected downstream along the suction side, generating a low-pressure region and a continuous rise in lift. A controlled form of dynamic stall is involved in the flight mechanism of some natural flapping-wing flyers, and this is currently a matter of interest for the design of biomimetic micro aerial vehicles. Dynamic stall is also responsible for limitations in helicopters' forward-flight velocity, it can lead to flutter in fixed-wing aircraft and vibration-induced damage in wind turbine blades. In this work, 2D URANS and LES numerical simulations have been carried out for incompressible dynamic stall flow cases over an SD7003 airfoil at a Reynolds number of 6⋅104 and at a reduced frequency of 0.25, with the aim of assessing the validity and the role of low fidelity simulations in dynamic stall prediction, at operating conditions relevant for micro air vehicles. Simulations have been conducted both in the case of periodic pitching and plunging, in order to investigate similarities and differences in the resulting flow fields and aerodynamic coefficients. The effect of the reduced frequency on the agreement between 2D URANS and LES has also been evaluated for an airfoil under periodic plunging.
Lupus nephritis (LN) is a disease marked by autoantibodies against complement components. Autoantibodies against negative complement regulator factor H (anti-FH) are prevalent in aHUS, are associated ...with deletion of factor H-related protein 1 (FHR1) gene, and have overt functional consequences. They are also observed in C3 glomerulopathies. The frequency and relevance of anti-FH in LN are poorly studied.
The aim of our investigation was to screen for the presence of anti-FH and FHR1 gene deletion in a cohort of LN patients and to evaluate their association with LN activity.
ELISA test and Western blot for detection of anti-FH and FHR1 deletion were used, respectively. Patients’ clinical and laboratory parameters regarding anti-FH role were processed by statistical analysis.
Anti-FH were found at low level in a small number of LN patients – 11.7% (7/60) and were not associated with deletion of FHR1. Anti-FH did not correlate with ANA titers, anti-dsDNA, C3/C4 hypocomplementemia, eGFR, proteinuria, or active urinary sediment in LN patients. A weak correlation was found between anti-FH and anti-C3 levels. Anti-FH were linked with endocapillary proliferation and histological activity index. Four anti-FH positive patients had severe to moderate LN as per the BILAG renal score.
Anti-FH autoantibodies are an accessory finding in LN and are more likely to manifest during the active phase of the disease. Due to their low frequency and plasma levels, they do not seem suitable for routine laboratory investigation in patients with LN.
La nefritis lúpica (NL) es una enfermedad caracterizada por autoanticuerpos contra componentes del complemento. Los autoanticuerpos contra el factor H regulador negativo del complemento (anti-FH) son prevalentes en el síndrome urémico hemolítico atípico, están asociados con la eliminación del gen de la proteína 1 relacionada con el factor H (FHR1) y tienen consecuencias funcionales evidentes. También se observan en las glomerulopatías C3. La frecuencia y la relevancia de los anticuerpos anti-FH en NL son poco conocidas.
El objetivo de nuestra investigación fue detectar la presencia de anti-FH y deleción del gen FHR1 en una cohorte de pacientes con NL y evaluar su asociación con la actividad de la NL.
Se usaron pruebas ELISA y Western blot para detectar autoanticuerpos anti-FH y la deleción de FHR1. Se evaluaron los parámetros clínicos y de laboratorio de los pacientes en relación con el anti-FH.
Se encontraron anti-FH en niveles bajos en un pequeño número de pacientes con NL: 11,7% (7/60), sin asociación con la eliminación de FHR1. Anti-FH no se correlacionó con ANA, anti-ADNbc, hipocomplementemia C3/C4, eGFR, proteinuria o sedimento urinario activo en pacientes con NL. Se encontró una correlación débil entre los niveles de anti-FH y anti-C3. Los anti-FH estaban asociados con la proliferación endocapilar y el índice de actividad histológica. Cuatro pacientes con anti-FH tenían NL severa/moderada según BILAG.
Los anti-FH son un hallazgo secundario en la NL y es más probable que se manifiesten durante la fase activa de la enfermedad. Por su baja frecuencia y sus niveles plasmáticos, no son adecuados para investigación de laboratorio de rutina en pacientes con NL.
Outdoor urban ventilation in a real complex urban area is investigated by introducing a new ventilation indicator – the “air delay”. Computational Fluid Dynamics (CFD) simulations are performed using ...the 3D steady Reynolds-Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) approaches. The up-to-date literature shows the lack of detailed evaluations of the two approaches for real compact urban areas. This study further presents a systematic evaluation of steady RANS and LES for the assessment of the ventilation conditions in a dense district in Nicosia, Cyprus. The ventilation conditions within the urban area are investigated by calculating the distribution of the age of air. To better assess the outdoor ventilation, a new indicator, the “air delay” is introduced as the difference between the local mean age of air at an urban area and that in an empty domain with the same computational settings, allowing the comparison of the results in different parts of the domain, without impact of the boundary conditions. CFD results are validated using wind-tunnel measurements of mean wind speed and turbulence intensity performed for the same urban area. The results show that LES can accurately predict the mean wind speed and turbulence intensity with the average deviations of about 6% and 14%, respectively, from the wind-tunnel measurements while for the steady RANS, these are 8% and 31%, respectively. The steady RANS simulations overestimate the local mean air delay. The deviation between the two approaches is 52% at pedestrian level (2 m).
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•Wind tunnel and CFD are used to evaluate ventilation conditions in real urban areas.•RANS and LES are systematically evaluated to predict ventilation conditions.•New indicator “air delay” is introduced to better assess outdoor ventilation.•Steady RANS overestimates the local mean air delay in urban areas.•Average deviation steady RANS-LES in local mean air delay is 52% at pedestrian level.
Three-dimensional Large Eddy Simulation (LES) is performed to numerically investigate the implication of air throttling on the combustion performance of ethylene fueled dual-cavity scramjet ...combustor. The augmentation of combustion performance with the conjunction of throttling and dual cavity being established, the effects of L/D ratio and interspacing distance between the cavities is discussed. Our results indicate that combustion efficiency is enhanced owing to the pre-combustion shock train generated because of the introduction of air throttling for different configurations of cavity. Further, the combination of air-throttling with dual cavity improves combustion performance in comparison with dual cavity without air throttling. Also, dual cavity with L/D = 7 and spacing S = 12 mm displays intense and larger recirculation zones in comparison with other configurations being considered. It is found that for dual cavity with L/D = 7 and S = 12 mm, shorter mixing length and higher penetration height is attained.
•Air-throttling enhances combustion performance in cavity-strut-based scramjet.•Interplay of air-throttling and dual cavity on combustion performance is discussed.•Onset of air throttling intensifies recirculation zone enhancing combustion.•Effect of L/D ratio and spacing of dual cavity with air-throttling is studied.
The choice of proper turbulence models in computational fluid dynamics is still a challenging issue for accurately predicting outdoor microclimate and thermal comfort conditions in urban planning. ...This study compared the performances of the Steady Reynolds Averaged Navier–Stokes (SRANS) RNG k-ε, Large Eddy Simulation (LES) and Detached Eddy Simulation (DES) modeling approaches in simulating the wind flow around an isolated building (with a 1:1:2 shape). The effects of the computational parameters were analyzed, including the grid resolution for all cases, and the discretization time step (Δt) and non-dimensional sampling time (t*) for the LES and DES cases. The results of the LES and DES simulations were affected by the gradual decrease in Δt and increase in t* until the two parameters reached 0.005 s and 288, respectively. The mean velocity fields on the windward side of the building predicted by the three models were in good agreement with the wind tunnel results. However, the results of the LES and DES cases were in better agreement with the experimental results for the leeward and lateral regions in both vertical and horizontal planes. The DDES (Delayed Detached Eddy Simulation) and LES models predicted similar results in the wake region, but the DDES has a lower overall mesh requirement. It is encouraging that the DDES model provides not only the mean flow field, but also the instantaneous wind characteristics, which can be useful for more accurate analysis of outdoor wind and thermal comfort.
•Performances of SRANS, LES and DES modeling approaches are compared in simulating airflow around a building.•Effects of discretization time step and sampling time are analyzed.•DES can produce results similar as LES with lower mesh numbers and lower computing time.•Instantaneous wind flow features around a building can be obtained from DES.•DES is demonstrated in saving computational time and hardware requirements.
The notion of seascape is seldom referred to in the scientific literature. Establishing links with the seascape in the same manner as the landscape has been approached in terrestrial spaces is not ...self-evident, as the usual reference points are disrupted. This work proposes to determine a number of milestones by studying the relationship established with the seascape by the practice of sailing. The article addresses the specific challenges posed by the seascape. But above all, it highlights aspects such as the reference points relating to this biophysical environment which make it possible for one to situate and orient oneself, the necessary adaptations for life at sea, and the representations conveyed by the practice of sailing.
Circuits of Visibility explores transnational media environments as pathways to understand the gendered constructions and contradictions that underwrite globalization. Tracking the ways in which ...gendered subjects are produced and defined in transnationally networked, media saturated environments, Circuits of Visibility presents sixteen essays that collectively advance a discussion about sexual politics, media, technology, and globalization. Covering the internet, television, books, telecommunications, newspapers, and activist media work, the volume directs focused attention to the ways in which gender and sexuality issues are constructed and mobilized across the globe. Contributors' essays span diverse global sites from Myanmar and Morocco to the Balkans, France, U.S., and China, and cover an extensive terrain from consumption, aesthetics and whiteness to masculinity, transnational labor, and cultural citizenship. Circuits of Visibility initiates a necessary conversation and political critique about the mediated global terrain on which sexuality is defined, performed, regulated, made visible, and experienced.
Documenting Gendered Violence explores the intersections of documentary and gendered violence. Several contributors investigate representations through grounded textual analyses of key films and ...videos, including Sex Crimes Unit (2011) and The Invisible War (2012),and other documentary texts including Youtube, photographs, and theater. Other chapters use analysis and interviews to explore how gender violence issues impact production and how these documentaries become part of collaborations and awareness movements.
Current computational trends related to turbulent gas-liquid flow are discussed, together with the developments and open challenges needed to bring the discipline to a mature stage. The contribution ...presents the possibilities offered today by turbulent scale-resolving strategies (Large-Eddy Simulation, LES) to treat complex, multiphase flow topology in system components, and transcending more conventional kinetic energy dissipation-based models combined with phase-average approaches. The LES approach of turbulent gas-liquid flows introduced here under its sub-variants LESS and LEIS (Large-Eddy & Structures Simulation and Large-Eddy & Interface Simulation) is based on unifying the phase averaging concept and the turbulent-scale filtering operations into one single process. The paper is written in the spirit of a review, albeit it provides enough derivation details including the connection between the supergrid (resolved) and subgrid (unresolved) physics. A particular attention is paid here to the various attempts to model the underlying subgrid physics, including DNS-based model upscaling. A brief review of LEIS and LESS applications to phase-change heat transfer problems is provided, too. While the LESS variant based on the filtered multi-fluid equations is best suited for a range of problems in which one of the phases is dispersed in the other, LEIS provides further accuracy by directly predicting interface dynamics and turbulence motions down to the grid level. The paper addresses also the required developments for more complex multi-scale, multi-fluid flow problems, including a new approach termed as ARM, short for All-Regime Multiphase flow model.
In the present paper, Large Eddy Simulations combined with the Zwart-Gerber-Belamri cavitation model are conducted to study the flow characteristics in a tip-leakage flow. A reasonable agreement is ...obtained between the numerical and experimental data. With the numerical results, the influence of cavitation in a tip-leakage flow on the gross features of tip-leakage vortex (TLV) and tip-separation vortex (TSV), the behavior of tip-leakage jet, the time-averaged vorticity field and turbulent kinetic energy (TKE) distributions are discussed in detailed. Our results demonstrate that more complex induced vortexes are observed in the non-cavitation case when compared with the cavitation case. Moreover, the results indicate that cavitation promotes the fusion of TLV and TSV. The narrower passageway in the gap when cavitation occurs increases the strength of tip-leakage jet, which leaves significant influence on local vorticity and turbulent kinetic energy. Cavitation trends to suppress the production of spanwise and pitchwise vorticity and promotes the TKE production. Further analysis shows that the spanwise and pitchwise flow patterns are mainly responsible for the TKE production. The fluctuations of v and w velocity and the corresponding spanwise and pitchwise velocity gradient components need to be controlled if a decrease in the viscous losses is desired.
•The tip-leakage cavitating flow is simulated by LES.•Evolution and dynamic behavior of TLV and TSV are identified and discussed.•The mechanism of cavitation on TKE is clarified.
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