Visualización de flujos dominados por vórtices tridimensionales en un tanque de remolque

The present paper describes a series of flow visualization studies, which have been performed in a towing tank and utilize laser ind uced fluorescence as a means of observation. The setup, described herein, has been designed specifically f or visualizing three dimensional vortex dominated flows. Two diff erent projects are being performed currently in this facility. The first one focuses on the development of tip vortices on hydrofoils, and the second on the flow structures behind inclined bodies of revolution. The experimental setup required for both projects, particularly the optical system, is almost identical, and the details are provided in the following section. Brief summaries highlighting some of the results of observations, are provided in the chapters that follow. More detailed information is described by Ward and Katz (1987a,b), and by Francis and Katz (1986).El presente artículo describe una serie de estudios de visualización de flujo, que se han realizado en un tanque de remolque y utilizan fluorescencia inducida por láser como medio de observación. La configuración, descrita en este documento, ha sido diseñada específicamente para visualizar flujos dominados por vórtices tridimensionales. En la actualidad se están realizando dos proyectos diferentes en esta instalación. El primero se centra en el desarrollo de vórtices de borde en perfiles hidrodinámicos, y el segundo en las estructuras del vortice de flujo detrás de cuerpos de revolución inclinados. La configuración experimental requerida para ambos proyectos, en particular el sistema óptico, es casi idéntica y los detalles se proporcionan en la siguiente sección. En los capítulos siguientes se proporcionan breves resúmenes que destacan algunos de los resultados de las observaciones. Ward y Katz (1987a, b) y Francis y Katz (1986) describen información más detallada

Affective picture modulation: Valence, arousal, attention allocation and motivational significance

The present study analyses the modulatory effects of affective pictures in the early posterior negativity (EPN), the late positive potential (LPP) and the human startle response on both the peripheral (eye blink EMG) and central neurophysiological levels (Probe P3), during passive affective pictures viewing. The affective pictures categories were balanced in terms of valence (pleasant; unpleasant) and arousal (high; low). The data shows that EPN may be sensitive to specific stimulus characteristics (affective relevant pictures versus neutral pictures) associated with early stages of attentional processing. In later stages, the heightened attentional resource allocation aswell as themotivated significance of the affective stimuliwas found to elicit enhancedamplitudes of slow wave processes thought to be related to enhanced encoding, namely LPP,. Although pleasant low arousing pictureswere effective in engaging the resources involved in the slowwave processes, the highly arousing affective stimuli (pleasant and unpleasant) were found to produce the largest enhancement of the LPP, suggesting that high arousing stimulimay are associatedwith increasedmotivational significance. Additionally the response to high arousing stimulimay be suggestive of increasedmotivational attention, given the heightened attentional allocation, as expressed in the P3 probe, especially for the pleasant pictures. The hedonic valencemay then serve as amediator of the attentional inhibition to the affective priming, potentiating or inhibiting a shift towards defensive activation, as measured by the startle reflex.Portuguese Foundation for Science and Technology with individual grants (SFRH/BD/41484/2007 and SFRH/BD/64355/2009) and by the Spanish Xunta de Galicia – with FEDER funds – (DOG 233 — Resolution date: 2009 November 18t

Thermodynamic Analysis of Compressed Air Energy Storage (CAES) Reservoirs in Abandoned Mines Using Different Sealing Layers

[EN] Million cubic meters from abandoned mines worldwide could be used as subsurface reservoirs for large scale energy storage systems, such as adiabatic compressed air energy storage (A-CAES). In this paper, analytical and three-dimensional CFD numerical models have been conducted to analyze the thermodynamic performance of the A-CAES reservoirs in abandoned mines during air charging and discharging processes. Unlike other research works, in which the heat transfer coefficient is considered constant during the operation time, in the present investigation a correlation based on both unsteady Reynolds and Rayleigh numbers is employed for the heat transfer coefficient in this type of application. A tunnel with a 35 cm thick concrete lining, 200 m3 of useful volume and typical operating pressures from 5 to 8 MPa were considered. Fiber-reinforced plastic (FRP) and steel were employed as sealing layers in the simulations around the fluid. Finally, the model also considers a 2.5 m thick sandstone rock mass around the concrete lining. The results obtained show significant heat flux between the pressurized air and the sealing layer and between the sealing layer and concrete lining. However, no temperature fluctuation was observed in the rock mass. The air temperature fluctuations are reduced when steel sealing layer is employed. The thermal energy balance through the sealing layer for 30 cycles, considering air mass flow rates of 0.22 kg s−1 (charge) and −0.45 kg s−1 (discharge), reached 1056 and 907 kWh for FRP and steel, respectively. In general, good agreements between analytical and numerical simulations were obtained.S

Concentration, Propagation and Dilution of Toxic Gases in Underground Excavations under Different Ventilation Modes

[EN] The drill-and-blast method is widely used for the excavation of hard rock tunnels. Toxic gases such as carbon monoxide and nitrogen oxides are released immediately after blasting by the detonation of explosives. To provide a safe working environment, the concentration of noxious gases must be reduced below the threshold limit value according to health and safety regulations. In this paper, one-dimensional mathematical models and three-dimensional CFD numerical simulations were conducted to analyze the concentration, propagation and dilution of the blasting fumes under different operating conditions. Forced, exhaust and mixed ventilation modes were compared to determine the safe re-entry times after blasting in a 200 m-long tunnel excavated using the top-heading-and-benching method. Based on the numerical simulations, carbon monoxide was the most critical gas, as it required a longer ventilation time to reduce its concentration below the threshold limit value. The safe re-entry time reached 480 s under the typical forced ventilation mode, but was reduced to 155 s when a mixed ventilation system was used after blasting, reducing the operating costs. The reduction of the re-entry time represents a significant improvement in the excavation cycle. In addition, the results obtained show that 1D models can be used to preliminary analyze the migration of toxic gases. However, to reliably determine the safe re-entry times, 3D numerical models should be developed. Finally, to verify the accuracy of the CFD results, field measurements were carried out in a railway tunnel using gas sensors. In general, good agreements were obtained between the 3D numerical simulations and the measured values.S

Economic feasibility of floating offshore wind farms considering near future wind resources: case study of Iberian Coast and Bay of Biscay

Wind energy resources are subject to changes in climate, so the use of wind energy density projections in the near future is essential to determine the viability and profitability of wind farms at particular locations. Thus, a step forward in determining the economic assessment of floating offshore wind farms was taken by considering current and near-future wind energy resources in assessing the main parameters that determine the economic viability (net present value, internal rate of return, and levelized cost of energy) of wind farms. This study was carried out along the Atlantic coast from Brest to Cape St. Vincent. Results show that the future reduction in wind energy density (2%–6%) mainly affects the net present value (NPV) of the farm and has little influence on the levelized cost of energy (LCOE). This study provides a good estimate of the economic viability of OWFs (Offshore Wind Farms) by taking into account how wind resources can vary due to climate change over the lifetime of the farm.Ministerio de Ciencia e Innovación | Ref. Project PID2019-105386RA-I00Xunta de Galicia | Ref. ED431C 2017/64Fundação para a Ciência e a Tecnologia | Ref. SFRH/BD/114919/2016Fundação para a Ciência e a Tecnologia | Ref. UIDP/50017/2020Fundação para a Ciência e a Tecnologia | Ref. UIDB/50017/202

The emotional movie database (EMDB): a self-report and psychophysiological study

Film clips are an important tool for evoking emotional responses in the laboratory. When compared with other emotionally potent visual stimuli (e.g., pictures), film clips seem to be more effective in eliciting emotions for longer periods of time at both the subjective and physiological levels. The main objective of the present study was to develop a new database of affective film clips without auditory content, based on a dimensional approach to emotional stimuli (valence, arousal and dominance). The study had three different phases: (1) the pre-selection and editing of 52 film clips (2) the self-report rating of these film clips by a sample of 113 participants and (3) psychophysiological assessment [skin conductance level (SCL) and the heart rate (HR)] on 32 volunteers. Film clips from different categories were selected to elicit emotional states from different quadrants of affective space. The results also showed that sustained exposure to the affective film clips resulted in a pattern of a SCL increase and HR deceleration in high arousal conditions (i.e., horror and erotic conditions). The resulting emotional movie database can reliably be used in research requiring the presentation of non-auditory film clips with different ratings of valence, arousal and dominance.Portuguese Foundation for Science and Technology with individual grants (SFRH/BD/41484/2007 and SFRH/BD/64355/2009

Psychophysiological Correlates of Sexually and Non-Sexually Motivated Attention to Film Clips in a Workload Task

Some authors have speculated that the cognitive component (P3) of the Event-Related Potential (ERP) can function as a psychophysiological measure of sexual interest. The aim of this study was to determine if the P3 ERP component in a workload task can be used as a specific and objective measure of sexual motivation by comparing the neurophysiologic response to stimuli of motivational relevance with different levels of valence and arousal. A total of 30 healthy volunteers watched different films clips with erotic, horror, social-positive and social-negative content, while answering an auditory oddball paradigm. Erotic film clips resulted in larger interference when compared to both the social-positive and auditory alone conditions. Horror film clips resulted in the highest levels of interference with smaller P3 amplitudes than erotic and also than social-positive, social-negative and auditory alone condition. No gender differences were found. Both horror and erotic film clips significantly decreased heart rate (HR) when compared to both social-positive and social-negative films. The erotic film clips significantly increased the skin conductance level (SCL) compared to the social-negative films. The horror film clips significantly increased the SCL compared to both social-positive and social-negative films. Both the highly arousing erotic and non-erotic (horror) movies produced the largest decrease in the P3 amplitude, a decrease in the HR and an increase in the SCL. These data support the notion that this workload task is very sensitive to the attentional resources allocated to the film clip, although they do not act as a specific index of sexual interest. Therefore, the use of this methodology seems to be of questionable utility as a specific measure of sexual interest or as an objective measure of the severity of Hypoactive Sexual Desire Disorder

Racial differences in systemic sclerosis disease presentation: a European Scleroderma Trials and Research group study

Objectives. Racial factors play a significant role in SSc. We evaluated differences in SSc presentations between white patients (WP), Asian patients (AP) and black patients (BP) and analysed the effects of geographical locations.Methods. SSc characteristics of patients from the EUSTAR cohort were cross-sectionally compared across racial groups using survival and multiple logistic regression analyses.Results. The study included 9162 WP, 341 AP and 181 BP. AP developed the first non-RP feature faster than WP but slower than BP. AP were less frequently anti-centromere (ACA; odds ratio (OR) = 0.4, P < 0.001) and more frequently anti-topoisomerase-I autoantibodies (ATA) positive (OR = 1.2, P = 0.068), while BP were less likely to be ACA and ATA positive than were WP [OR(ACA) = 0.3, P < 0.001; OR(ATA) = 0.5, P = 0.020]. AP had less often (OR = 0.7, P = 0.06) and BP more often (OR = 2.7, P < 0.001) diffuse skin involvement than had WP.AP and BP were more likely to have pulmonary hypertension [OR(AP) = 2.6, P < 0.001; OR(BP) = 2.7, P = 0.03 vs WP] and a reduced forced vital capacity [OR(AP) = 2.5, P < 0.001; OR(BP) = 2.4, P < 0.004] than were WP. AP more often had an impaired diffusing capacity of the lung than had BP and WP [OR(AP vs BP) = 1.9, P = 0.038; OR(AP vs WP) = 2.4, P < 0.001]. After RP onset, AP and BP had a higher hazard to die than had WP [hazard ratio (HR) (AP) = 1.6, P = 0.011; HR(BP) = 2.1, P < 0.001].Conclusion. Compared with WP, and mostly independent of geographical location, AP have a faster and earlier disease onset with high prevalences of ATA, pulmonary hypertension and forced vital capacity impairment and higher mortality. BP had the fastest disease onset, a high prevalence of diffuse skin involvement and nominally the highest mortality

Reliability of the full equation model (FEQ) for the solution of steady-state and unsteady flows in open channels and rivers

The reliability of the Full EQuation numerical Model (FEQ) to solve the de Saint Venant equations, is evaluated by analyzing the stability and accuracy of the simulation result, when the model is applied to steady state flow and to unsteady flow conditions over the reach or computational element component of an open channel. In the case of steady state flow, the FEQ model results are compared to the exact solution of the gradually varied flow equation, applied to the case of a wide-horizontal rectangular channel. A first order approximation numerical model, a second order approximation numerical model, and the HEC-2 program are also included in the reliability study of the FEQ model to simulate steady state flows. The unsteady flow test is constituted by peaked hydrographs superimposed on the uniform flow conditions. The unsteady flow results from FEQ are compared to the solution of the de Saint Venant equations using the Method of Characteristics. This method has been proved to give stable and accurate results when the time step in the integration is kept very small, that is when the number of subreaches is large. A self comparison analysis for different number of reaches is done to obtain the optimal number of reaches that gives the most stable and accurate results in both models. In each case the comparison is done using graphical and error analysis methods. From these comparisons, the FEQ model shows very stable and accurate results with respect to the other models. For the steady state flow the maximum error found with respect to the exact solution is on the order of 2%. In the case of the unsteady flow this value was 0.05%. The reliability of the model is therefore rather high in simulating both; steady state and unsteady flows in open channels

Transient Simulation of Underground Pumped Storage Hydropower Plants Operating in Pumping Mode

The increasing penetration of variable renewable energies (VRE) in the European electricity mix requires flexible energy storage systems (ESS), such as pumped storage hydropower (PSH). Disused mining voids from deep closed mines may be used as subsurface reservoirs of underground pumped-storage hydropower (UPSH) plants. Unlike conventional PSH plants, the air pressure in UPSH plants is variable and it differs from the atmospheric conditions. In this paper, the hydraulic transient process of an UPSH plant operating in pumping mode was investigated and a preliminary thermodynamic analysis of the closed surge tank was carried out. Analytical and CFD three-dimensional numerical simulations based on the volume of fluid (VOF) model with two-phase flow have been performed for analyzing the transient process. In the transient simulation, air and water are considered as ideal gas and compressible liquid, respectively. Different guide vanes closing schemes have been simulated. The obtained results show that the dimensioning of underground reservoir, surge tank, and air ducts is essential for ensuring the hydraulic performance and optimizing the operation of UPSH plants. The static pressure in the air duct, surge tank and lower reservoir reaches −1.6, 112.8 and −4 kPa, respectively, while a heat flux of −80 W was obtained through the surge tank walls