Modeling Turbulent Flow in Stirred Tanks with CFD: The Influence of the Modeling Approach, Turbulence Model and Numerical Scheme

Single phase turbulent flow in a tank stirred by a down- and an up-pumping pitched blade turbine has been simulated using CFD. The effect of the modeling approach, discretization scheme and turbulence model on mean velocities, turbulent kinetic energy and global quantities, such as the power and circulation numbers, has been investigated. The results have been validated by LDV data. The stationary and time-dependent modeling approaches were found to have little effect on the turbulent flow, however the choice of the numerical scheme was found to be important, especially for the predicted turbulent kinetic energy. A first order method was found to highly underestimate LDV data compared with higher order methods. The type of the turbulence model was limited to the k-e and RNG models due to convergence difficulties encountered with a Reynolds Stress Model (RSM) and there was found to be little effect of these models on the mean flow and turbulent kinetic energy. This latter quantity was found to be largely under predicted in the discharge region of the down-pumping impeller in comparison with LDV data. Better agreement was found for the up-pumping pitched blade turbine. Estimated power numbers were found generally to be in good agreement for the down- and up-pumping data. However, the circulation number tended to be over predicted by about 30% and 40% for the down- and uppumping agitators, respectively

Determining Energy Balance in the Flaring Chromosphere from Oxygen V Line Ratios

The impulsive phase of solar flares is a time of rapid energy deposition and heating in the lower solar atmosphere, leading to changes in the temperature and density structure of the region. We use an O V density diagnostic formed of the 192 to 248 line ratio, provided by Hinode EIS, to determine the density of flare footpoint plasma, at O V formation temperatures of 250,000 K, giving a constraint on the properties of the heated transition region. Hinode EIS rasters from 2 small flare events in December 2007 were used. Raster images were co-aligned to identify and establish the footpoint pixels, multiple-component Gaussian line fitting of the spectra was carried out to isolate the diagnostic pair, and the density was calculated for several footpoint areas. The assumptions of equilibrium ionization and optically thin radiation for the O V lines were found to be acceptable. Properties of the electron distribution, for one event, were deduced from earlier RHESSI hard X-ray observations and used to calculate the plasma heating rate, delivered by an electron beam adopting collisional thick-target assumptions, for 2 model atmospheres. Electron number densities of at least log n = 12.3 cm-3 were measured during the flare impulsive phase, far higher than previously expected. For one footpoint, the radiative loss rate for this plasma was found to exceed that which can be delivered by an electron beam implied by the RHESSI data. However, when assuming a completely ionised target atmosphere the heating rate exceeded the losses. A chromospheric thickness of 70-700 km was found to be required to balance a conductive input to the O V-emitting region with radiative losses. The analysis shows that for heating by collisional electrons, it is difficult, or impossible to raise the temperature of the chromosphere to explain the observed densities without assuming a completely ionised atmosphere.Comment: Accepted to A&A 14th September 201

Sport psychologists’ experiences of organizational stressors

This study extends stress research by exploring sport psychologists’ experiences of organizational stressors. Twelve accredited sport psychologists (6 academics and 6 practitioners) were interviewed regarding their experiences of organizational stress within their jobs. Content analysis involved categorizing the demands associated primarily and directly with their occupation under one of the following general dimensions: factors intrinsic to sport psychology, roles in the organization, sport relationships and interpersonal demands, career and performance development issues, and organizational structure and climate of the profession. A frequency analysis revealed that academics (ΣAOS = 201) experienced more organizational stressors than practitioners (ΣPOS = 168). These findings indicate that sport psychologists experience a wide variety of organizational stressors across different roles, some of which parallel those found previously in other professions. The practical implications for the management of stress for sport psychologists are discussed

Asthma control and management in 8,000 European patients : the REcognise Asthma and LInk to Symptoms and Experience (REALISE) survey

We thank Dr Peter Haidl (Schmallenberg, Germany) and Professor Chantal Raherison-Semjen (Bordeaux, France) for their advice and input on the survey questions. We are also grateful to Weber Shandwick (London, UK) for assistance in developing and running the survey, Incite Marketing Planning Ltd (London, UK) for support in the development of the questionnaire and analysing the results, and Dr Mark Rolfe and Dr Andreas Leidenroth (Oxford PharmaGenesis, Oxford, UK) for medical writing support.Peer reviewedPublisher PD

Advanced Spacecraft Designs in Support of Human Missions to Earth's Neighborhood

NASA's strategic planning for technology investment draws on engineering studies of potential future missions. A number of hypothetical mission architectures have been studied. A recent study completed by The NASA/JSC Advanced Design Team addresses one such possible architecture strategy for missions to the moon. This conceptual study presents an overview of each of the spacecraft elements that would enable such missions. These elements include an orbiting lunar outpost at lunar L1 called the Gateway, a lunar transfer vehicle (LTV) which ferries a crew of four from the ISS to the Gateway, a lunar lander which ferries the crew from the Gateway to the lunar surface, and a one-way lunar habitat lander capable of supporting the crew for 30 days. Other supporting elements of this architecture discussed below include the LTV kickstage, a solar-electric propulsion (SEP) stage, and a logistics lander capable of re-supplying the 30-day habitat lander and bringing other payloads totaling 10.3 mt in support of surface mission activities. Launch vehicle infrastructure to low-earth orbit includes the Space Shuttle, which brings up the LTV and crew, and the Delta-IV Heavy expendable launch vehicle which launches the landers, kickstage, and SEP

Human Lunar Destiny: Past, Present, and Future

This paper offers conceptual strategy and rationale for returning astronauts to the moon. NASA's historic Apollo program enabled humans to make the first expeditionary voyages to the moon and to gather and return samples back to the earth for further study. To continue exploration of the moon within the next ten to fifteen years, one possible mission concept for returning astronauts using existing launch vehicle infrastructure is presented. During these early lunar missions, expeditionary trips are made to geographical destinations and permanent outposts are established at the lunar south pole. As these missions continue, mining operations begin in an effort to learn how to live off the land. Over time, a burgeoning economy based on mining and scientific activity emerges with the formation of more accommodating settlements and surface infrastructure assets. As lunar activity advances, surface infrastructure assets grow and become more complex, lunar settlements and outposts are established across the globe, travel to and from the moon becomes common place, and commerce between earth and the moon develops and flourishes. Colonization and development of the moon is completed with the construction of underground cities and the establishment of a full range of political, religious, educational, and recreational institutions with a diverse population from all nations of the world. Finally, rationale for diversifying concentrations of humanity throughout earth's neighborhood and the greater solar system is presented

Impulsive Heating of Solar Flare Ribbons Above 10 MK

The chromospheric response to the input of flare energy is marked by extended extreme ultraviolet (EUV) ribbons and hard X-ray (HXR) footpoints. These are usually explained as the result of heating and bremsstrahlung emission from accelerated electrons colliding in the dense chromospheric plasma. We present evidence of impulsive heating of flare ribbons above 10 MK in a two-ribbon flare. We analyse the impulsive phase of SOL2013-11-09T06:38, a C2.6 class event using data from Atmospheric Imaging Assembly (AIA) on board of Solar Dynamics Observatory (SDO) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) to derive the temperature, emission measure and differential emission measure of the flaring regions and investigate the evolution of the plasma in the flaring ribbons. The ribbons were visible at all SDO/AIA EUV/UV wavelengths, in particular, at 94 and 131 \AA\ filters, sensitive to temperatures of 8 MK and 12 MK. Time evolution of the emission measure of the plasma above 10 MK at the ribbons has a peak near the HXR peak time. The presence of hot plasma in the lower atmosphere is further confirmed by RHESSI imaging spectroscopy analysis, which shows resolved sources at 11-13 MK associated with at least one ribbon. We found that collisional beam heating can only marginally explain the necessary power to heat the 10 MK plasma at the ribbons.Comment: 21 pages, 15 figure

McNeal, Dale, Oral history interview

McNeal, Dale (1969-2002) Professor of Biology Topics include: Changes in biological sciences curriculum, general education programs, advising pre-health professional majors, role of faculty in shared governance and committees, role ofadministrators & relationships with faculty, makeup of student body.https://scholarlycommons.pacific.edu/esohc/1123/thumbnail.jp