prediction of mean and turbulent kinetic energy in rectangular shallow reservoirs

AbstractShallow rectangular reservoirs are common structures in urban hydraulics and river engineering. Despite their simple geometries, complex symmetric and asymmetric flow fields develop in such reservoirs, depending on their expansion ratio and length-to-width ratio. The original contribution of this study is the analysis of the kinetic energy content of the mean flow, based on UVP velocity measurements carried throughout the reservoir in eleven different geometric configurations. A new relationship is derived between the specific mean kinetic energy and the reservoir shape factor. For most considered geometric configurations, leading to four different flow patterns, the experimentally observed flow fields and mean kinetic energy contents are successfully reproduced by an operational numerical model based on the depth-averaged flow equations and a two-length-scale k- turbulence closure. The analysis also highlights the better performance of this depth-averaged k- model compared to an algebraic turbu..

Experimental study of velocity fields in rectangular shallow reservoirs

Velocity fields in rectangular shallow reservoirs with different length-to-width and expansion ratios were investigated in an experimental study, to evaluate the effect of geometry on the flow field. A wide range of combinations of these two non-dimensional geometric parameters were tested at constant hydraulic conditions. Ultrasound velocity profilers were used to measure the horizontal velocity components across the entire reservoir surface, allowing for the visualization of streamlines and of the instantaneous and average velocities. Five different types offlow patterns were identified, depending on the values of the length-to-width ratio and expansion ratio of the reservoir. Asymmetrical flow patterns were found to develop for certain combinations of these geometric parameters despite the perfect reservoir symmetry. A critical comparison of these new experimental results with those of other works is provided

Kepler Monitoring of an L Dwarf II. Clouds With Multiyear Lifetimes

We present Kepler, Spitzer Space Telescope, Gemini-North, MMT, and Kitt Peak observations of the L1 dwarf WISEP J190648.47+401106.8. We find that the Kepler optical light curve is consistent in phase and amplitude over the nearly two years of monitoring with a peak-to-peak amplitude of 1.4%. Spitzer Infrared Array Camera 3.6 µm observations are in phase with Kepler with similar light curve shape and peak-to-peak amplitude 1.1%, but at 4.5 µm, the variability has amplitude < 0.1%. Chromospheric Hα emission is variable but not synced with the stable Kepler light curve. A single dark spot can reproduce the light curve but is not a unique solution. An inhomogeneous cloud deck, specifically a region of thick cloud cover, can explain the multi-wavelength data of this ultracool dwarf and need not be coupled with the asynchronous magnetic emission variations. The long life of the cloud is in contrast with weather changes seen in cooler brown dwarfs on the timescale of hours and days.Astronom

Pseudoaneurysm overlying an osteochondroma: a noteworthy complication

Pseuodaneurysms are an extremely rare complication of osteochondromas. We describe a case of traumatic pseudoaneurysm of the brachial artery presenting as a soft tissue mass in a patient who was treated for an osteochondroma 3 years earlier. This case demonstrates that radiographic follow-up of large osteochondromas is mandatory and that, in patients with soft tissue masses and a history of osteochondroma, pseudoaneurysms should be included in the differential diagnosis

2D versus 3D human induced pluripotent stem cell-derived cultures for neurodegenerative disease modelling

Neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD) and amyotrophic lateral sclerosis (ALS), affect millions of people every year and so far, there are no therapeutic cures available. Even though animal and histological models have been of great aid in understanding disease mechanisms and identifying possible therapeutic strategies, in order to find disease-modifying solutions there is still a critical need for systems that can provide more predictive and physiologically relevant results. One possible avenue is the development of patient-derived models, e.g. by reprogramming patient somatic cells into human induced pluripotent stem cells (hiPSCs), which can then be differentiated into any cell type for modelling. These systems contain key genetic information from the donors, and therefore have enormous potential as tools in the investigation of pathological mechanisms underlying disease phenotype, and progression, as well as in drug testing platforms. hiPSCs have been widely cultured in 2D systems, but in order to mimic human brain complexity, 3D models have been proposed as a more advanced alternative. This review will focus on the use of patient-derived hiPSCs to model AD, PD, HD and ALS. In brief, we will cover the available stem cells, types of 2D and 3D culture systems, existing models for neurodegenerative diseases, obstacles to model these diseases in vitro, and current perspectives in the field

Experimenting with a new calibration method for current meters

The necessity of a simple way to control the reliability of laboratory’s current meters brought to develop a method that allows to calibrate the instruments in their usual working conditions, as it happens, for example, in a river or in a sewer, using an equipment simpler than the traditional method: the current meter is still, hung by a support, and the propeller is put in rotation by flow through totally submerged outflows, exploiting the main characteristic of these outflows, that is a uniform velocity profile on all the cross-section. Since current meter is a local velocity gauger, the influence of current meter’s position, respect to the outflow, on velocity measurements reliability, has been investigated. In fact, the current must be linear to obtain satisfying discharge measurements. Two different kinds of submerged outflows has been analyzed: a flow nozzle and an orifice plate. The problem about the orifice plate is to localize with accuracy where the contracted section A_c is located, that is to say where current is linear, and which is the contraction ratio C_c . Usually, the contracted section is considered to be D_OP /2 far from the outflow. On the contrary, the flow nozzle doesn’t cause a contracted section, because of its well-connected entrance; nevertheless, there is a lot of turbulence around it, because of liquid jet expansion, but, near the outflow, current may be considered linear, assuming, as reference piezometric line, that of the axial flow pattern. To confirm the hypothesis at the basis of the method, that is a uniform velocity distribution on all the cross section, velocity profiles along two directions, horizontal and vertical, have been studied, showing results matching with theory. A calibration method consists in putting into relationship the number of propeller’s rates in a fixed time interval with current velocity, determining instrument’s characteristic calibration curve; in this case, two reference current velocities have been adopted for calibration: the one is the ratio between discharge (indicated by an electromagnetic flow meter) circulating in the system and outflow’s area; the other is obtained by the Torricelli’s formula, measuring the difference between upstream and downstream reservoirs’ levels. In particular, the propellers of two current meters, different in dimension and typtology, have been calibrated by the new method. In the end, since a measurement is complete only if associated to its uncertainty, the uncertainty of measurements carried out has been calculated, in particular about Torricelli’s velocity