Numerical ABL Wind Tunnel Simulations with Direct Modeling of Roughness Elements through Immersed Boundary Condition Method

Reproduction of atmospheric boundary layer wind tunnel experiments by numerical simulation is achieved in this work by directly modeling with immersed boundary method the geometrical elements placed in the wind tunnel's floor to induce the desired characteristics to the boundary layer.The wind tunnel has a cross section of 2.2 m x 2.25 m, with an inlet region 14 m long and a working region 2 m long. Boundary layer development is shaped up with a series of cubical elements, 3 cm in side, placed in a regular staggered arrangement with a 15 cm spacement. Vortex induction, Standen spires type elements, of 13,4 cm height, and a wall of 31.5 cm height are placed at the inlet. This arrangement is used to reproduce a representative urban site boundary layer (figure 1).The numerical model is implemented on the basis of the open source modelcaffa3d.MBRi [Usera et al 2008], which uses a finite volume method over block structured grids, coupled with various LES approaches for turbulence modeling and parallelization through domain decomposition with MPI [Mendina et al 2013]. Simulations were setup with approximately 2 million cells per block, with a 26 block arrangement. The computational grid is horizontally uniform with a resolution of 1.04 cm x 1.04 cm and nonuniform in vertical direction with the grid points concentrated near the floor . The grid spacing is geometrically stretched away from the floor with a minimum value of 1mm. The time step is 0.1 second and the computation is distributed in 26 cores on the Cluster-FING infraestructure [www.fing.edu.uy/cluster]. The Immersed boundary method approach followed the work of [Liao et al 2009]. Numerical simulation results are compared to wind tunnel measurements for the mean velocity profiles (figure 2), rms profiles and spectrums, providing good overall agreement. We conclude that the Immersed Boundary Condition method is a promising approach to numerically reproduce ABL Boundary Layer development methods used in physical modeling.Agencia Nacional de Investigación e Innovació

redesign and manufacturing of a metal towing hook via laser additive manufacturing with powder bed

Abstract An approach to redesign and manufacture a metal towing hook via Selective Laser Melting is discussed. Some reference criteria and general guidelines are considered step-by-step to concurrently address lightening, manufacturability and job planning. Grounds are given for the application of Additive Manufacturing for complex components to the purpose of material saving and increased safety factor

Clinica medica ú Observaciones selectas recogidas en el Hospital de la Caridad (Clinica de M. Lerminier)

Contiene: T. I-II. Enfermedades del pecho -- T. III-IV. Enfermedades del abdomen -- T. V. Enfermedades del encéfal

Indications and Outcomes of Osteoporosis and Bone Modulation Therapies

Osteoporosis is a disorder of bone strength that leads to an increased risk of fractures. It is most commonly seen in patients aged 50 or older, although it can sometimes occur at a younger age if there are other comorbidities present. The most common cause of osteoporosis by far is menopause, although it also occurs in men, usually with higher morbidity rates than those seen in women. There are many treatment options available, such as anabolics and antiresorptives, with many more currently being developed. However, osteoporosis remains grossly unrecognized and untreated, resulting in a significant strain on the American economy

Antiresorptive Therapies for Osteoporosis

Osteoporosis is a disease of low bone density, translating to increased fragility and risk for fracture. It is a significant public health problem that is widely undertreated, despite the many options of treatment available. Among these, the most effective are the antiresorptive medications, such as bisphosphonates. There is an abundance of evidence about the efficacy and safety profile of these medications. However, there is mounting evidence that, after 10 years on treatment with a bisphosphonate, patients are at a higher risk of developing some of the serious side effects of atypical femur fractures and osteonecrosis of the jaw

The relationship of Physical performance and Osteoporosis prevention with vitamin D in older African Americans (PODA)

© 2017 Elsevier Inc. Rationale Vitamin D deficiency is associated with bone loss, poor muscle strength, falls and fracture. This information in older African Americans (AAs) is sparse. Objective The study of the relationship of Physical performance, Osteoporosis prevention with vitamin D in older African Americans (PODA) is a randomized, double-blind, placebo-controlled 3-year trial examining the effect of vitamin D on bone loss and physical performance in older AA women. Methods 260 healthy AA women aged \u3e 60 years were assigned to receive placebo or vitamin D3. Initial vitamin D3dose was determined by the baseline serum 25OHD level, and adjusted further to maintain serum 25OHD between 30 and 69 ng/ml. Subjects with baseline 25OHD levels ≤ 8 ng/ml or ≥ 26 ng/ml were excluded. Objective measures of neuromuscular strength [Short Physical Performance Battery (SPPB), grip strength and 6-minute walking distance (6MWD)] and bone mineral density (BMD) were obtained. Results SPPB gait speed, grip strength and 6MWD showed a significant positive correlation with free 25OHD. 1 pg/ml increase in free 25OHD predicted a 32% increase in the odds of having higher gait speed and a 1.42 lb. increase in grip strength. No significant differences in BMI, BMD, muscle mass, grip strength, serum total 25OHD and free 25OHD were observed between groups. None of the measures of physical performance showed an association with baseline serum 25OHD. Conclusions This is the first study to show an association between free 25OHD and physical performance. These findings indicate a positive relationship of free 25OHD with gait speed and grip strength in older AA women. Further studies are needed to understand the role of free 25OHD

Instabilities developed in stratified flows over pronounced obstacles

In the present work we study numerical and experimentally the flow of a two-layer stratified fluid over a topographic obstacle. The problem reflects a wide number of oceanographic and meteorological situations, where the stratification plays an important role. We identify the different instabilities developed by studying the pycnocline deformation due to a pronounced obstacle. The numerical simulations were made using the model caffa3D.MB which works with a numerical model of Navier-Stokes equations with finite volume elements in curvilinear meshes. The experimental results are contrasted with numerical simulations. Linear stability analysis predictions are checked with particle image velocimetry (PIV) measurements.</p

Two-layer stratified flows over pronounced obstacles at low-to-intermediate Froude numbers

Two-layer stratified flows over abrupt topographic obstacles, simulating relevant situations in oceanographic problems, are investigated numerically and experimentally in a simplified two-dimensional situation. Experimental results and numerical simulations are presented at low-to-intermediate Froude numbers for two different obstacles: one semicylindrical and the other prismatic. In both cases, four different flow regimes downstream of the obstacles are found: (I) subcritical flow, (II) internal hydraulic jump, (III) Kelvin-Helmholtz instability at the interface, and (IV) shedding of billows. The critical values of the Froude number for the transition between different regimes depend strongly on the shape of the obstacle. In regime (III), we show that the characteristics of the lee wave that appears past the obstacle can be explained with a theoretical stability analysis. Almost independence of the vortex shedding frequency with upstream velocity is observed and explained.</p