Numerical simulation of flow interaction between stationary and downstream elastically mounted cylinders at low reynolds numbers

The vortex-induced vibration phenomenon can occur as a result of the action of wind on bridges, slender buildings, chimneys and energy transmission cables besides the action of water flow on pipelines and risers, among others. Despite the simplicity of the geometry of the circular cylinders, the uniform flow around them is very complex and important, since it may induce unsteady forces on structures associated with vortex shedding. This paper describes the study of two circular cylinders in tandem arrangement subject to bidimensional uniform laminar flows at low Reynolds numbers. The numerical model Ifeinco, which is based on the finite element method and uses a partitioned scheme that considers twoway interaction of fluid flow and structure, has been employed in the analysis. The fluid flow model uses a semi-implicit two-step Taylor-Galerkin method to discretize the Navier-Stokes equations whereas the arbitrary Lagrangean-Eulerian formulation to follow the cylinder motion. This movement has been described by the one DOF dynamic equation for the transverse direction discretized in time by the implicit Newmark method. Both cylinders are immersed in water and the downstream one is elastically mounted in transversal direction. Firstly, stationary cylinders in tandem arrangement for Re = 100 are analysed for L/D from 1.5 to 6.0. Results of lift and drag coefficients and Strouhal number are compared with other numerical results and good agreement is found. These analyses show that the vortex shedding occurs for both cylinders for gaps L/D > 4.0 and the wake behind the downstream cylinder is formed by the combination of vortex shed of both cylinders. Secondly, numerical simulations considering downstream elastically mounted cylinder for L/D = 5.25 are analysed for Reynolds numbers ranging from 100 to 140. It shows that the resonance occurred for Reynolds numbers between 115 and 120, unlike the range obtained for a single cylinder, from 102 to 113, submitted to the same conditions. Furthermore, the maximum dimensionless amplitude of oscillation is 0.721 for Re = 118, which is much higher than the one of the single cylinder (0.422 for Re = 103). The interaction between cylinders changes the Strouhal number in relation to the one of the single cylinder; because of this, there are differences between the lock-in regions

Effects of air temperature on physiology and productive performance of pigs during growing and finishing phases

Thirty-six castrated male pigs were used to determine the influence of thermal environment and reduction of consumption on performance and carcass composition. Animals were housed in two climate chambers. In one, animals were in thermal comfort (TN) (22 °C), and in the other, pigs were under heat stress (HS) (34 °C). Animals were distributed in a randomized block design, making three treatments (TN, HS and animals in thermal comfort with food consumption paired with that observed in HS (PFTN)), with six replicates and two animals per experimental unit. Data were obtained on performance and carcass composition. The weight gains of HS and PFTN animals were reduced by 40.5% and 34.7%, respectively, reflecting a reduction of 13.2% in the final weight of PFTN animals. Triiodothyronine concentration was not affected by heat, but there was an increase in lymphocyte numbers in PFTN animals. The HS and PFTN animals showed lower hot carcass weight. However, there were no effects on hot carcass yield and relative weights of heart, lung and spleen. Heat stress compromised performance. The negative effects of high temperature on pigs include reduction in feed intake and changes in physiology.Keywords: Environment, heat stress, pair feed, pig growth, pig productio

Effect of lunging exercise program with Pessoa training aid on cardiac physical conditioning predictors in adult horses

ABSTRACT The aim of this study was to evaluate the effect the Pessoa training aid (PTA) exercise program exerts in some physical conditioning predictors. Eight detrained adult horses were evaluated in 12 sessions of work with PTA (3 sessions per week). All horses used a heart rate monitor and GPS (V800, Polar Electro) and data was used to calculate energy expenditure (EE), net cost of transport (COT), metabolic energy requirement (Pmet), oxygen pulse, oxygen utilization, heart rate and heart rate variability (HRV). The horses were weighted, and the thoracolumbar shape were measured at the level of the 18th (T18), 13th (T13) and 8th (T8) thoracic vertebrae with a flexible ruler before and after the experimental period. Data obtained weekly were submitted to ANOVA and Tukey test (p≤0.05). Data obtained just before and after the experimental period were submitted to paired t test. There was a decrease in left-right asymmetry. In the third week there was an increase in HR, EE, oxygen pulse and oxygen utilization followed by a decrease in the fourth week. The biomechanics related parameters, COT and Pmet decreased week by week. The HRV showed a sympathetic stimulus in the third week followed by a shift to parasympathetic in the fourth week. We conclude that 12 sessions of lunge exercise with PTA contributed to physical condition improvement