An efficient flamelet progress-variable method for modeling non-premixed flames in weak electric fields

Combustion stabilization and enhancement of the flammability limits are mandatory objectives to improve nowadays combustion chambers. At this purpose, the use of an electric field in the flame region provides a solution which is, at the same time, easy to implement and effective to modify the flame structure. The present work describes an efficient flamelet progress-variable approach developed to model the fluid dynamics of flames immersed in an electric field. The main feature of this model is that it can use complex ionization mechanisms without increasing the computational cost of the simulation. The model is based on the assumption that the combustion process is not directly influenced by the electric field and has been tested using two chemi-ionization mechanisms of different complexity in order to examine its behavior with and without the presence of heavy anions in the mixture. Using a one- and two-dimensional numerical test cases, the present approach has been able to reproduce all the major aspects encountered when a flame is subject to an imposed electric field and the main effects of the different chemical mechanisms. Moreover, the proposed model is shown to produce a large reduction in the computational cost, being able to shorten the time needed to perform a simulation up to 40 times.Comment: 26 pages, 13 figures, paper accepted for publication on Computers and Fluid

Kinematic and dynamic forcing strategies for predicting the transport of inertial capsules via a combined lattice Boltzmann-Immersed Boundary method

Modeling the transport of deformable capsules under different flow regimens is crucial in a variety of fields, including oil rheology, blood flow and the dispersion of pollutants. The aim of this study is twofold. Firstly, a combined Lattice Boltzmann-Immersed Boundary (LBM-IB) approach is developed for predicting the transport of inertial deformable capsules. A Moving Least Squares (MLS) scheme has been implemented to correlate the pressure, velocity and force fields of the fluid domain with the capsule dynamics. This computational strategy has been named LBM Dynamic IB. Secondly, this strategy is directly compared with a more conventional approach, named LBM Kinematic IB, where capsules move with the same velocity of the surrounding fluid. Multiple test cases have been considered for assessing the accuracy and efficiency of the Dynamic over Kinematic IB scheme, including the stretching of circular capsules in shear flow, the transport in a plane Poiseuille flow of circular and biconcave capsules, with and without inertia. By monitoring the capsule geometry over time, the two schemes have been documented to be in excellent agreement, especially for low Capillary numbers (Ca $\leq$ 0.01), in the case of non-inertial capsules. Despite a moderate increase in computational burden, the presented LBM Dynamic IB scheme is the sole capable of predicting the dynamics of both non-inertial and inertial deformable capsules. The proposed approach can be efficiently employed for studying the transport of blood cells, cancer cells and nano/micro capsules within a capillary flow

A parallel interaction potential approach coupled with the immersed boundary method for fully resolved simulations of deformable interfaces and membranes

In this paper we show and discuss the use of a versatile interaction potential approach coupled with an immersed boundary method to simulate a variety of flows involving deformable bodies. In particular, we focus on two kinds of problems, namely (i) deformation of liquid-liquid interfaces and (ii) flow in the left ventricle of the heart with either a mechanical or a natural valve. Both examples have in common the two-way interaction of the flow with a deformable interface or a membrane. The interaction potential approach (de Tullio & Pascazio, Jou. Comp. Phys., 2016; Tanaka, Wada and Nakamura, Computational Biomechanics, 2016) with minor modifications can be used to capture the deformation dynamics in both classes of problems. We show that the approach can be used to replicate the deformation dynamics of liquid-liquid interfaces through the use of ad-hoc elastic constants. The results from our simulations agree very well with previous studies on the deformation of drops in standard flow configurations such as deforming drop in a shear flow or a cross flow. We show that the same potential approach can also be used to study the flow in the left ventricle of the heart. The flow imposed into the ventricle interacts dynamically with the mitral valve (mechanical or natural) and the ventricle which are simulated using the same model. Results from these simulations are compared with ad- hoc in-house experimental measurements. Finally, a parallelisation scheme is presented, as parallelisation is unavoidable when studying large scale problems involving several thousands of simultaneously deforming bodies on hundreds of distributed memory computing processors

Associação entre características da amamentação e peso de bezerros da raça Canchim e cruzados Canchim X Nelore.

Avaliação da relação do numero de mamadas diárias (NM), duração da mamada (DM), e tempo total diário de amamentação (TT) com o peso de bezerros canchim (14) e 1/2 Canchim + 1/2 Nelore (13) e com produção de leite das vacas Canchim e Nelore

Comportamento de pastejo de vacas das raças Canchim e Nelore.

Avaliação do tempo de pastejo de vacas das raças Canchim e Nelore paridas de agosto a outubro de 1989, amamentando bezerros canchins e 1/2 Camchi + 1/2 Nelore, respectivamente.Resumo

Espessura de gordura externa e cortes do traseiro especial de machos não-castrados para produção do bovino jovem.

Foi realizado confinamento de 18 machos nao-castrados de cada um dos grupos geneticos Blonde d'Aquitaine X Nelore (BN), Canchim (CA), Piemontes X Nelore (PN) e Nelore (NE), abatidos aos 400 (I), 440 (II) e 480 kg (III) de peso vivo (TRAT); exceto para NE que foram abatidos aos 380, 410 e 440 kg. O peso do traseiro especial (TEE) foi influenciado (P0,05) pelo TRAT.Resumo expandid

Correlação entre produção e componentes do leite em gado de corte.

Este experimento teve como objetivo avaliar a produção e a composição do leite de vacas das raças Canchim e Nelore, tendo em vista o manejo da fase de cria de bovinos de corte

Relação do peso a desmama de bezerros da Raça Canchim e cruzados canchim x Nelore com constituintes do leite.

O trabalho teve como objetivo avaliar a importância das produções totais de proteÍnas, gordura e extrato seco total no leite, em 34 semanas de bezerros da raca Canchim e cruzados 1/2 Canchim + 1/2 Nelore.Resumo

Desenvolvimento de bezerros de corte: influência da produção de leite.

Efeitos de produção total de leite da vaca, em 231 dias de lactação sobre o peso do bezerro a desmama e das produções mensais do leite sobre o ganhos de peso mensais