ENCIT2012-349 SIMULATION OF RADIAL POLLUTANT MOTION IN POLYTRPIC ATMOSPHERES ACCOUNTIG FOR POLLUTANT DECAY - PDF
Maria Laura Martins-Costa, UFF, Brazil
Rogério M. Saldanha da Gama, UERJ, Brazil
Abstract: A hyperbolic model, that admits discontinuities in addition to smooth or classical solutions, describes the radial motion and decay of a pollutant immersed in a polytrophic atmosphere, resulting from mass and momentum conservation for the air-pollutant mixture and the pollutant mass balance. The numerical approximation combines Glimm's method (requiring the solution of a Riemann problem for each two consecutive steps) with an operator splitting technique. Some representative results considering a spherical shell configuration are presented.
Keywords:Glimm's scheme; operator splitting; pollutant transport; polytropic atmosphere.
Presentation Schedule: Monday, 17:00-17:20. Session: FMR5-1. Presenter: Rogério M. Saldanha da Gama.
ENCIT2012-391 A NON-CLASSICAL RIEMANN PROBLEM FOR PIG MOTION IN ISOTHERMAL GAS PIPELINES - PDF
Simone Rodrigues de Melo, Felipe Bastos de Freitas Rachid, UFF, Brazil
Abstract: This paper presents the formulation along with its analytical solution of a non-classical Riemann problem for pig motion in transient isothermal gas pipelines. The pig modeling takes into account the existence of flow rate by-pass through its gap as well as through its body. Coulomb type as well as hydrodynamic friction forces are accounted for at the pig-pipe lateral interface. The proposed formulation is suitable for using with numerical methods based on the Riemann problem solution, such as Godunov, Glimm and MUSCL-Hancock schemes and others. Numerical solutions for the non-classical Riemann problem are presented for start-up the pig inside the line, for pigs with and without by-pass flow rates.
Keywords:Pig motion; gas pipelines; Riemann problem; non-classical Riemann problem.
Presentation Schedule: Monday, 17:20-17:40. Session: FMR5-1. Presenter: Simone Rodrigues de Melo.
ENCIT2012-392 HYSTERESIS LOOPS DUE TO GASEOUS CAVITATION - PDF
Agnaldo Borges da Silva, Felipe Bastos de Freitas Rachid, UFF, Brazil
Abstract: This work presents a consistent thermodynamic model to describe the gas release phenomenon in homogeneous liquid-gas flows undergoing isothermal transformations. The liquid-gas mixture is regarded as a pseudo-fluid whose constitutive behavior is obtained from two thermodynamic potentials - the Helmholtz free energy and a pseudo-potential of dissipation. Thanks to the inclusion of the concentration of dissolved gas in the liquid in the list of state variables, along with the gas volume fraction and the mass densities of the liquid and gas constituents, a suitable and simple expression for the rate of gas release is derived. Besides of unconditionally satisfying the Second Law of the Thermodynamics, the proposed expression is capable to properly describe experimental data available in the literature with great accuracy for a relatively wide range of saturation pressures. Numerical simulations carried out for an air-water mixture, subjected to a single expansion and cyclic expansion-contraction loadings, illustrate the influence of the gas release on the mechanical response of the fluid, which exhibits dispersion and attenuation and also hysteresis.
Keywords:gaseous cavitation; free gas; internal variables theory; irreversible processes.
Presentation Schedule: Thursday, 16:20-16:40. Session: FMR6-2. Presenter: Agnaldo Borges da Silva.
ENCIT2012-158 STEADY DISCHARGE COEFFICIENT IN INTERNAL COMBUSTION ENGINE - PDF
Bruno Souza Soriano, Charles Rech, ULBRA, Brazil
Flavio Vanderlei Zancanaro Júnior, Horácio Antonio Vielmo, UFRGS, Brazil
Abstract: The breathing capacity of the intake system in internal combustion engine is quantified in terms of discharge coefficient (CD). In this paper, the steady discharge coefficient was investigated numerically and validated experimentally. Steady experimental data was obtained for various valve lift and suction pressure. The suction pressure, generated by a fan, was utilized as boundary condition for the numerical simulation. The air mass flow was measured with a commercial hot film anemometer sensor.Its characteristic curve was obtained with an standard orifice plate. The air mass sensor was connected to a data acquisition board (National Instruments 6221) and its original LabVIEW software. In order to calculate the global discharge coefficient, the valve lift refered to the angular position of the crankcase was measured with a rotary encoder with a resolution of 0.175 degree and a length gauge with an accuracy of ± 0.2 \&\#956;m. The numerical simulation uses a commercial Finite Volumes CFD code. Regarding turbulence, computations were performed with adequated model. A detailed mesh independence study was performed.
Keywords:CFD; Internal combustion engine; Discharge coefficient.
Presentation Schedule: Tuesday, 18:00-18:20. Session: AES3-2/AES2. Presenter: Bruno Souza Soriano.
ENCIT2012-142 EXPERIMENTAL MEASUREMENTS OF PRESSURE WAVES IN INTAKE SYSTEM OF A CFR ENGINE - PDF
Carlos Eduardo Guex Falcão, Fabiano Disconzi Wildner, Pedro Barbosa Mello, Horácio Antonio Vielmo, UFRGS, Brazil
Charles Rech, Bruno Souza Soriano, ULBRA, Brazil
Abstract: The understanding of the pressure waves behavior in the air intake system of an internal combustion engine has immediate practical interests and is very important to develop the system and increase its efficiency. The periodic movement of the intake valve originates a pulsating phenomenon in the intake manifold. This pressure waves that propagate within the system directly affect the amount of air entering the cylinder. To understand this phenomenon it is important the experimental procedure both to quantify the behavior and establish results for numerical or other experimental comparisons in the future. This paper presents experimental results measurements of pressure waves and mass flow that occurs in the intake manifold system of a standard CFR (Cooperative Fuel Research) engine. The engine under consideration has a bore of 82.55 mm and a stroke of 114.30 mm.
Keywords:manifold; pressure waves.
Presentation Schedule: Tuesday, 18:20-18:40. Session: AES3-2/AES2. Presenter: Charles Rech.
ENCIT2012-373 SATURATION OF A FLOW THROUGH A RIGID POROUS MEDIUM BOUNDED BY AN IMPERMEABLE WALL: A CONSTRAINED NONLINEAR HYPERBOLIC SYSTEM - PDF
Rogério M. Saldanha da Gama, José Julio Pedrosa Filho, UERJ, Brazil
Maria Laura Martins-Costa, UFF, Brazil
Abstract: This work proposes a mathematical model to study the filling up of an unsaturated rigid porous medium by a liquid identifying the transition from unsaturated to saturated flow and accounting for the physical upper bound of the fluid fraction that depends on the volume of the pores. The complete solution of a Riemann problem associated to the system of conservation laws satisfying the constraint given by the saturation upper bound is presented.
Keywords:Flow through unsaturated porous media; transition saturated/unsaturated flow; Riemann problem; constrained unknown; shock waves.
Presentation Schedule: Monday, 17:40-18:00. Session: FMR5-1. Presenter: Rogério M. Saldanha da Gama.