Papers by Johnny J Martinez
Memoria. Investigaciones en Ingeniería, 2021
Resumen.-En este artículo, se desarrolló un algoritmo, basado en la técnica de enjambre de partíc... more Resumen.-En este artículo, se desarrolló un algoritmo, basado en la técnica de enjambre de partículas (Siglas en inglés-PSO) para optimizar los procesos de fundición a presión y por compresión, utilizando modelos matemáticos para describir el comportamiento de ambos procesos. En la fundición por compresión el modelo matemático describe un problema con múltiples objetivos y restricciones, y en la fundición a presión el modelo describe un problema de un solo objetivo con restricciones. El desarrollo del algoritmo PSO se realizó con el software FORTRAN 90, y los resultados se compararon con los obtenidos usando un algoritmo de optimización basado en el proceso de enseñanza-aprendizaje (Siglas en inglés-TLBO), demostrando buenas capacidades en la optimización de parámetros en fundición a presión y por compresión. Se observó que con el algoritmo PSO se consigue una solución óptima en todos los procesos y los tiempos computacionales fueron mínimos. Palabras clave: Optimización de parámetros, fundición por compresión, fundición a presión, algoritmo PSO. Summary.-In this article, an algorithm, based on the particle swarm technique (PSO), is developed to optimize die casting and compression casting processes, using mathematical models to describe the behavior of both processes. In compression casting the mathematical model describes a problem with multiple objectives and constraints, and in die casting the model describes a single objective problem with constraints. The development of the PSO algorithm was carried out with the FORTRAN 90 software, and the results were compared with those reported by a teaching-learning based optimization algorithm, (TLBO), demonstrating good capabilities in the optimization of parameters in die casting and by compression. It was observed that the PSO algorithm achieves an optimal solution in all processes and the computational time were minimal.
24th International Conference on Offshore Mechanics and Arctic Engineering: Volume 3, 2005
The purpose of this paper is to develop a Fourier-Chebyshev collocation spectral method for compu... more The purpose of this paper is to develop a Fourier-Chebyshev collocation spectral method for computing unsteady two-dimensional viscous incompressible flow past a circular cylinder for low Reynolds numbers. The incompressible Navier-Stokes equations (INSE) are formulated in terms of the primitive variables, velocity and pressure. The incompressible Navier-Stokes equations in curvilinear coordinates are spectrally discretized and time integrated by a second-order mixed explicit/implicit time integration scheme. This scheme is a combination of the Crank-Nicolson scheme operating on the diffusive term and Adams-Bashforth scheme acting on the convective term. The projection method is used to split the solution of the INSE to the solution of two decoupled problems: the diffusion-convection equation (Burgers equation) to predict an intermediate velocity field and the Poisson equation for the pressure, it is used to correct the velocity field and satisfy the continuity equation. Finally, th...
Memoria. Investigaciones en Ingeniería, 2021
Resumen.-En el presente estudio se resolvió, usando el método de los volúmenes finitos, un modelo... more Resumen.-En el presente estudio se resolvió, usando el método de los volúmenes finitos, un modelo matemático multifísico en 3D para predecir los fenómenos de flujo de fluidos y transferencia de calor en un molde de colada continua de palanquillas de acero 20CrMnTi. Los resultados mostraron la alta capacidad de enfriamiento del sistema para la formación de una capa sólida progresiva y uniforme que inicia muy cerca del menisco y alcanza a la salida del molde un espesor del 10 % de la sección de la pieza colada. A la salida de la boquilla de entrada sumergida (SEN) el acero experimentó un reflujo con una profundidad de 0,45 m medida desde el menisco. Parte del reflujo en ascenso llegó al menisco y descendió infiltrándose por las paredes del molde. Se observaron velocidades menores a 0,2 m/s en la zona superior del molde y gran penetración del chorro de acero en el centro del molde. Se concluyó, con base en lo descrito en la literatura, lo siguiente: a) El espesor de la costra solidificada, a la salida del molde, es suficiente para evitar roturas en la pieza debido a la presión ferrostática que ejerce el acero líquido, b) Las velocidades en el área del menisco generan baja turbulencia, lo que evita que se produzca atrapamiento de escoria en el acero líquido, c) Las condiciones fluidodinámicas que se presentan en la zona superior del molde, pueden ser contraproducentes para la transferencia de calor en el menisco y la disipación del sobrecalentamiento en el acero.
Resumen.-En el presente estudio se resolvió, usando el método de los volúmenes finitos, un modelo... more Resumen.-En el presente estudio se resolvió, usando el método de los volúmenes finitos, un modelo matemático multifísico en 3D para predecir los fenómenos de flujo de fluidos y transferencia de calor en un molde de colada continua de palanquillas de acero 20CrMnTi. Los resultados mostraron la alta capacidad de enfriamiento del sistema para la formación de una capa sólida progresiva y uniforme que inicia muy cerca del menisco y alcanza a la salida del molde un espesor del 10 % de la sección de la pieza colada. A la salida de la boquilla de entrada sumergida (SEN) el acero experimentó un reflujo con una profundidad de 0,45 m medida desde el menisco. Parte del reflujo en ascenso llegó al menisco y descendió infiltrándose por las paredes del molde. Se observaron velocidades menores a 0,2 m/s en la zona superior del molde y gran penetración del chorro de acero en el centro del molde. Se concluyó, con base en lo descrito en la literatura, lo siguiente: a) El espesor de la costra solidificada, a la salida del molde, es suficiente para evitar roturas en la pieza debido a la presión ferrostática que ejerce el acero líquido, b) Las velocidades en el área del menisco generan baja turbulencia, lo que evita que se produzca atrapamiento de escoria en el acero líquido, c) Las condiciones fluidodinámicas que se presentan en la zona superior del molde, pueden ser contraproducentes para la transferencia de calor en el menisco y la disipación del sobrecalentamiento en el acero.
Vortex-induced vibrations (VIV) of slender structural elements (marine cables, pipes and risers) ... more Vortex-induced vibrations (VIV) of slender structural elements (marine cables, pipes and risers) are very important aspects to be considered in the design stage of many offshore structures, because the fatigue life of risers installed in deep water are often dominated by VIV effects. Despite the relatively fundamental nature of the problem, a small amount is known about the nature of the fluid-structure interaction. The purpose of this paper is to develop a FourierChebyshev collocation spectral method for computing unsteady two-dimensional viscous incompressible flow past a circular cylinder for moderate Reynolds numbers. The incompressible Navier-Stokes equations (INSE) are formulated in terms of the primitive variables, velocity and pressure. The incompressible Navier-Stokes equations in curvilinear coordinates are spectrally discretized and time integrated by a second-order mixed explicit/implicit time integration scheme. This scheme is a combination of the Crank-Nicolson scheme ...
Vortex-induced vibrations (VIV) of slender structural elements (marine cables, pipes and risers) ... more Vortex-induced vibrations (VIV) of slender structural elements (marine cables, pipes and risers) are very important aspects to be considered in the design stage of many offshore structures, because the fatigue life of risers installed in deep water are often dominated by VIV effects. Despite the relatively fundamental nature of the problem, a small amount is known about the nature of the fluid-structure interaction. The purpose of this paper is to develop a Fourier-Chebyshev collocation spectral method for computing unsteady two-dimensional viscous incompressible flow past a circular cylinder for moderate Reynolds numbers. The incompressible Navier-Stokes equations (INSE) are formulated in terms of the primitive variables, velocity and pressure. The incompressible Navier-Stokes equations in curvilinear coordinates are spectrally discretized and time integrated by a second-order mixed explicit/implicit time integration scheme. This scheme is a combination of the Crank-Nicolson scheme...
International Journal of Heat and Fluid Flow, Aug 31, 2003
The viability and accuracy of large-eddy simulation (LES) with wall modeling for high Reynolds nu... more The viability and accuracy of large-eddy simulation (LES) with wall modeling for high Reynolds number complex turbulent flows is investigated by considering the flow around a circular cylinder in the supercritical regime. A simple wall stress model is employed to provide approximate boundary conditions to the LES. The results are compared with those obtained from steady and unsteady Reynolds-averaged Navier–Stokes (RANS) solutions and the available experimental data. The LES solutions are shown to be considerably ...
Memoria de Investigaciones en Ingeniería N°21,2021 by Johnny J Martinez
Optimization of parameters in die casting and compression processes using the particle swarm algorithm, 2021
En este artículo, se desarrolló un algoritmo, basado en la técnica de enjambre de partículas (Sig... more En este artículo, se desarrolló un algoritmo, basado en la técnica de enjambre de partículas (Siglas en inglés - PSO) para optimizar los procesos de fundición a presión y por compresión, utilizando modelos matemáticos para describir el comportamiento de ambos procesos. En la fundición por compresión el modelo matemático describe un problema con múltiples objetivos y restricciones, y en la fundición a presión el modelo describe un problema de un solo objetivo con restricciones. El desarrollo del algoritmo PSO se realizó con el software FORTRAN 90, y los resultados se compararon con los obtenidos usando un algoritmo de optimización basado en el proceso de enseñanza-aprendizaje (Siglas en inglés - TLBO), demostrando buenas capacidades en la optimización de parámetros en fundición a presión y por compresión. Se observó que con el algoritmo PSO se consigue una solución óptima en todos los procesos y los tiempos computacionales fueron mínimos.
In this article, an algorithm, based on the particle swarm technique (PSO), is developed to optimize die casting and compression casting processes, using mathematical models to describe the behavior of both processes. In compression casting the mathematical model describes a problem with multiple objectives and constraints, and in die casting the model describes a single objective problem with constraints. The development of the PSO algorithm was carried out with the FORTRAN 90 software, and the results were compared with those reported by a teaching-learning based optimization algorithm, (TLBO), demonstrating good capabilities in the optimization of parameters in die casting and by compression. It was observed that the PSO algorithm achieves an optimal solution in all processes and the computational time were minimal.
Thermofluidodynamic simulation in a steel continuous casting mold, 2021
En el presente estudio se resolvió, usando el método de los volúmenes finitos, un modelo matemáti... more En el presente estudio se resolvió, usando el método de los volúmenes finitos, un modelo matemático multifísico en 3D para predecir los fenómenos de flujo de fluidos y transferencia de calor en un molde de colada continua de palanquillas de acero 20CrMnTi. Los resultados mostraron la alta capacidad de enfriamiento del sistema para la formación de una capa sólida progresiva y uniforme que inicia muy cerca del menisco y alcanza a la salida del molde un espesor del 10 % de la sección de la pieza colada. A la salida de la boquilla de entrada sumergida (SEN) el acero experimentó un reflujo con una profundidad de 0,45 m medida desde el menisco. Parte del reflujo en ascenso llegó al menisco y descendió infiltrándose por las paredes del molde. Se observaron velocidades menores a 0,2 m/s en la zona superior del molde y gran penetración del chorro de acero en el centro del molde. Se concluyó, con base en lo descrito en la literatura, lo siguiente: a) El espesor de la costra solidificada, a la salida del molde, es suficiente para evitar roturas en la pieza debido a la presión ferrostática que ejerce el acero líquido, b) Las velocidades en el área del menisco generan baja turbulencia, lo que evita que se produzca atrapamiento de escoria en el acero líquido, c) Las condiciones fluidodinámicas que se presentan en la zona superior del molde, pueden ser contraproducentes para la transferencia de calor en el menisco y la disipación del sobrecalentamiento en el acero.
In the present study, a 3D multiphysics mathematical model was solved using the finite volumes method to predict the phenomena of fluid flow and heat transfer in a continuous casting mold of 20CrMnTi steel billets. The results showed the high cooling capacity of the system for the formation of a progressive and uniform solid layer that begins very close to the meniscus and reaches a thickness of 10 % of the section of the casting at the exit of the mold. At the exit of the SEN, the liquid steel underwent a reflux with a depth of 0.45 m measured from the meniscus. Some of the rising reflux reached the meniscus and descended, infiltrating the walls of the mold. Velocities less than 0.2 m/s, in the upper zone of the mold, and great penetration of the steel jet, in the center of the mold, were observed. It was concluded, based on what is described in the literature, the following: a) the thickness of the solidified crust, at the exit of the mold, is sufficient to avoid breakage in the piece due to the ferrostatic pressure exerted by the liquid steel, c) The fluid dynamic conditions that occur in the upper zone of the mold can be counterproductive for the transfer of heat in the meniscus and the dissipation of overheating in the steel.
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Papers by Johnny J Martinez
Memoria de Investigaciones en Ingeniería N°21,2021 by Johnny J Martinez
In this article, an algorithm, based on the particle swarm technique (PSO), is developed to optimize die casting and compression casting processes, using mathematical models to describe the behavior of both processes. In compression casting the mathematical model describes a problem with multiple objectives and constraints, and in die casting the model describes a single objective problem with constraints. The development of the PSO algorithm was carried out with the FORTRAN 90 software, and the results were compared with those reported by a teaching-learning based optimization algorithm, (TLBO), demonstrating good capabilities in the optimization of parameters in die casting and by compression. It was observed that the PSO algorithm achieves an optimal solution in all processes and the computational time were minimal.
In the present study, a 3D multiphysics mathematical model was solved using the finite volumes method to predict the phenomena of fluid flow and heat transfer in a continuous casting mold of 20CrMnTi steel billets. The results showed the high cooling capacity of the system for the formation of a progressive and uniform solid layer that begins very close to the meniscus and reaches a thickness of 10 % of the section of the casting at the exit of the mold. At the exit of the SEN, the liquid steel underwent a reflux with a depth of 0.45 m measured from the meniscus. Some of the rising reflux reached the meniscus and descended, infiltrating the walls of the mold. Velocities less than 0.2 m/s, in the upper zone of the mold, and great penetration of the steel jet, in the center of the mold, were observed. It was concluded, based on what is described in the literature, the following: a) the thickness of the solidified crust, at the exit of the mold, is sufficient to avoid breakage in the piece due to the ferrostatic pressure exerted by the liquid steel, c) The fluid dynamic conditions that occur in the upper zone of the mold can be counterproductive for the transfer of heat in the meniscus and the dissipation of overheating in the steel.
In this article, an algorithm, based on the particle swarm technique (PSO), is developed to optimize die casting and compression casting processes, using mathematical models to describe the behavior of both processes. In compression casting the mathematical model describes a problem with multiple objectives and constraints, and in die casting the model describes a single objective problem with constraints. The development of the PSO algorithm was carried out with the FORTRAN 90 software, and the results were compared with those reported by a teaching-learning based optimization algorithm, (TLBO), demonstrating good capabilities in the optimization of parameters in die casting and by compression. It was observed that the PSO algorithm achieves an optimal solution in all processes and the computational time were minimal.
In the present study, a 3D multiphysics mathematical model was solved using the finite volumes method to predict the phenomena of fluid flow and heat transfer in a continuous casting mold of 20CrMnTi steel billets. The results showed the high cooling capacity of the system for the formation of a progressive and uniform solid layer that begins very close to the meniscus and reaches a thickness of 10 % of the section of the casting at the exit of the mold. At the exit of the SEN, the liquid steel underwent a reflux with a depth of 0.45 m measured from the meniscus. Some of the rising reflux reached the meniscus and descended, infiltrating the walls of the mold. Velocities less than 0.2 m/s, in the upper zone of the mold, and great penetration of the steel jet, in the center of the mold, were observed. It was concluded, based on what is described in the literature, the following: a) the thickness of the solidified crust, at the exit of the mold, is sufficient to avoid breakage in the piece due to the ferrostatic pressure exerted by the liquid steel, c) The fluid dynamic conditions that occur in the upper zone of the mold can be counterproductive for the transfer of heat in the meniscus and the dissipation of overheating in the steel.