Numerical Heat Transfer and Fluid Flow

4thermophysical properties, etc. In turn, this causes variation in a wide range of the process parameters subject to control. In such a situation, application of the results obtained by analysis of linear models is very problematic and even unfeasible in most cases.The search for new approaches to analysis of nonlinear models is an important element in solution of the problem of optimal control of power equipment using non-certified fuel of a variable composition. Literature review and problem statementAn effective way to simplify the study of complex models is to make them dimensionless. Reduction of dimensionality of the modeling space makes it possible both to reduce number of experimental (full-scale and numerical) studies by IntroductionWhen studying behavior of control systems, dynamic conditions require special consideration. Apparatus of ordinary differential equations is most often used as a mathematical tool for studying such systems. General methods of solution have only their linear forms. For this reason, linear (linearized) approaches are used to construct models of object and controller. However more exact models are represented by nonlinear differential equations. This situation leads to the fact that the results obtained can only be used within the range of small variation of parameters of the controlled processes nearby the linearization point.The use of fuel of a variable composition [1,2] in power equipment instead of certified fuel with a constant composition brings about a continuous variation of the fuel calorific value, amount of combustion products, their temperature, MATHEMATICS AND CYBERNETICS -APPLIED ASPECTS DEVELOPMENT OF

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“…The Navier-Stokes equations are a particular expression of the generalized conservation law [15] which can be written in a vector form as:…”

Section: Fo T Fo T Ho a T A T T L Lmentioning

confidence: 99%

Development of a method for approximate solution of nonlinear ordinary differential equations using pendulum motion as an example

Brunetkin

Maksymov

Maksymova

et al. 2017

EEJET

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“…The standard methods provide only the limit case solutions, with the CD approximation giving the solution when there is no flow and the UW approximation giving the solution, when there are no viscous forces acting on the flow. This issue can be resolved if we use the exponential/hybrid schemes (as described in [1]), in which the flux approximation is based on the balance of the convective and viscous forces experienced by the fluid. Besides convective and viscous forces, the flux also depends on the pressure gradient normal to the interface and the gradient of the cross-flux or the transverse flux, which is parallel to the interface, which can be treated as source terms for the conservation law.…”

Section: Introductionmentioning

confidence: 99%

Flux Approximation Scheme for the Incompressible Navier-Stokes Equations Using Local Boundary Value Problems

Kumar

Boonkkamp

Koren

2016

Lecture Notes in Computational Science and Engineering

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Abstract. We present a flux approximation scheme for the incompressible NavierStokes equations, that is based on a flux approximation scheme for the scalar advection-diffusion-reaction equation that we developed earlier. The flux is computed from local boundary value problems (BVPs) and is expressed as a sum of a homogeneous and an inhomogeneous part. The homogeneous part depends on the balance of the convective and viscous forces and the inhomogeneous part depends on source terms included in the local BVP.

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“…Temporal discretization involves the integration of the terms of the differential equations over a time step ∆t, which needs to be defined. More information about the temporal discretization schemes might be found in [83].…”

Section: Temporal Discretizationmentioning

confidence: 99%

Methodology for the Numerical Characterization of a Radial Turbine under Steady and Pulsating Flow

Peña¹

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iii AbstractThe increasing use of turbochargers is leading to an outstanding research to understand the internal flow in turbomachines. In this frame, computational fluid dynamics (CFD) is one of the tools that can be applied to contribute to the analysis of the fluid-dynamic processes occurring in a turbine. The objective of this thesis is the development of a methodology for performing simulations of radial turbomachinery optimizing the available computational resources. This methodology is used for the characterization of a vaned-nozzle turbine under steady and pulsating flow conditions. An important effort has been devoted in adjusting the case configuration to maximize the accuracy achievable with a certain computational cost. Concerning the cell size, a local mesh independence analysis is proposed as a procedure to optimize the distribution of cells in the domain, thus allowing to use a finer mesh in the most suitable places. Particularly important in turbomachinery simulations is the influence of the approach for simulating rotor motion. In this thesis two models have been compared: multiple reference frame and sliding mesh. The differences obtained using both methods were found to be significant in off-design regions. Steady flow CFD results have been validated against global measurements taken on a gas-stand.The modeling of a turbine, installed either on a turbocharger test rig or an engine, requires the calculation of the flow in the ducts composing the system. Those ducts could be simulated assuming a one-dimensional (1D) approximation, and thus reducing the computational cost. In this frame of ideas, two CFD boundary conditions have been developed. The first one allows performing coupled 1D-3D simulations, communicating the flow variables from each domain through the boundary. The second boundary condition is based in a new formulation for a stand-alone anechoic end, which intends to represent the flow behavior of an infinite duct.Finally, the turbine was simulated under engine-like pulsating conditions. The pulsating effects are analyzed separately in the different components of the turbine and are compared with the results obtained in equivalent steady simulations, in order to evaluate their quasi-steadiness. The information from the computations is used to describe the unsteady flow in the turbine components, and thus, contribute to engine modeling by the implementation of a new turbine model for its use in 1D codes. v Resumen La alta implantación de la sobrealimentación está propiciando un enorme avance en la comprensión del flujo interno en turbomaquinas . La mecánica de fluidos computacional (CFD) es una de las herramientas que pueden aplicarse para contribuir al análisis de los fenómenos fluido-dinámicos en la turbina. El objetivo de la presente tesis es el desarrollo de una metodología para realizar simulaciones de turbomaquinaría radial, optimizando los recursos computacionales disponibles. Esta metodología se emplea para caracterizar una turbina con un estator alabeado en condiciones de flu...

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Numerical Heat Transfer and Fluid Flow

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Development of a method for approximate solution of nonlinear ordinary differential equations using pendulum motion as an example

Development of a method for approximate solution of nonlinear ordinary differential equations using pendulum motion as an example

Flux Approximation Scheme for the Incompressible Navier-Stokes Equations Using Local Boundary Value Problems

Methodology for the Numerical Characterization of a Radial Turbine under Steady and Pulsating Flow

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