Boundary Condition Sensitivity Analysis Research Articles

WITHDRAWN: Sensitivity analysis of boundary conditions on a series hybrid electric vehicle components through the artificial neural network

WITHDRAWN: Sensitivity analysis of boundary conditions on a series hybrid electric vehicle components through the artificial neural network

Uncertainty and sensitivity analysis of boundary conditions during water droplet phase change regimes

This paper presents the heat and mass transfer model of a liquid droplet in the consistently changing condensation, transit and equilibrium evaporation regimes, and iterative scheme of numerical simulation of the instantaneous temperature of a semi-transparent droplet in the case of complex radiative-convective heating. The whole cycle of the phase transition regimes of medium and large water droplets flowing in the flue gas was modeled, taking into account the application of water spraying into the flue gas of a biofuel furnace. Simulation results expressed as thermal, energy and phase transformation parameters of water droplets are analyzed in the universal Fourier time scale. The factors defining the change of heat transfer regime of a water droplet are termed as the suppression of droplet slipping in flue gas flow at initial phase transformation stage, and the decrease of radiation absorption at the final stage. Particular attention is paid to the evaluation of the influence of parameters defining the interaction of complex transfer processes on the droplet's phase transformations performing the sensitivity analysis of the heat and mass transfer parameters for the “hypothetical” droplet case (the diameter and the slipping velocity in to gas did not change). It is substantiated, that the main parameters defining the sensitivity of water droplets equilibrium evaporation temperature are flue gas humidity, droplets dispersity, flue gas temperature and droplets slipping velocity.The performed statistical uncertainty and sensitivity analysis showed that the uncertainty of heat and mass transfer parameters describing the phase transformations of a water droplet until equilibrium evaporation regime is affected mostly by droplet dispersity, slipping velocity, flue gas temperature and pressure. The size of droplets and their slip velocity in the flue gas flow were identified as very important parameters for the interaction of complex heat and mass transfer processes of a sprayed water. The main uncertainties were defined at the transition from condensing to transit evaporation regime, and it was defined that with a confidence interval of at least 95 % and accepting a tolerance limit with a probability of at least 95 %, the transit evaporation regime starts at the range Fo ≈ (0.02–0.1). The droplet surface temperature, i.e. parameter determining the droplet phase transformations and its dynamics, could be assessed with a mean error of ±10 %, accepting 95 % probability with 95 % confidence level.

Sensitivity analysis based multi-scale methods of coupled path-dependent problems

In the paper, a generalized essential boundary condition sensitivity analysis based implementation of text {FE}^2 and mesh-in-element (MIEL) multi-scale methods is derived as an alternative to standard implementations of multi-scale analysis, where the calculation of Schur complement of the microscopic tangent matrix is needed for bridging the scales. The paper presents a unified approach to the development of an arbitrary MIEL or text {FE}^2 computational scheme for an arbitrary path-dependent material model. Implementation is based on efficient first and second order analytical sensitivity analysis, for which automatic-differentiation-based formulation of essential boundary condition sensitivity analysis is derived. A fully consistently linearized two-level path-following algorithm is introduced as a solution algorithm for the multi-scale modeling. Sensitivity analysis allows each macro step to be followed by an arbitrary number of micro substeps while retaining quadratic convergence of the overall solution algorithm.

Boundary condition sensitivity analysis of the stochastic flow equation

The effect of random vs deterministic boundary conditions on the direct solution of one- and two-dimensional flow systems was examined. The one-dimensional case allows exact analytical solutions for the hydraulic gradient for various boundary conditions. The results demonstrate how a simple modeling choice (i.e. random vs deterministic boundary conditions) can make a significant difference in the mean and variance of the hydraulic gradient. The two-dimensional system models the location of constant head boundaries and no-flow boundaries as random. In the case of steady-state flow in a rectangular domain, a relatively constant increase in head variance was found throughout the domain. Finally, we show that no-flow boundaries whose positions are deterministically known, lower the head variance at points near the boundaries more than at the boundaries themselves.

Energy release rates of crack kinking by boundary condition sensitivity analysis

The energy release rate, which is the total derivative of the energy with respect to crack length, is recognized as corresponding to the shape sensitivity analysis with the crack length change represented by the tangential component of design velocity. In this paper the sensitivity formula recently developed for a changing boundary condition has been further extended to cover crack kinking under mixed mode loading. Due to difficulty in defining the velocity field at the corner, the energy release rate at the onset of crack kinking is obtained by extrapolating the energy release rates for finite length kinked cracks. A rectangular plate with a single edge slant crack under uniform tension is taken as a numerical example. The multi-region technique in the numerical implementation of the boundary integral equation is adopted to consider the asymmetry of the problem. Excellent accuracy is observed as compared with reference analytic solutions.

Sensitivity Analysis And Optimization By TheBEM For Volume Integral Functionals

Boundary condition sensitivity analysis and optimization is investigated with respect to volume integral functionals for thermal problems. General sensitivity expressions are derived by the adjoint variable method. Harmonic primary and biharmonic adjoint sources are handled with higherorder fundamental solutions in the BEM disci, -tization of the problems. Numerical sensitivities are compared with 1-dim. exact solutions, whilst a constrained optimization problem involving a turbine blade profile is investigated for practical interest.