An hp‐adaptive unstructured finite volume solver for compressible flows

The idea of hp‐adaptation, which has originally been developed for compact schemes (such as finite element methods), suggests an adaptation scheme using a mixture of mesh refinement and order enrichment based on the smoothness of the solution to obtain an accurate solution efficiently. In this paper, we develop an hp‐adaptation framework for unstructured finite volume methods using residual‐based and adjoint‐based error indicators. For the residual‐based error indicator, we use a higher‐order discrete operator to estimate the truncation error, whereas this estimate is weighted by the solution of the discrete adjoint problem for an output of interest to form the adaptation indicator for adjoint‐based adaptations. We perform our adaptation by local subdivision of cells with nonconforming interfaces allowed and local reconstruction of higher‐order polynomials for solution approximations. We present our results for two‐dimensional compressible flow problems including subsonic inviscid, transonic inviscid, and subsonic laminar flow around the NACA 0012 airfoil and also turbulent flow over a flat plate. Our numerical results suggest the efficiency and accuracy advantages of adjoint‐based hp‐adaptations over uniform refinement and also over residual‐based adaptation for flows with and without singularities.     

Simulation of flow‐flexible body interactions with large deformation

A modified front‐tracking method was proposed for the simulation of fluid‐flexible body interactions with large deformations. A large deformable body was modeled by restructuring the body using a grid adaptation. Discontinuities in the viscosity at the fluid‐structure interface were incorporated by distributing the viscosity across the interface using an indicator function. A viscosity gradient field was created near the interface, and a smooth transition occurred between the structure and the fluid. The fluid motion was defined on the Eulerian domain and was solved using the fractional step method on a staggered Cartesian grid system. The solid motion was described by Lagrangian variables and was solved by the finite element method on an unstructured triangular mesh. The fluid motion and the structure motion were independently solved, and their interaction force was calculated using a feedback law. The interaction force was the restoring force of a stiff spring with damping, and spread from the Lagrangian coordinates to the Eulerian grid by a smoothed approximation of the Dirac delta function. In the numerical simulations, we validated the effect of the grid adaptation on the solid solver using a vibrating circular ring. The effects of the viscosity gradient field were verified by solving the deformation of a circular disk in a linear shear flow, including an elastic ring moving through a channel with constriction, deformation of a suspended catenary, and a swimming jellyfish. A comparison of the numerical results with the theoretical solutions was presented. Copyright © 2011 John Wiley & Sons, Ltd.     

信息与生命

理解生命的本质的关键，在于信息科学与生物学的结合，以系统和综合的观点去理解生物，综合多种信息对生物体进行分析。生物信息学正是这样一个新兴的交叉学科。     

Numerical analysis of a synthetic jet using an automated adaptive method

An automated adaptive remeshing methodology is applied to a synthetic jet. A set of two‐dimensional, axisymmetric, time‐dependent Computational Fluid Dynamics analyses are performed. Grid independence is achieved via successive levels of adaptive refinement using a novel methodology. The method employs adaptive remeshing, performed in an automated fashion. Adaptation criteria are based upon the undivided differences in select field variables. Sensors are placed at strategic locations within the flow field, which are used to aid in judging grid independence. The resulting analytical predictions are compared to an experimental dataset. The automated methodology yields both a verified and validated set of analysis results for the synthetic jet. Copyright © 2011 John Wiley & Sons, Ltd.     

Adaptation of the Experimental Background (ATEB) Method in Voltammetric Determination of Thujone in Herbal Matrices

In this work, a new baseline correction method, named the Adaptation of The Experimental Background (ATEB), based on the subtraction of the blank sample signal (registered for solution without an analyte, for example a supporting electrolyte), was introduced. However, the method was something more than the simple subtraction of the blank sample signal. An innovation of the algorithm consisted in improving of the blank sample signal through application of the polynomials. Operation of the algorithm was demonstrated in determination of thujone in the synthetic and real samples. The synthetic samples were composed of two different mixtures of the quasi‐absinthe herbal matrices spiked with 0.7–14 mg L⁻¹ of thujone. The measurements were conducted with or without presence of Cu²⁺, which is an interfering agent originating from production of absinthe like alcoholic beverages. The real sample was Rodnik's absinthe, likewise spiked with thujone. Application of the ATEB method enabled calculation of the calibration lines with very good correlation (not lower than 0.997).     

Pacing CFD: automatic mesh adaptation as an efficient tool to improve CFD accuracy

We propose in this paper to demonstrate the impact of mesh adaptation technology on computational fluid dynamics (CFD) solution accuracy. A global methodology is presented that includes a selected number of pre-processing techniques that sensibly improve the quality of the initial meshes and accelerate the solution-adaptation process. Finally, the efficiency of the approach is demonstrated through meaningful numerical tests.     

Dynamic Models of Simple Judgments: II. Properties of a Self-Organizing PAGAN (Parallel, Adaptive, Generalized Accumulator Network) Model for Multi-Choice Tasks

This is the second of two papers comparing connectionist and traditional stochastic latency mechanisms with respect to their ability to account for simple judgments. In the first, we reviewed evidence for a self-regulating accumulator module for two- and three-category discrimination. In this paper, we examine established neural network models that have been applied to predicting response time measures, and discuss their representational and adaptational limitations. We go on to describe and evaluate the network implementation of a Parallel Adaptive Generalized Accumulator Network (PAGAN), based on the interconnection of a number of self-regulating, generalized accumulator modules. The enhancement of PAGAN through the incorporation of distributed connectionist representation is briefly discussed.     

Adaptive finite elements with large aspect ratio for mass transport in electroosmosis and pressure‐driven microflows

A space–time adaptive method is presented for the numerical simulation of mass transport in electroosmotic and pressure‐driven microflows in two space dimensions. The method uses finite elements with large aspect ratio, which allows the electroosmotic flow and the mass transport to be solved accurately despite the presence of strong boundary layers. The unknowns are the external electric potential, the electrical double layer potential, the velocity field and the sample concentration. Continuous piecewise linear stabilized finite elements with large aspect ratio and the Crank–Nicolson scheme are used for the space and time discretization of the concentration equation. Numerical results are presented showing the efficiency of this approach, first in a straight channel, then in crossing and multiple T‐form configuration channels. Copyright © 2009 John Wiley & Sons, Ltd.     

Colour Adaptation in Three Fringe Photoelasticity

Three fringe photoelasticity (TFP) can give the total fringe order from a single colour isochromatic fringe field by suitably comparing the colour with a calibration specimen. The fringe order evaluation can be erroneous when the materials for the calibration specimen and the application specimen are different. This is because of the colour variation between the two materials. This is conventionally handled by preparing individual calibration tables for each application. A new methodology to tune the calibration table obtained for a single material to accommodate the tint variation in TFP is proposed for the use of different specimen materials. Discontinuities in fringe order variation are smoothed using the refined TFP (RTFP) procedure. The elegance of the new methodology for solving a multi-material system is bought out by solving the problem of a bi-material Brazilian disc. The results obtained are compared with the phase shifting technique.