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Parameter Study (parameter + study)
Selected AbstractsNumerical parameter study of the thermal behaviour of a gypsum plaster board at fire temperaturesFIRE AND MATERIALS, Issue 2 2008Luc Wullschleger Abstract Based on a comparison between the measured and the calculated temperature evolutions within a gypsum plaster board subject to fire, a numerical parameter study regarding the material properties of gypsum at elevated temperatures has been carried out. This allowed quantifying the individual influence of different quantities and their deviations on the calculated thermal behaviour of this material. Copyright © 2007 John Wiley & Sons, Ltd. [source] An efficient time-domain damping solvent extraction algorithm and its application to arch dam,foundation interaction analysisINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 9 2008Hong Zhong Abstract The dynamic structure,unbounded foundation interaction plays an important role in the seismic response of structures. The damping solvent extraction (DSE) method put forward by Wolf and Song has a great advantage of simplicity, with no singular integrals to be evaluated, no fundamental solution required and convolution integrals avoided. However, implementation of DSE in the time domain to large-scale engineering problems is associated with enormous difficulties in evaluating interaction forces on the structure,unbounded foundation interface, because the displacement on the corresponding interface is an unknown vector to be found. Three sets of interrelated large algebraic equations have to be solved simultaneously. To overcome these difficulties, an efficient algorithm is presented, such that the solution procedure can be greatly simplified and computational effort considerably saved. To verify its accuracy, two examples with analytical solutions were investigated, each with a parameter analysis on the domain size and amount of artificial damping. Then with the parameters suggested in the parameter study, the complex frequency,response functions and earthquake time history analysis of Morrow Point dam were presented to demonstrate the applicability and efficiency of DSE approach. Copyright © 2007 John Wiley & Sons, Ltd. [source] An extended finite element method with analytical enrichment for cohesive crack modelingINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2009James V. CoxArticle first published online: 28 NOV 200 Abstract A recent approach to fracture modeling has combined the extended finite element method (XFEM) with cohesive zone models. Most studies have used simplified enrichment functions to represent the strong discontinuity but have lacked an analytical basis to represent the displacement gradients in the vicinity of the cohesive crack. In this study enrichment functions based upon an existing analytical investigation of the cohesive crack problem are proposed. These functions have the potential of representing displacement gradients in the vicinity of the cohesive crack and allow the crack to incrementally advance across each element. Key aspects of the corresponding numerical formulation and enrichment functions are discussed. A parameter study for a simple mode I model problem is presented to evaluate if quasi-static crack propagation can be accurately followed with the proposed formulation. The effects of mesh refinement and mesh orientation are considered. Propagation of the cohesive zone tip and crack tip, time variation of the cohesive zone length, and crack profiles are examined. The analysis results indicate that the analytically based enrichment functions can accurately track the cohesive crack propagation of a mode I crack independent of mesh orientation. A mixed mode example further demonstrates the potential of the formulation. Copyright © 2008 John Wiley & Sons, Ltd. [source] 1-D numerical modelling of shallow flows with variable horizontal densityINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2010Feifei Zhang Leighton Abstract A1-D numerical model is presented for vertically homogeneous shallow flows with variable horizontal density. The governing equations represent depth-averaged mass and momentum conservation of a liquid,species mixture, and mass conservation of the species in the horizontal direction. Here, the term ,species' refers to material transported with the liquid flow. For example, when the species is taken to be suspended sediment, the model provides an idealized simulation of hyper-concentrated sediment-laden flows. The volumetric species concentration acts as an active scalar, allowing the species dynamics to modify the flow structure. A Godunov-type finite volume scheme is implemented to solve the conservation laws written in a deviatoric, hyperbolic form. The model is verified for variable-density flows, where analytical steady-state solutions are derived. The agreement between the numerical predictions and benchmark test solutions illustrates the ability of the model to capture rapidly varying flow features over uniform and non-uniform bed topography. A parameter study examines the effects of varying the initial density and depth in different regions. Copyright © 2009 John Wiley & Sons, Ltd. [source] Godunov-type adaptive grid model of wave,current interaction at cuspate beachesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2004Benedict D. Rogers Abstract This paper presents a second-order accurate Godunov-type numerical scheme for depth- and period-averaged wave,current interaction. A flux Jacobian is derived for the wave conservation equations and its eigensystem determined, enabling Roe's approximate Riemann solver to be used to evaluate convective fluxes. Dynamically adaptive quadtree grids are used to focus on local hydrodynamic features, where sharp gradients occur in the flow variables. Adaptation criteria based on depth-averaged vorticity, wave-height gradient, wave steepness and the magnitude of velocity gradients are found to produce accurate solutions for nearshore circulation at a half-sinusoidal beach. However, the simultaneous combination of two or more separate criteria produces numerical instability and interference unless all criteria are satisfied for mesh depletion. Simulations of wave,current interaction at a multi-cusped beach match laboratory data from the United Kingdom Coastal Research Facility (UKCRF). A parameter study demonstrates the sensitivity of nearshore flow patterns to changes in relative cusp height, angle of wave incidence, bed roughness, offshore wave height and assumed turbulent eddy viscosity. Only a small deviation from normal wave incidence is required to initiate a meandering longshore current. Nearshore circulation patterns are highly dependent on the offshore wave height. Reduction of the assumed eddy viscosity parameter causes the primary circulation cells for normally incident waves to increase in strength whilst producing rip-like currents cutting diagonally across the surf zone. Copyright © 2004 John Wiley & Sons, Ltd. [source] PREDICTION OF LOCAL SCOUR AROUND BRIDGE PIERS USING ARTIFICIAL NEURAL NETWORKS,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 2 2006Sung-Uk Choi ABSTRACT: This paper describes a method for predicting local scour around bridge piers using an artificial neural network (ANN). Methods for selecting input variables, calibrations of network control parameters, learning process, and verifications are also discussed. The ANN model trained by laboratory data is applied to both laboratory and field measurements. The results illustrate that the ANN model can be used to predict local scour in the laboratories and in the field better than other empirical relationships that are currently in use. A parameter study is also carried out to investigate the importance of each input variable as reflected in data. [source] Anisotropic mass ejection in binary mergersMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2006T. Morris ABSTRACT We investigate the mass loss from a rotationally distorted envelope following the early, rapid in-spiral of a companion star inside a common envelope. For initially wide, massive binaries (M1+M2= 20 M,, P, 10 yr), the primary has a convective envelope at the onset of mass transfer and is able to store much of the available orbital angular momentum in its expanded envelope. Three-dimensional smoothed particle hydrodynamics calculations show that mass loss is enhanced at mid-latitudes due to shock reflection from a torus-shaped outer envelope. Mass ejection in the equatorial plane is completely suppressed if the shock wave is too weak to penetrate the outer envelope in the equatorial direction (typically when the energy deposited in the star is less than about one-third of the binding energy of the envelope). We present a parameter study to show how the geometry of the ejecta depends on the angular momentum and the energy deposited in the envelope during a merging event. Applications to the nearly axisymmetric, but very non-spherical nebulae around SN 1987A and Sheridan 25 are discussed, as well as possible links to RY Scuti and the Small Magellanic Cloud object R4. [source] Induced planet formation in stellar clusters: a parameter study of star,disc encountersMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2005Ingo Thies ABSTRACT We present a parameter study of the possibility of tidally triggered disc instability. Using a restricted N -body model that allows for a survey of an extended parameter space, we show that a passing dwarf star with a mass between 0.1 and 1 M, can probably induce gravitational instabilities (GIs) in the pre-planetary solar disc for prograde passages with minimum separations below 80,170 au for isothermal or adiabatic discs. Inclined and retrograde encounters lead to similar results but require slightly closer passages. Such encounter distances are quite likely in young moderately massive star clusters. The induced GIs may lead to enhanced planetesimal formation in the outer regions of the protoplanetary disc and could therefore be relevant for the existence of Uranus and Neptune, whose formation time-scale of about 100 Myr is inconsistent with the disc lifetimes of about a few Myr according to observational data by Haisch, Lada & Lada. The relatively small gas/solid ratio in Uranus and Neptune can be matched if the perturbing fly-by occurred after early gas depletion of the solar system, i.e. when the solar system was older than about 5 Myr. We also confirm earlier results by Heller that the observed 7° tilt of the solar equatorial plane relative to the ecliptic plane could be the consequence of such a close encounter. [source] Optical, electrical and structural characterization of CuInSe2 thin filmsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 9 2005C. Calderón Abstract Structural, optical and electrical properties of polycrystalline p-type CuInSe2 (CIS) thin films, grown by a process including a chemical reaction between Cu and InxSey thin films deposited sequentially by evaporation, followed by annealing in a Se environment, were studied through XRD (X-ray diffraction), transmittance and Hall voltage measurements. The conditions to grow CIS thin films in the , phase of the chalcopyrite structure were found through a parameter study. CIS films with these characteristics are usually used for the fabrication of high efficiency solar cells. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Process modeling of in situ-adsorption of a bacterial lipaseBIOTECHNOLOGY & BIOENGINEERING, Issue 6 2005Marcus Millitzer Abstract In situ adsorption, known as an in situ-roduct removal (ISPR) technique for low molecular mass bioproducts, was in this study applied to a bacterial exoenzyme proving that this method is also suitable for the separation of macromolecules like proteins. For this, adsorbent particles were added to growing cultures of Staphylococcus carnosusrec., therefore both production and adsorption occurred simultaneously in shaking flasks, stirred tank, or airlift bioreactor as the chosen types of fermenters. The exoenzyme lipase adsorbed rapidly and, after separating cells and adsorbents, desorbed in a packed bed column. Up to 85% of the produced lipase were recovered, fractions of these had been concentrated up to the factor 20 and purified up to a factor of 40 by the procedure. By using the airlift bioreactor an enhancement of biomass production was observed, but the necessity of the addition of an anti-foam reagent resulted in higher product losses in adsorption as well as in desorption. Production and adsorption kinetics have been modeled and applied to in situ-adsorption. The model was used to perform a parameter study in which the influence of biological and physical parameters as well as process parameters on discontinuous and continuous in situ-adsorption was investigated. © 2005 Wiley Periodicals, Inc. [source] | |||||||||||||