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Successful Simulation (successful + simulation)
Selected AbstractsLong-term investigations of the snow cover in a subalpine semi-forested catchmentHYDROLOGICAL PROCESSES, Issue 2 2006Manfred Stähli Abstract To improve spring runoff forecasts from subalpine catchments, detailed spatial simulations of the snow cover in this landscape is obligatory. For more than 30 years, the Swiss Federal Research Institute WSL has been conducting extensive snow cover observations in the subalpine watershed Alptal (central Switzerland). This paper summarizes the conclusions from past snow studies in the Alptal valley and presents an analysis of 14 snow courses located at different exposures and altitudes, partly in open areas and partly in forest. The long-term performance of a physically based numerical snow,vegetation,atmosphere model (COUP) was tested with these snow-course measurements. One single parameter set with meteorological input variables corrected to the prevailing local conditions resulted in a convincing snow water equivalent (SWE) simulation at most sites and for various winters with a wide range of snow conditions. The snow interception approach used in this study was able to explain the forest effect on the SWE as observed on paired snow courses. Finally, we demonstrated for a meadow and a forest site that a successful simulation of the snowpack yields appropriate melt rates. Copyright © 2006 John Wiley & Sons, Ltd. [source] Explicit integration of bounding surface model for the analysis of earthquake soil liquefactionINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 15 2010Konstantinos I. Andrianopoulos Abstract This paper presents a new plasticity model developed for the simulation of monotonic and cyclic loading of non-cohesive soils and its implementation to the commercial finite-difference code FLAC, using its User-Defined-Model (UDM) capability. The new model incorporates the framework of Critical State Soil Mechanics, while it relies upon bounding surface plasticity with a vanished elastic region to simulate the non-linear soil response. Stress integration of constitutive relations is performed using a recently proposed explicit scheme with automatic error control and substepping, which so far has been employed in the literature only for constitutive models aiming at monotonic loading. The overall accuracy of this scheme is evaluated at element level by simulating cyclic loading along complex stress paths and by using iso-error maps for paths involving change of the Lode angle. The performance of the new constitutive model and its stress integration scheme in complex boundary value problems involving earthquake-induced liquefaction is evaluated, in terms of accuracy and computational cost, via a number of parametric analyses inspired by the successful simulation of the VELACS centrifuge Model Test No. 2 studying the lateral spreading response of a liquefied sand layer. Copyright © 2009 John Wiley & Sons, Ltd. [source] SANISAND: Simple anisotropic sand plasticity modelINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 8 2008Mahdi Taiebat Abstract SANISAND is the name used for a family of simple anisotropic sand constitutive models developed over the past few years within the framework of critical state soil mechanics and bounding surface plasticity. The existing SANISAND models use a narrow open cone-type yield surface with apex at the origin obeying rotational hardening, which implies that only changes of the stress ratio can cause plastic deformations, while constant stress-ratio loading induces only elastic response. In order to circumvent this limitation, the present member of the SANISAND family introduces a modified eight-curve equation as the analytical description of a narrow but closed cone-type yield surface that obeys rotational and isotropic hardening. This modification enables the prediction of plastic strains during any type of constant stress-ratio loading, a feature lacking from the previous SANISAND models, without losing their well-established predictive capability for all other loading conditions including the cyclic. In the process the plausible assumption is made that the plastic strain rate decomposes in two parts, one due to the change of stress ratio and a second due to loading under constant stress ratio, with isotropic hardening depending on the volumetric component of the latter part only. The model formulation is presented firstly in the triaxial stress space and subsequently its multiaxial generalization is developed following systematically the steps of the triaxial one. A detailed calibration procedure for the model constants is presented, while successful simulation of both drained and undrained behavior of sands under constant and variable stress-ratio loadings at various densities and confining pressures is obtained by the model. Copyright © 2007 John Wiley & Sons, Ltd. [source] Simulation of lid-driven cavity flows by parallel lattice Boltzmann method using multi-relaxation-time schemeINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 9 2004J.-S. Wu Abstract Two-dimensional near-incompressible steady lid-driven cavity flows (Re = 100,7,500) are simulated using multi-relaxation-time (MRT) model in the parallel lattice Boltzmann BGK Bhatnager,Gross,Krook method (LBGK). Results are compared with those using single-relaxation-time (SRT) model in the LBGK method and previous simulation data using Navier,Stokes equations for the same flow conditions. Effects of variation of relaxation parameters in the MRT model, effects of number of the lattice points, improved computational convergence and reduced spatial oscillations of solution near geometrically singular points in the flow field using LBGK method due to MRT model are highlighted in the study. In summary, lattice Boltzmann method using MRT model introduces much less spatial oscillations near geometrical singular points, which is important for the successful simulation of higher Reynolds number flows. Copyright © 2004 John Wiley & Sons, Ltd. [source] Investigating the simulation of cloud microphysical processes in numerical models using a one-dimensional dynamical frameworkATMOSPHERIC SCIENCE LETTERS, Issue 3 2009Christopher Dearden Abstract This paper describes the method by which the performance of a suite of microphysics schemes of varying levels of complexity can be compared within an idealised framework. The purpose is to establish the level of microphysical sophistication required for the successful simulation of liquid clouds in operational models, paying particular attention to the required level of coupling with aerosols. Initial results from a lagrangian parcel model are able to demonstrate the importance of the treatment of droplet activation in dual moment schemes for predicting droplet number qualitatively. Subsequent testing within a one-dimensional (1D) column model using the existing factorial method (FM) will aim to quantify the importance of microphysical complexity on precipitation and cloud albedo relative to the effects of meteorology. Copyright © 2009 Royal Meteorological Society [source] Sensitivity Study on Modeling an Internal Airlift Loop Reactor Using a Steady 2D Two-Fluid ModelCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 12 2008Q. Huang Abstract The sensitivity study of bubbly flow in an internal airlift loop reactor is presented using a steady Reynolds averaging two-fluid model. Comparative evaluation of different drag formulations, drag coefficient correlations, turbulence effect on the drag coefficient, outlet slip velocity, and bubble size is performed and the respective influence to the simulation results is highlighted. It is found that a complicated drag formulation may not result in reliable predictions. All the drag coefficient correlations underpredict the gas holdup if the influence of turbulence on the drag coefficient is not well incorporated. Fortunately, the global hydrodynamics is not sensitive to the outflow slip velocity for a wide range, so a steady two-fluid model can be used to simulate the bubbly flow when the flow field is fully developed. The correct estimation of bubble size with properly selected correlations play an important role in successful simulation of gas-liquid bubbly flow in airlift loop reactors. [source] | ||||||||||