Open Access
ARTICLE
M. O. Doğan1,2, H. Class2, R. Helmig2
CMES-Computer Modeling in Engineering & Sciences, Vol.53, No.3, pp. 207-234, 2009, DOI:10.3970/cmes.2009.053.207
Abstract Many flow problems in environmental, technical and biological systems are characterized by a distinct interaction between a flow region in porous-medium and a free-flow region in quasi-one-dimensional hollow structures. In this study, different model concepts, based on a dual-continuum strategy, for the simulation of coupled porous-media flow and (lower-dimensional) pipe flow are further developed and tested. The dual-continuum concept is extended for coupling multi-phase porous-media flow with lower-dimensional single-phase free flow. The complexity of the considered flow regimes is increased gradually. Examples are given for a coupled single-phase incompressible and compressible flow in both porous-media and pipe flow domains. Furthermore,… More >
Open Access
ARTICLE
A. Colombo1, U. Galvanetto2
CMES-Computer Modeling in Engineering & Sciences, Vol.53, No.3, pp. 235-254, 2009, DOI:10.3970/cmes.2009.053.235
Abstract The paper addresses the problem of computing the stable manifolds of equilibria and limit cycles of saddle type in piecewise smooth dynamical systems. All singular points that are generically present along one-dimensional or two-dimensional manifolds are classified and such a classification is then used to define a method for the numerical computation of the stable manifolds. Finally the proposed method is applied to the case of a stick-slip oscillator. More >
Open Access
ARTICLE
D. Gawin1, L. Sanavia2
CMES-Computer Modeling in Engineering & Sciences, Vol.53, No.3, pp. 255-302, 2009, DOI:10.3970/cmes.2009.053.255
Abstract This paper presents a unified mathematical approach to model the hydro-thermo-mechanical behavior of saturated and partially saturated porous media by considering the effects of air dissolved in liquid water. The model equations are discretized by means of the Finite Element method. A correspondingly updated code is used to analyze two examples; the first one is the well known Liakopoulos test, i.e. the drainage of liquid water from a 1m column of sand, which is used to validate numerically the model here developed. As second example, a biaxial compression test of undrained dense sands where cavitation takes place at strain localization… More >
Open Access
ARTICLE
A. Carpinteri1, M. Paggi1,2, G. Zavarise3
CMES-Computer Modeling in Engineering & Sciences, Vol.53, No.3, pp. 303-326, 2009, DOI:10.3970/cmes.2009.053.303
Abstract The stick-slip instability is a typical manifestation of the nonlinearity of the frictional response of rough surfaces. As recently demonstrated by several researchers, the problem of contact loss is also inherently connected to the stick-slip instability and it has been detected both in elastically soft materials, such as rubber or gelatine, and in elastic stiff materials, such as for earthquake faults. Treating the problem of tangential contact in the framework of micromechanical contact models, the effect of the phenomenon of contact loss on the micro-slip behavior of rough surfaces is herein investigated. To this aim, the stick and slip components… More >
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