scholarly journals Comparing thixotropic and Herschel–Bulkley parameterizations for continuum models of avalanches and subaqueous debris flows

2018 ◽  
Vol 18 (1) ◽  
pp. 303-319 ◽  
Author(s):  
Chan-Hoo Jeon ◽  
Ben R. Hodges
Keyword(s):  
Experimental Data ◽  
Debris Flows ◽  
Fluid Model ◽  
Liquid Mixtures ◽  
High Yield ◽  
Aging Effects ◽  
Stress Strain ◽  
Experimental Conditions ◽  
Wide Range ◽  
Strain Relationship

Abstract. Avalanches and subaqueous debris flows are two cases of a wide range of natural hazards that have been previously modeled with non-Newtonian fluid mechanics approximating the interplay of forces associated with gravity flows of granular and solid–liquid mixtures. The complex behaviors of such flows at unsteady flow initiation (i.e., destruction of structural jamming) and flow stalling (restructuralization) imply that the representative viscosity–stress relationships should include hysteresis: there is no reason to expect the timescale of microstructure destruction is the same as the timescale of restructuralization. The non-Newtonian Herschel–Bulkley relationship that has been previously used in such models implies complete reversibility of the stress–strain relationship and thus cannot correctly represent unsteady phases. In contrast, a thixotropic non-Newtonian model allows representation of initial structural jamming and aging effects that provide hysteresis in the stress–strain relationship. In this study, a thixotropic model and a Herschel–Bulkley model are compared to each other and to prior laboratory experiments that are representative of an avalanche and a subaqueous debris flow. A numerical solver using a multi-material level-set method is applied to track multiple interfaces simultaneously in the simulations. The numerical results are validated with analytical solutions and available experimental data using parameters selected based on the experimental setup and without post hoc calibration. The thixotropic (time-dependent) fluid model shows reasonable agreement with all the experimental data. For most of the experimental conditions, the Herschel–Bulkley (time-independent) model results were similar to the thixotropic model, a critical exception being conditions with a high yield stress where the Herschel–Bulkley model did not initiate flow. These results indicate that the thixotropic relationship is promising for modeling unsteady phases of debris flows and avalanches, but there is a need for better understanding of the correct material parameters and parameters for the initial structural jamming and characteristic time of aging, which requires more detailed experimental data than presently available.

scholarly journals Comparing Thixotropic and Herschel-Bulkley Models for Avalanches and Subaqueous Debris Flows

2017 ◽  
Author(s):  
Chan-Hoo Jeon ◽  
Ben R. Hodges
Keyword(s):  
Experimental Data ◽  
Newtonian Fluid ◽  
Debris Flows ◽  
Stokes Equations ◽  
Fluid Model ◽  
Newtonian Fluids ◽  
Time Dependent ◽  
High Yield ◽  
Time Space ◽  
Independent Model

Abstract. Debris flows such as avalanches and landslides are heterogeneous mixtures of solids and liquids but are often simulated as homogeneous non-Newtonian fluids using a Herschel-Bulkley model. By representing the heterogeneous debris as a homogeneous non-Newtonian fluid, it is possible to use standard numerical approaches for the Navier-Stokes equations where viscosity is allowed to vary in time and space (e.g. eddy-viscosity turbulence models). Common non-Newtonian models are time-independent so that the relationship between the time-space-varying effective viscosity and flow stress is unchanging. However, the complex behaviors of debris flows at flow initiation (jamming) and cessation (restructuralization) imply that the viscosity-stress relationships should have time-dependent behaviors, which is a feature of thixotropic non-Newtonian fluids. In this paper, both Herschel-Bulkley and thixotropic non-Newtonian fluid models are evaluated for simulating avalanches along a slope and subaqueous debris flows. A numerical solver using a multi-material level set method is applied to track multiple interfaces simultaneously. The numerical results are validated with analytical solutions and available experimental data using parameters selected based on the experimental setup and without post-hoc calibration. The thixotropic (time-dependent) fluid model shows reasonable agreement with all the experimental data. For most of the experimental conditions, the Herschel-Bulkley (time-independent) model results were similar to the thixotropic model, a critical exception being conditions with a high yield stress. Where the flow initiation is strongly dominated by the structural jamming and the initial yield behavior the time-independent model performed poorly.

Dynamic Stress-Strain Relationship of Saturated Clay by Dynamic Triaxial Test

2011 ◽  
Vol 250-253 ◽  
pp. 3183-3186
Author(s):  
Jian Yi Yuan
Keyword(s):  
Triaxial Test ◽  
Dynamic Stress ◽  
Soft Clay ◽  
Confining Pressure ◽  
Dynamic Shear ◽  
Stress Strain ◽  
Dynamic Triaxial Test ◽  
Wide Range ◽  
Strain Relationship ◽  
Relationship Of

Subgrade diseases are exposed more and more serious with raising speed of existing railway in wide range. Fro the complexity of dynamic stress-strain relationship of soil, dynamic triaxial test was used to analyze .the dynamic mechanics behavior under cyclic train load for saturated soft clay in Yangtze Delta region. Compaction coefficient, confining pressure, dynamic shear strsss ratio, inputing stimulus and loading frequence were taken into account in test. The results show that the dynamic stress-strain curves of soil specimen are provided with prominent hysteretic characteristics and area surrounded by hysteretic curves gradually augment and slope of hysteretic curve decreases with the increase of dynamic shear train amplitude. The strong correlation exists between dynamical stress and strain.

Bending of Blood Vessel Wall: Stress-Strain Laws of the Intima-Media and Adventitial Layers

1995 ◽  
Vol 117 (1) ◽  
pp. 136-145 ◽  
Author(s):  
Jiaping Xie ◽  
Jianbo Zhou ◽  
Y. C. Fung
Keyword(s):  
Experimental Data ◽  
Stress State ◽  
Beam Theory ◽  
Nonlinear Least Squares ◽  
Wall Stress ◽  
Wall Material ◽  
Stress Strain ◽  
Strain Relationship ◽  
Residual Strains ◽  
Residual Stresses And Strains

In order to determine the stress-strain relationship of the inner (intima and media) and outer (adventitia) layers of blood vessels in the neighborhood of the zero-stress state, bending experiments were performed on aortic strips of rats. In the experiments, one end of a strip was clamped, and a force was applied on the other end. The deflection curves of the strips were measured. By regarding the aortic strip as a curved beam, the classical beam theory was employed to analyze the strain distribution from the experimental data. A computer program dealing with nonlinear equations and nonlinear least squares optimization was developed. Strains were referred to the zero-stress state. The load-deflection relationship was then used to determine the stress-strain relationship. Certain forms of the stress-strain laws were assumed. The linear laws fit the experimental data accurately, probably because the strains during bending are quite small, although the rotations are large. The Young’s modulus of the inner layer, which consists of endothelial and smooth muscle cells and elastic lamina, was found to be three to four times larger than that of the outer layer which consists of collagen with a small amount of fibroblasts and elastin. The residual stresses and strains at the no-load state were calculated from the deduced stress-strain relationship. It is shown that large errors (up to 50 percent) in the values of the residual strains will occur if the wall material was treated as homogeneous, i.e., if the layered constitution was ignored.

scholarly journals An Incremental Formulation of Constitutive Equations for Deposited Snow

1980 ◽  
Vol 25 (92) ◽  
pp. 289-307 ◽  
Author(s):  
J. Desrues ◽  
F. Darve ◽  
E. Flavigny ◽  
J.P. Navarre ◽  
A. Taillefer
Keyword(s):  
Experimental Data ◽  
Axial Strain ◽  
Triaxial Tests ◽  
Stress Strain ◽  
Theoretical Formulation ◽  
Non Linear ◽  
Incremental Formulation ◽  
Strain Relationship ◽  
Strain Paths ◽  
Incremental Form

Abstract The behaviour of a snow mass under natural loadings (gravity forces, boundary conditions) can be computed by the finite-element method, in so far as a convenient formulation of the stress–strain relationship for snow is available. This paper deals with such a formulation given in incremental form. Experiments have been performed, which show that deposited snow can be considered as a non-linear visco-elastic material with memory effect. The proposed theoretical formulation takes into account these properties. The elastic part of the deformation is assumed to be isotropic and non-linear; the viscous part is expressed in terms of a creep-rate, which results from a superposition of elementary creep-rates according to Boltzmann’s principle. The values of parameters can be obtained from isotropic creep experiments. The experimental data and the resulting parameters are reported. Since the parameters were determined, the formulation of the rheological law was then tested by integration on “stress–strain paths" corresponding to other experiments of a different type, performed on the same snow. The experiments are triaxial tests at constant axial strain-rate, with a preliminary stage of isotropic compression. Experimental data are compared to theoretical curves obtained by integration of the rheological law. The calculated behaviour is consistent with the experimental results.

scholarly journals Continuum-Based Approach to Model Particulate Soil–Water Interaction: Model Validation and Insight into Internal Erosion

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 785
Author(s):  
Ahmed Ibrahim ◽  
Mohamed Meguid
Keyword(s):  
Experimental Data ◽  
Soil Water ◽  
Pore Water Pressure ◽  
Fluid Model ◽  
Water Pressure ◽  
Interaction Model ◽  
Internal Erosion ◽  
Wide Range ◽  
Particulate Soil ◽  
Soil And Water

Resolving the interaction between soil and water is critical to understanding a wide range of geotechnical applications. In cases when hydrodynamic forces are dominant and soil fluidization is expected, it is necessary to account for the microscale interactions between soil and water. Some of the existing models such as coupled Computational Fluid Dynamics–Discrete Element Method (CFD-DEM) can capture microscale interactions quite accurately. However, it is often computationally expensive and cannot be easily applied at a scale that would aid the design process. Contrastingly, continuum-based models such as the Two-Fluid Model (TFM) can be a computationally feasible and scalable alternative. In this study, we explored the potential of the TFM to simulate granular soil–water interactions. The model was validated by simulating the internal fluidization of a sand bed due to an upward water jet. Analogous to leakage from a pressurized pipe, the simulation was compared with the available experimental data to evaluate the model performance. The numerical results showed decent agreement with the experimental data in terms of excess pore water pressure, fluidization patterns, and physical deformations in violent flow regimes. Moreover, detailed soil characteristics such as particle size distribution could be implemented, which was previously considered a shortcoming of the model. Overall, the model’s performance indicates that TFM is a viable tool for the simulation of particulate soil–water mixtures.

scholarly journals Photochemical laws and visual phenomena

1946 ◽  
Vol 133 (870) ◽  
pp. 63-75 ◽  
Keyword(s):  
Experimental Data ◽  
Recovery Process ◽  
Visual Sensitivity ◽  
Rapid Recovery ◽  
Foveal Vision ◽  
Experimental Conditions ◽  
Reciprocity Law ◽  
Wide Range ◽  
Visual Phenomena ◽  
Nervous Transmission

By measuring the course of recovery of visual sensitivity in the dark, after exposure to light, it has been demonstrated that all the phenomena of recovery can be explained—qualitatively—by the known fundamental principles of photochemistry. In particular, the reciprocity law, which is widely valid in photographic processes, only holds under certain limited circumstances for visual phenomena. In the case of foveal vision the reciprocity law does not hold, owing to the rapid recovery process, except for very brief periods of exposure. In the case of parafoveal vision the recovery process for the scotopic mechanism is sufficiently slow to allow validity of the reciprocity law over a wide range of exposure periods, although the law still breaks down for the parafoveal photopic mechanism. This circumscribed validity of the reciprocity law is of practical service in that the effect of many experimental conditions can be predicted from a very limited set of suitably chosen experimental data. It may be noted that it has not been found necessary to introduce any postulate involving recovery of the nervous transmission system as part of the recovery process.

scholarly journals Experimental Measurement Of Soret Coefficient Of Binary Hydorcarbon Mixtures

2021 ◽  
Author(s):  
Md A. Rahman
Keyword(s):  
Experimental Data ◽  
Binary Mixtures ◽  
Diffusion Coefficients ◽  
Liquid Mixtures ◽  
Zehnder Interferometer ◽  
Soret Coefficient ◽  
Refractive Indices ◽  
Maximum Deviation ◽  
Wide Range ◽  
Mach Zehnder Interferometer

Measurement of diffusion coefficients is essential for simulation and prediction of oil reservoirs. Recently, a new experimental set-up has been built at Ryerson University to measure the transport coefficient of transparent liquid mixtures. Laser-based optical digital interferometry techniques using a Mach-Zehnder Interferometer have been used for measuring the diffusion coefficients. This method is non-intrusive, highly accurate, and can provide a detailed 2-D visualization of temperature and concentration fields. Five binary liquid mixtures of Decane (C10H22) - Isobutylbenzene (IBB), Decane (C10H22) - 1,2,3,4 Tetrahydronaphthalene (THN), Dodecane (C12H26) - Isobutylbenzene (IBB), Dodecane (C12H26) - 1,2,3,4 Tetrahydronaphthalene (THN) and Isobutylbenzene (IBB) - 1,2,3,4 Tetrahydronaphtha-lene (THN) have been selected. The mixtures have been prepared from pure C10H22, C12H26, IBB and THN for 50% mass fractions. These five binary mixtures are representatives of binary interactions between alkane, one-ring aromatic and two-ring aromatic hydrocarbons. The thermal designs of the diffusion cell, as well as the data analyze method, have been improved. A comparison of experimental data with theoretical analysis based on the Firoozabadi model for measuring thermodiffusion coefficient and Peng-Robinson equation of state (PR-EOS) for measuring the physical properties have been conducted. Experimental results showed a maximum deviation of less than 2% for IBB- C12H26 and THN-IBB and 9% for THN-C12H26 from the available benchmark results. Accurate knowledge of refractive index is highly relevant to correlations with concentration, temperature, wavelength and pressure in non-intrusive experiments carried out with transparent fluids. It can be used for the identification and characterization of pure materials and for the measurement of concentration of multi-component mixtures. In this current scope, refractive indices of five binary mixtures C10H22-IBB, C10H22-THN, C12H26-IBB, C12H26-THN and IBB-THN have been measured using both the Mach-Zehnder Interferometer and a multi-wavelength Abbemat refractometer. Temperature and concentration coefficients of refractive indices, or so-called contrast factors, as well as their individual correlation to calculate refractive indices have been presented for a wide range of visible spectrums such as 436 nm to 657 nm. Comparison with available literature and mixing rules shows that new correlations can predict the experimental data with deviations of less than 0.001.

Mechanical Behavior of FRP-Confined Rectangular Concrete Column

2010 ◽  
Vol 163-167 ◽  
pp. 3804-3807
Author(s):  
Ping Wu ◽  
Feng Yu
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Cross Section ◽  
Strain Softening ◽  
Axial Strain ◽  
Concrete Column ◽  
Stress Strain ◽  
Strain Relationship ◽  
Rectangular Concrete Column ◽  
Strain Model

According to the analysis of existing experimental data, it is well known that the behavior of FRP-confined rectangular concrete column were mainly related to the cross section coefficient of concrete, the confinement effect coefficient and the strength of concrete. Based on experimental study and theoretical analysis, the formula for bearing capacity and ultimate axial strain of FRP-confined rectangular concrete column were proposed, and the stress-strain model with strain-hardening components or strain-softening components. The effects of every parameter on the stress-strain relationship were carefully considered. The predictions of the model agree well with test data.

scholarly journals Growth analysis of Scots pine (Pinus sylvestris L.) seedlings cultivated in a wide range of experimental conditions

2014 ◽  
Vol 54 (3) ◽  
pp. 255-272 ◽  
Author(s):  
Włodzimierz Żelawski ◽  
Andrzej Łotocki ◽  
Helena Morteczka ◽  
Teresa Przykorska-Żelawska ◽  
Wincenty Wrrześniewski
Keyword(s):  
Experimental Data ◽  
Plant Growth ◽  
Scots Pine ◽  
Growth Analysis ◽  
Time Instant ◽  
Initial Value ◽  
Experimental Conditions ◽  
Pine Seedlings ◽  
Wide Range ◽  
Future Work

The work of this laboratory for many years with Scots pine seedlings has allowed to collect quite unique information as to the accumulation and distribution of dry matter and the reaction of plants to various environmental influences. It seems worthwhile to publish the main experimental data almost <em>in extenso</em> because they may be used in future work for building mathematical models of plant growth. The presented experimental data enabled to discuss controversial points of quantitative analysis of plant growth such as: the time instant and the initial value of growth to be taken as the starting points (t<sub>0</sub> W<sub>0</sub>); exponential approximation of the growth curve; inadequacy of allometric approach in modelling vegetative growth of plants, etc. The discussion aims at defining more closely the essential notions of growth analysis.

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