Behavior of Geocell-Reinforced Sand under a Vertical Load

2008 ◽  
Vol 2045 (1) ◽  
pp. 95-101 ◽  
Author(s):  
Jie Han ◽  
Xiaoming Yang ◽  
Dov Leshchinsky ◽  
Robert L. Parsons
Keyword(s):  
Bearing Capacity ◽  
Numerical Study ◽  
Three Dimensional ◽  
Numerical Results ◽  
Shear Stresses ◽  
Vertical Load ◽  
Reinforced Sand ◽  
Numerical Software ◽  
Load To Failure ◽  
Test Process

Geocells have a three-dimensional cellular structure, which can be used to stabilize foundations by increasing bearing capacity and reducing settlements. However, a considerable gap exists between the applications and the theories for the mechanisms of geocell-reinforced foundations. An experimental and numerical study on the behavior of geocell-reinforced sand under a vertical load is presented. A single geocell was filled with sand and subjected to a vertical load to failure. This test process was modeled by using the FLAC3D numerical software to investigate the mechanisms of geocell and sand interactions. Experimental and numerical results both demonstrated that the geocell increased the ultimate bearing capacity and the modulus of the sand. The numerical results include the distributions of displacements in the sand and geocell walls and the distributions of tensile stresses and shear stresses acting on the geocell walls. The numerical results for geocell-reinforced sand are compared to those for sand without geocell.

Fluid Flow and Lateral Fluid Dispersion in Bounded Granular Beds

2002 ◽  
Author(s):  
Azita Soleymani ◽  
Eveliina Takasuo ◽  
Piroz Zamankhan ◽  
William Polashenski
Keyword(s):  
Reynolds Number ◽  
Porous Media ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Numerical Study ◽  
Fluid Velocity ◽  
Three Dimensional ◽  
Numerical Results ◽  
Transition To Turbulence ◽  
Wide Range

Results are presented from a numerical study examining the flow of a viscous, incompressible fluid through random packing of nonoverlapping spheres at moderate Reynolds numbers (based on pore permeability and interstitial fluid velocity), spanning a wide range of flow conditions for porous media. By using a laminar model including inertial terms and assuming rough walls, numerical solutions of the Navier-Stokes equations in three-dimensional porous packed beds resulted in dimensionless pressure drops in excellent agreement with those reported in a previous study (Fand et al., 1987). This observation suggests that no transition to turbulence could occur in the range of Reynolds number studied. For flows in the Forchheimer regime, numerical results are presented of the lateral dispersivity of solute continuously injected into a three-dimensional bounded granular bed at moderate Peclet numbers. Lateral fluid dispersion coefficients are calculated by comparing the concentration profiles obtained from numerical and analytical methods. Comparing the present numerical results with data available in the literature, no evidence has been found to support the speculations by others for a transition from laminar to turbulent regimes in porous media at a critical Reynolds number.

scholarly journals Numerical and Experimental Study on Deficient Short Steel Tubes Strengthened with CFRP Under Compression

2019 ◽  
Author(s):  
Mohammad Reza Ghaemdoust ◽  
Omid Yousefi ◽  
Kambiz Narmashiri ◽  
Masoumeh Karimian
Keyword(s):  
Bearing Capacity ◽  
Numerical Study ◽  
Three Dimensional ◽  
Local Buckling ◽  
Steel Tubes ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Steel Columns ◽  
Repair Costs ◽  
The Impact

In view of development and repair costs, support of structures is imperative. Several factors, for example, design and calculation errors, absence of appropriate installation, change of structures application, exhaustion, seismic tremor, fire and natural conditions diminish their strength. In such cases, structures have need of rehabilitation and restoration to achieve their original performance. One of the most up to date materials for retrofitting is carbon fiber reinforced polymer (CFRP) that can provide an amount of restriction to postpone buckling of thin steel walls. This paper provides a numerical and experimental investigation on CFRP strengthened short steel tubes with initial horizontal and vertical deficiency under compression. Ten square and circular specimens were tested to study effects of the following parameters: (1) position of deficiency, horizontal or vertical; (2) tube shape, square or circular; (3) CFRP strengthening. In the experiments, axial static loading was gradually applied and for the numerical study three-dimensional (3D) static nonlinear analysis method using ABAQUS software was performed. The results show that deficiency reduces load-bearing capacity of steel columns and the impact of horizontal deficiency is higher than the impact of vertical deficiency, in both square and circular tubes. Use of CFRP materials for strengthening of short steel columns with initial deficiency indicates that fibers play a considerable role on increasing load bearing capacity, reducing stress at the damage location, preventing deformation caused by deficiency and delaying local buckling. Both numerical and experimental outcomes are in good agreement, which underlines the accuracy of the models adopted.

scholarly journals Three-dimensional numerical study of thermal exchanges in different geometry sections of mini-channels using three different nanoparticles

10.30544/455 ◽  
2020 ◽  
Vol 26 (1) ◽  
pp. 103-119
Author(s):  
Kamel Chadi ◽  
Nourredine Belghar ◽  
Belhi Guerira ◽  
Aissam Messaoudi
Keyword(s):  
Reynolds Number ◽  
Volume Fraction ◽  
Numerical Study ◽  
Three Dimensional ◽  
Numerical Results ◽  
Junction Temperature ◽  
Ansys Fluent ◽  
Cooling Fluid ◽  
Mini Channels ◽  
Exchange Surface

In the present work, we have studied the thermal exchanges of different geometry sections of mini-channels of a cooler numerically. Particularly, we have chosen a mini channels cooler copper for cooling an electronic chip IGBT. In our simulation of three-dimensional (3D), we have compared the numerical results for the different forms of the proposed mini-channels and the three different types of nano-fluids by using the Cu-water, the Ag-water, and the Diamond-water with a volume fraction of 0.02%. The numerical results are obtained by choosing a Reynolds number (Re) between 100 and 900 and considering that the flow regime is stationary. The simulation was performed using commercial software, ANSYS-Fluent 15.0. The results obtained show that the increase of the exchange surface between the walls of the mini channels and the cooling fluid makes increases the heat exchange coefficient and the improvement of the maximum junction temperature of the electronic chip IGBT with the increase of the Reynolds number. The choice of nanoparticles has considerable effects on improving the heat transfer and the maximum junction temperature of the chip IGBT.

scholarly journals Behavior of Foundations on Reinforced Sabkha Soil: A Numerical Study

2020 ◽  
pp. 15-23
Author(s):  
Lamia Sadek ◽  
Khaled M. M. Bahloul
Keyword(s):  
Finite Element ◽  
Computer Program ◽  
Bearing Capacity ◽  
Numerical Study ◽  
Sand Layer ◽  
Fiber Reinforced ◽  
Reinforced Sand ◽  
Strip Footings

The aim of this research is to investigate numerically the behavior of strip footings resting on Sabkha soil reinforced using two methods. Firstly, using a layer of compacted sand reinforced with random distributed fibers beneath footing. Secondly, using a layer of compacted sand reinforced with geogrids. The benefit of mentioned two methods on the improvement of strip footings bearing capacity and decreasing the settlement was investigated using a finite element computer program Plaxis 2D ver. 8.6. It was found that using two methods increases bearing capacity of strip footings significantly specially using first method (fiber reinforced sand layer). It was observed also that the settlement decreased for the same stress values.

Numerical Study of Nozzle Design on Cadmium Quenching Process in Thermochemical Splitting of Water

2009 ◽  
Author(s):  
Jianhu Nie ◽  
Yitung Chen ◽  
Bunsen Wong ◽  
Lloyd C. Brown
Keyword(s):  
Heat Transfer ◽  
Hydrogen Production ◽  
Gas Flow ◽  
Numerical Study ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Numerical Results ◽  
Nozzle Design ◽  
Flow And Heat Transfer ◽  
Quenching Process

Three-dimensional liquid-gas flow with condensation during cadmium quenching process for hydrogen production was numerically simulated in order to effectively guide the design of solar decomposer and vapor quencher. The mixture model was selected for modeling the multiphase flow, and the two-equation RNG k-ε model was used to model the turbulent flow and heat transfer. Numerical results including velocity, temperature, pressure, and mole fraction distributions were obtained for different nozzle designs. Numerical results showed that flow is relatively low in the decomposer and close to the bottom and the top inlets. The maximum velocity develops in the region near the entrance of the quenching nozzle as the nozzle angle is small. As the nozzle angle is large, the maximum velocity appears in the exit tube. Temperature, pressure and cadmium vapor distributions are also directly affected by the nozzle angle.

2D and 3D Multiscale Computational Modeling of Dynamic Microorgan Devices as Drug Screening Platforms

2015 ◽  
Author(s):  
Filippos Tourlomousis ◽  
Robert C. Chang
Keyword(s):  
Large Scale ◽  
Numerical Study ◽  
Numerical Results ◽  
Scale Model ◽  
Small Scale ◽  
Optimum Process ◽  
Shear Stresses ◽  
Enzymatic Reactions ◽  
Modeling Approach

The ability to incorporate three-dimensional (3D) hepatocyte-laden hydrogel constructs using layered fabrication approaches into devices that can be perfused with drugs enables the creation of dynamic microorgan devices (DMDs) that offer an optimal analog of the in vivo liver metabolism scenario. The dynamic nature of such in vitro metabolism models demands reliable numerical tools to determine the optimum process, material, and geometric parameters for the most effective metabolic conversion of the perfused drug into the liver microenvironment. However, there is a current lack of literature that integrates computational approaches to guide the optimum design of such devices. The groundwork of the present numerical study has been laid by our previous study [1], where the authors modeled in 2D an in vitro DMD of arbitrary dimensions and identified the modeling challenges towards meaningful results. These constructs are hosted in the chamber of the microfluidic device serving as walls of the microfluidic array of channels through which a fluorescent drug substrate is perfused into the microfluidic printed channel walls at a specified volumetric flow rate assuring Stokes flow conditions (Re<<1). Due to the porous nature of the hydrogel walls, a metabolized drug product is collected at the outlet port. A rigorous FEM based modeling approach is presented for a single channel parallel model geometry (1 free flow channel with 2 porous walls), where the hydrodynamics, mass transfer and pharmacokinetics equations are solved numerically in order to yield the drug metabolite concentration profile at the DMD outlet. The fluid induces shear stresses are assessed both in 3D, with only 27 cells modeled as single compartment voids, where all of the enzymatic reactions are assumed to take place. In this way, the mechanotransduction effect that alters the hepatocyte metabolic activity is assessed for a small scale model. This approach overcomes the numerical limitations imposed by the cell density (∼1012 cells/m3) of the large scale DMD device. In addition, a compartmentalization technique is proposed in order to assess the metabolism process at the subcellular level. The numerical results are validated with experiments to reveal the robustness of the proposed modeling approach and the necessity of scaling the numerical results by preserving dynamic and biochemical similarity between the small and large scale model.

scholarly journals A numerical study of strained three-dimensional wall-bounded turbulence

2000 ◽  
Vol 416 ◽  
pp. 75-116 ◽  
Author(s):  
G. N. COLEMAN ◽  
J. KIM ◽  
P. R. SPALART
Keyword(s):  
Pressure Gradient ◽  
Boundary Layers ◽  
Numerical Study ◽  
Three Dimensional ◽  
Adverse Pressure Gradient ◽  
Model Testing ◽  
Turbulent Shear ◽  
Shear Stresses ◽  
Dimensional Boundary ◽  
The Mean

Channel flow, initially fully developed and two-dimensional, is subjected to mean strains that emulate the effect of rapid changes of streamwise and spanwise pressure gradients in three-dimensional boundary layers, ducts, or diffusers. As in previous studies of homogeneous turbulence, this is done by deforming the domain of a direct numerical simulation (DNS); here however the domain is periodic in only two directions and contains parallel walls. The velocity difference between the inner and outer layers is controlled by accelerating the channel walls in their own plane, as in earlier studies of three-dimensional channel flows. By simultaneously moving the walls and straining the domain we duplicate both the inner and outer regions of the spatially developing case. The results are used to address basic physics and modelling issues. Flows subject to impulsive mean three-dimensionality with and without the mean deceleration of an adverse pressure gradient (APG) are considered: strains imitating swept-wing and pure skewing (sideways turning) three-dimensional boundary layers are imposed. The APG influences the structure of the turbulence, measured for example by the ratio of shear stress to kinetic energy, much more than does the pure skewing. For both deformations, the evolution of the Reynolds stress is profoundly affected by changes to the velocity–pressure-gradient correlation Πij. This term – which represents the finite time required for the mean strain to modify the shape and orientation of the turbulent motions – is primarily responsible for the difference (lag) in direction between the mean shear and the turbulent shear stresses, a well-known feature of perturbed three-dimensional boundary layers. Files containing the DNS database and model-testing software are available from the authors for distribution, as tools for future closure-model testing.

Experimental and Numerical Study of Evaporating Flow Heat Transfer in Micro-Channel

2007 ◽  
Author(s):  
HoKi Lee ◽  
C. D. Richards ◽  
R. F. Richards
Keyword(s):  
Heat Transfer ◽  
Latent Heat ◽  
Numerical Study ◽  
Three Dimensional ◽  
Contact Angles ◽  
Numerical Results ◽  
Working Fluid ◽  
Micro Channels ◽  
Flow Heat ◽  
Domain Integration

Experimental and numerical results are presented for steady evaporating flow heat transfer from open top square micro-channels. Radial channels, 40 microns high, and 35, 50 and 70 microns wide with 5 micron wide SU-8 walls are considered. The channels are filled with Fluorinert FC77 working fluid pumped by capillary forces from a reservoir at the outer circumference of the radial channels. An energy balance on the radial channels including heat into the channels, conduction heat transfer radially along the channels and latent heat transfer via evaporation of the working fluid from the channels is experimentally determined. Microphotography is used to visualize the working fluid and the meniscus contact angles in the channels. A three-dimensional finite difference time-domain integration is used to predict sensible heat transfer rates and latent heat transfer/ evaporation rates. Experimental measurements are compared to the numerical results to extract estimates of the liquid thickness in the channels.

Numerical Study on Three-Dimensional Wall Effects of Flat Micro Nozzle

2011 ◽  
Vol 339 ◽  
pp. 276-282
Author(s):  
Jun Jie Tong ◽  
Ji Wen Cen ◽  
Jin Liang Xu
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Numerical Results ◽  
Two Dimensional ◽  
Wall Effects ◽  
Micro Nozzle

The FLUENT6.1 software is applied to simulate the supersonic flow in micro convergent-divergent nozzle which is fabricated from flat silicon wafers. The simulation is complemented by parallel computing steady 2-D and 3-D Navier-stokes equations to study the three-dimensional wall effects on temperature and velocity inside the micro nozzle. Also the performances of fluent mass coefficients and thrust force efficiencies are studied. It is observed by the study that three-dimensional wall effects are not negligible in flat micro nozzle. The velocity of fluid in three-dimensional nozzle is less than the corresponding velocity of fluid in two-dimensional nozzle significantly, while the temperature of fluid in three-dimensional nozzle is much higher than the corresponding temperature of fluid in two-dimensional nozzle. The mass flow rate and thrust at the exit of 2-D nozzle are greater than the corresponding mass flow rate and thrust at the exit of three-dimensional. With the throat Renaults being increased, the corresponding differences between two-dimensional numerical results and three-dimensional numerical results decreased accordingly. Two-dimensional numerical results can not correctly predict the actual mass flow rate and thrust at the exit of micro nozzle.

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