scholarly journals Simulation of three-dimensional rapid free-surface granular flow past different types of obstructions using the SPH method

2016 ◽  
Vol 62 (232) ◽  
pp. 335-347 ◽  
Author(s):  
AHMED M. ABDELRAZEK ◽  
ICHIRO KIMURA ◽  
YASUYUKI SHIMIZU
Keyword(s):  
Granular Flow ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Material Behavior ◽  
Sph Method ◽  
Perfectly Plastic ◽  
Depth Direction ◽  
Aspect Ratios ◽  
Flow Past ◽  
Different Types

ABSTRACTIn nature, when hazardous geophysical granular flows (e.g. a snow avalanche) impact on an obstacle as they stream down a slope, rapid changes in flow depth, direction and velocity will occur. It is important to understand how granular material flows around such obstacles in order to enhance the design of defense structures. In this study, a three dimensional (3-D) Smoothed Particle Hydrodynamics (SPH) model is developed to simulate granular flow past different types of obstacles. The elastic–perfectly plastic model with implementation of the Mohr–Coulomb failure criterion is applied to simulate the material behavior, which describes the stress states of soil in the plastic flow regime. The model was validated by simulating the collapse of a 3-D column of sand with two different aspect ratios; the results showed that the SPH method is capable of simulating granular flow. The model is then applied to simulate the gravity-driven granular flow down an inclined surface obstructed by a group of columns with different spacing, a circular cylinder and a tetrahedral wedge. The numerical results are then compared with experimental results and two different numerical solutions. The good agreements obtained from these comparisons demonstrate that the SPH method may be a powerful method for simulating granular flow and can be extended to design protective structures.

Three-dimensional instabilities in oscillatory flow past elliptic cylinders

2016 ◽  
Vol 798 ◽  
pp. 371-397 ◽  
Author(s):  
José P. Gallardo ◽  
Helge I. Andersson ◽  
Bjørnar Pettersen
Keyword(s):  
Circular Cylinder ◽  
Flow Direction ◽  
Three Dimensional ◽  
Circular Cylinders ◽  
Flow Structures ◽  
Three Dimensional Flow ◽  
Elliptical Cross ◽  
Dimensional Flow ◽  
Aspect Ratios ◽  
Flow Past

We investigate the early development of instabilities in the oscillatory viscous flow past cylinders with elliptic cross-sections using three-dimensional direct numerical simulations. This is a classical hydrodynamic problem for circular cylinders, but other configurations have received only marginal attention. Computed results for some different aspect ratios ${\it\Lambda}$ from 1 : 1 to 1 : 3, all with the major axis of the ellipse aligned in the main flow direction, show good qualitative agreement with Hall’s stability theory (J. Fluid Mech., vol. 146, 1984, pp. 347–367), which predicts a cusp-shaped curve for the onset of the primary instability. The three-dimensional flow structures for aspect ratios larger than 2 : 3 resemble those of a circular cylinder, whereas the elliptical cross-section with the lowest aspect ratio of 1 : 3 exhibits oblate rather than tubular three-dimensional flow structures as well as a pair of counter-rotating spanwise vortices which emerges near the tips of the ellipse. Contrary to a circular cylinder, instabilities for an elliptic cylinder with sufficiently high eccentricity emerge from four rather than two different locations in accordance with the Hall theory.

scholarly journals Supercomputer model of dynamical dusty gas with intense momentum transfer between phases based on OpenFPM library

2021 ◽  
Vol 2099 (1) ◽  
pp. 012056
Author(s):  
Vitaliy Grigoryev ◽  
Olga Stoyanovskaya ◽  
Nikolay Snytnikov
Keyword(s):  
Continuous Medium ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Point Explosion ◽  
Vector Data ◽  
Sph Method ◽  
One Dimensional ◽  
Gas Dynamic ◽  
Plane Sound ◽  
Gas Dynamic Equations

Abstract The paper considers the solution of model gas-dynamic problems (propagation of plane sound wave, one-dimensional shock tube problem, three-dimensional problem of a point explosion in a continuous medium) in the case of a gas-dust medium. The interaction of dust and gas was taken into account using the IDIC method within the SPH method used to solve gas-dynamic equations. An important feature of the work is the use of the open computational package OpenFPM, which makes it easy to carry out parallel computations. The main advantage of this package is the ready-made (implemented by the authors of the package) and intuitive, automatically parallelizable vector data structures, the use of which is identical both in the case of calculations on a personal computer and in the case of using supercomputer resources. The paper analyzes the efficiency of parallelization of numerical solutions of the considered problems.

Numerical Study on Added Resistance Computations in Short Waves

2016 ◽  
Author(s):  
Xinshu Zhang ◽  
Kang Tian ◽  
Yunxiang You
Keyword(s):  
Experimental Data ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Three Dimensional ◽  
Added Resistance ◽  
Rankine Panel Method ◽  
Short Waves ◽  
Global Performance ◽  
Different Types ◽  
Wigley Hull

Evaluation of added resistance in short waves is critical to the assessment of the global performance of a ship traveling in a seaway. In this paper, three methods of added resistance evaluation in short waves are briefly reviewed, including those proposed by Fujii & Takahashi [1], Faltinsen et al. [2], and Kuroda et al. [3]. Based on the experimental data collected by Kuroda et al., a new method is developed for the estimation of added resistance in short waves. The proposed method is validated by comparing the obtained numerical results with experimental data and other numerical solutions for different types of hulls, including the Wigley hull I, KVLCC2 hull, Series 60 hull with CB = 0.7, and the S-175 hull. The present study confirms that the developed method can well predict the added resistance in short waves and complement the three-dimensional Rankine panel method developed in a previous study focusing on intermediate and long waves.

Three-dimensional static analysis of rectangular thick plates by using the meshless local Petrov—Galerkin method

2009 ◽  
Vol 223 (9) ◽  
pp. 1983-1996 ◽  
Author(s):  
R Vaghefi ◽  
G H Baradaran ◽  
H Koohkan
Keyword(s):  
Boundary Conditions ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
3D Analysis ◽  
Rectangular Plates ◽  
Weak Formulation ◽  
Heaviside Step Function ◽  
Thick Plates ◽  
Test Function ◽  
Aspect Ratios

In this article, a meshless local Petrov—Galerkin (MLPG) approach is developed for three-dimensional (3D) analysis of thick plates. Two different MLPG methods including MLPG1 and MLPG5 are employed to solve the elasto-static problems of thick plates. In MLPG1, a namely fourth-order spline function is considered as test function, while the Heaviside step function is employed as test function in MLPG5. Considering 3D equilibrium equations, the local symmetric weak forms are derived. The moving least-squares approximation is used to interpolate the solution variables and the penalty method is applied to impose the essential boundary conditions. In the present study, brick-shaped domains are chosen as local subdomains and support domains. The integrals appearing in the weak formulation are easily evaluated over brick-shaped subdomains and their boundaries. Considering the present approach, elasto-static deformations and stresses are analysed for thick rectangular plates with various boundary conditions and different aspect ratios. Excellent agreement is seen comparing the present results with the known analytical and numerical solutions in the literature.

Analytical Piezoelasticity Solution for Natural Frequencies of Levy-Type Piezolaminated Plates

2019 ◽  
Vol 11 (03) ◽  
pp. 1950023 ◽  
Author(s):  
Susanta Behera ◽  
Poonam Kumari
Keyword(s):  
Natural Frequencies ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Single Layer ◽  
Free Vibration Analysis ◽  
Mode Shapes ◽  
Kantorovich Method ◽  
Extended Kantorovich Method ◽  
Aspect Ratios ◽  
Support Conditions

First time, an analytical solution based on three-dimensional (3D) piezoelasticity is developed for the free vibration analysis of Levy-type piezolaminated plates using 3D extended Kantorovich method (EKM). Extended Hamilton principle (which is extended from elastic to piezoelectric case) is further extended to the dynamic version of mixed form containing contributions from the electrical terms. Multi-term multi-field extended Kantorovich method in conjunction with Fourier series (along [Formula: see text]-direction) is employed to obtain two sets of first-order homogeneous ordinary differential equations (8[Formula: see text] along [Formula: see text]- and [Formula: see text]-axes). A robust algorithm is designed (Fortran Code) to extract the natural frequencies and mode shapes of Levy-type piezolaminated plates. The accuracy and efficacy of this technique are verified thoroughly by comparing it with the existing results in the literature and with the 3D finite element (FE) solutions. Numerical results are presented for single-layer piezoelectric and smart sandwich plates considering five different boundary support conditions, three aspect ratios (length to thickness ratio) and electric open and close circuit conditions. The present results shall be used as a benchmark to assess various two-dimensional (2D) and 3D numerical solutions (e.g., FEM, DQM, etc.).

Three-Dimensional Analysis of Ice Sheet Indentation: Limit Analysis Solutions

1989 ◽  
Vol 111 (1) ◽  
pp. 63-69 ◽  
Author(s):  
D. G. Karr ◽  
J. C. Watson ◽  
M. HooFatt
Keyword(s):  
Upper Bound ◽  
Limit Analysis ◽  
Plastic Material ◽  
Yield Criterion ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Upper Bound Theorem ◽  
Infinite Layer ◽  
Perfectly Plastic ◽  
Aspect Ratios

A method is presented for determining the collapse pressures of an ice sheet subjected to a uniformly distributed edge load by applying the upper-bound theorem of limit analysis. The ice sheet is idealized as a semi-infinite layer of elastic-perfectly plastic material. A quadratic anisotropic yield criterion is used to calculate the indentation pressures. The ice sheet consists of columnar ice and is assumed isotropic in the plane of the ice sheet. Upper-bound solutions are found by optimizing a three-dimensional discontinuous velocity field representing an assumed collapse pattern of the ice sheet. Solutions are based on various ratios of indentor width to ice thickness, thereby providing an envelope of indentation pressures over a range of aspect ratios, from conditions of plane strain to plane stress. Solutions are then compared with corresponding two and three-dimensional lower-bound analyses.

An Analytical Framework for the Solution of Autofrettaged Tubes Under Constant Axial Strain Condition

2008 ◽  
Author(s):  
E. Hosseinian ◽  
G. H. Farrahi ◽  
M. R. Movahhedy
Keyword(s):  
Numerical Methods ◽  
Analytical Method ◽  
Numerical Solutions ◽  
Yield Criterion ◽  
Axial Strain ◽  
Material Model ◽  
Analytical Framework ◽  
Material Behavior ◽  
Perfectly Plastic ◽  
Special Cases

Autofrettage is a technique for introducing beneficial residual stresses into cylinders. Both analytical and numerical methods are used for analysis of the autofrettage process. Analytical methods have been presented only for special cases of autofrettage. In this work, an analytical framework for the solution of autofrettaged tubes with constant axial strain conditions is developed. Material behavior is assumed to be incompressible and two different quadratic polynomials are used for strain hardening in loading and unloading. Clearly, elastic-perfectly plastic and linear hardening materials are special cases of this general model. This material model is convenient for description of the behavior of a class of pressure vessel steels such as A723. The Bauschinger effect is assumed fixed and total deformation theory based upon von-Mises yield criterion is used. An explicit solution for the constant axial strain conditions and its special cases such as plane strain and closed-end conditions is obtained. For open-end condition for which axial force is zero the presented analytical method leads to a simple numerical solution. Finally, results of the new method are compared with those obtained from other analytical and numerical methods and excellent agreement is observed. Since the presented method is a general analytical method, it is believed that it could be used for validation of numerical solutions or analytical solutions for special loading cases.

An Experimental Study of Flow Past a Dual Step Cylinder

2010 ◽  
Author(s):  
Chris R. Morton ◽  
Serhiy Yarusevych
Keyword(s):  
Flow Visualization ◽  
Vortex Shedding ◽  
Large Diameter ◽  
Three Dimensional ◽  
Small Diameter ◽  
Single Vortex ◽  
Aspect Ratios ◽  
Flow Past ◽  
Large Cylinder ◽  
Small Cylinder

Flow past a dual step cylinder has been investigated using experimental flow visualization methods. The dual step cylinder model is comprised of a small diameter cylinder (d) and a large diameter cylinder (D) mounted at the mid-span of the small cylinder. The experiments have been performed for ReD = 1050, D/d = 2, and a range of large cylinder aspect ratios (L/D). The focus of the study is on vortex shedding and vortex interactions occurring in the large and small cylinder wakes. A flow visualization study completed using hydrogen bubble technique and planar laser induced fluorescence has shown that the flow development is highly dependent on the aspect ratio of the large cylinder, L/D. The results identify four distinct flow regimes: (i) for L/D ≥ 17, three vortex shedding cells form in the wake of the large cylinder, one central cell and two cells of lower frequency extending over about 4.5D from the large cylinder ends, (ii) for 7 < L/D ≤ 14, a single vortex shedding cell forms in the wake of the large cylinder, whose shedding frequency decreases with decreasing L/D, (iii) for 2 ≤ L/D ≤ 7, vortex shedding in the wake of the large cylinder is highly three-dimensional, such that each vortex deforms while it is shed into the wake, (iv) for 0.2 ≤ L/D ≤ 1, only small cylinder vortices are shed in the wake and often form vortex connections across the wake of the large cylinder.

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