scholarly journals Numerical Investigation of Sloshing in Rectangular Tank with Permeable Baffle

2020 ◽  
Vol 8 (9) ◽  
pp. 671
Author(s):  
Liting Yu ◽  
Mi-An Xue ◽  
Aimeng Zhu
Keyword(s):  
Permeability Coefficient ◽  
Structural Damage ◽  
Maximum Flow ◽  
Arbitrary Lagrangian Eulerian ◽  
The Finite Element Method ◽  
Resonant Frequencies ◽  
Cargo Transport ◽  
Violent Sloshing ◽  
Theoretical Results ◽  
Flow Velocities

Violent sloshing induced by excitation with large amplitudes or resonant frequencies may result in structural damage of the liquid-tank or even the overturning of the liquid cargo transport system. Therefore, impermeable and permeable vertical baffles were investigated numerically to suppress sloshing. The numerical simulations were based on the finite element method and arbitrary Lagrangian–Eulerian (ALE) method. The numerical model was verified by the available experimental data, numerical results and linear theoretical results. Based on the study of the effects of impermeable baffle height, amplitude and frequency of excitation on sloshing, the effects of baffle permeability on sloshing were investigated. Importantly, a critical permeability coefficient that was most effective to suppress sloshing was found. In addition, the maximum flow velocities in the tank with a baffle of small permeability coefficient were smaller than those in the tank with an impermeable baffle. While, the maximum flow velocities under a baffle of large permeability coefficient were larger than those in the tank with an impermeable baffle. Vortices were observed in the whole region of the baffle, tank bottom, tank walls and the free surface in the tank with a permeable baffle.

Continuous Roll Forming Simulation Using Arbitrary Lagrangian Eulerian Formalism

2011 ◽  
Vol 473 ◽  
pp. 564-571 ◽  
Author(s):  
Romain Boman ◽  
Jean Philippe Ponthot
Keyword(s):  
Numerical Simulation ◽  
Rolling Direction ◽  
Initial Guess ◽  
Roll Forming ◽  
Arbitrary Lagrangian Eulerian ◽  
The Finite Element Method ◽  
Forming Simulation ◽  
Element Size ◽  
Cold Roll ◽  
Classical Lagrangian

Due to the length of the mill, accurate modelling of stationary solution of continuous cold roll forming by the finite element method using the classical Lagrangian formulation usually requires a very large mesh leading to huge CPU times. In order to model industrial forming lines including many tools in a reasonable time, the sheet has to be shortened or the element size has to be increased leading to inaccurate results. On top of this, applying loads and boundary conditions on this smaller sheet is usually more difficult than in the continuous case. Moreover, transient dynamic vibrations, which are unnecessarily computed, may appear when the sheet hits each tool, decreasing the convergence rate of the numerical simulation. Beside this classical Lagrangian approach, an alternative method is given by the Arbitrary Lagrangian Eulerian (ALE) formalism which consists in decoupling the motion of the material and the mesh. Starting from an initial guess of the sheet geometry between the rolls, the numerical simulation is performed until the stationary state is reached with a mesh, the nodes of which are fixed in the rolling direction but are free to move on perpendicular plane, following the geometrical boundary of the sheet. The whole forming line can then be modelled using a limited number of brick and contact elements because the mesh is only refined near the tools where bending and contact occur. In this paper, ALE results are compared to previous Lagrangian simulations and experimental measurement on a U-channel, including springback. Advantages of the ALE method are finally demonstrated by the simulation of a tubular rocker panel on a 16-stands forming mill.

The Convergence of the H-P Version of the Finite Element Method with Quasi-Uniform Meshes for Three Dimensional Poisson Problems with Edge Singularity

2014 ◽  
Vol 644-650 ◽  
pp. 1551-1555
Author(s):  
Jian Ming Zhang ◽  
Yong He
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Weighted Sobolev Spaces ◽  
Three Dimensional ◽  
The Finite Element Method ◽  
Smooth Functions ◽  
Edge Singularity ◽  
Theoretical Predictions ◽  
Theoretical Results ◽  
Element Method

This paper is concerned with the convergence of the h-p version of the finite element method for three dimensional Poisson problems with edge singularity on quasi-uniform meshes. First, we present the theoretical results for the convergence of the h-p version of the finite element method with quasi-uniform meshes for elliptic problems on polyhedral domains on smooth functions in the framework of Jacobi-weighted Sobolev spaces. Second, we investigate and analyze numerical results for three dimensional Poission problems with edge singularity. Finally, we verified the theoretical predictions by the numerical computation.

The Effects of Compression and Pore Size Variations on the Liquid Flow Characteristics in Metal Foams

2001 ◽  
Vol 124 (1) ◽  
pp. 263-272 ◽  
Author(s):  
K. Boomsma ◽  
D. Poulikakos
Keyword(s):  
Flow Characteristics ◽  
Maximum Flow ◽  
Metal Foams ◽  
Heat Sinks ◽  
Convection Heat ◽  
Hydraulic Characteristics ◽  
Aluminum Foams ◽  
Transitional Regime ◽  
Open Cell ◽  
Flow Velocities

Open-cell aluminum foams were investigated using water to determine their hydraulic characteristics. Maximum fluid flow velocities achieved were 1.042 m/s. The permeability and form coefficient varied from 2.46×10−10 m2 and 8701 m−1 to 3529×10−10 m2 and 120 m−1, respectively. It was determined that the flowrate range influenced these calculated parameters, especially in the transitional regime where the permeability based Reynolds number varied between unity and 26.5. Beyond the transition regime where ReK≳30, the permeability and form coefficient monotonically approached values which were reported as being calculated at the maximum flow velocities attained. The results obtained in this study are relevant to engineering applications employing metal foams ranging from convection heat sinks to filters and flow straightening devices.

Alternative Mesh Refinement Methods for Analysing Soil Penetration Problems

2016 ◽  
Vol 846 ◽  
pp. 415-420
Author(s):  
M.H. Moavenian ◽  
Majidreza Nazem ◽  
John Phillip Carter
Keyword(s):  
Soil Layer ◽  
Deformation Analysis ◽  
Deep Penetration ◽  
Arbitrary Lagrangian Eulerian ◽  
The Finite Element Method ◽  
Mesh Distortion ◽  
B Splines ◽  
Arbitrary Lagrangian Eulerian Method ◽  
Complex Boundary ◽  
Free Falling

Despite recent advances in the finite element method, mesh distortion due to large deformations may still occur in some problems such as footings subjected to deep penetration or objects penetrating into a soil layer. In order to overcome mesh distortion, robust remeshing techniques are required. In this paper the performance of four remeshing methods is studied by analysing a free falling penetrometer penetrating into an undrained layer of soil. These techniques are implemented within the framework of the Arbitrary Lagrangian-Eulerian method and include the refinement based on an elastic relocation, a technique based on the Radial Basis Functions, the Spring Analogy method, and the Elastic Hardening method. Since one of the challenging problems in a large deformation analysis is dealing with complex boundary shapes, a scheme based on the B-Splines used in isogeometric analysis is also presented here.

scholarly journals Assessing Structural Damage after a Severe Wildfire: A Case Study

Buildings ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 171
Author(s):  
Angeliki Papalou ◽  
Dimitrios K. Baros
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Temperature Distribution ◽  
Structural Damage ◽  
Extreme Heat ◽  
The Finite Element Method ◽  
Residential Areas ◽  
Severe Damage ◽  
Construction Type

Wildfires have always been a threat to forests and areas of high combustible vegetation. When they are not kept under control, they can spread to residential areas, creating severe damage and destruction. This paper examines the effects of the extreme heat conditions that developed during a wildfire on buildings as a function of their construction type. One of the deadliest wildfires in Greece (July 2018) is considered as a case study, and the damage that occurred to buildings during this event is presented. The temperature of the various structural subsystems in extreme heat conditions was estimated using the finite element method. Parameters that influenced the corresponding temperature distribution were identified. Simple guidelines are given to prevent or reduce damage in buildings exposed to wildfires.

Comparative study of transcranial color duplex sonography and transcranial Doppler sonography in adults

1993 ◽  
Vol 78 (5) ◽  
pp. 776-784 ◽  
Author(s):  
Martin Schöoning ◽  
Reiner Buchholz ◽  
Jochen Walter
Keyword(s):  
Flow Velocity ◽  
Doppler Sonography ◽  
Transcranial Doppler Sonography ◽  
Maximum Flow ◽  
Duplex Sonography ◽  
Color Duplex Sonography ◽  
Content Type ◽  
Maximum Flow Velocity ◽  
Fine Print ◽  
Flow Velocities

✓ To determine whether the frequency shift recorded in basal cerebral arteries corresponds to “true” flow velocities, a prospective comparative study of transcranial color duplex sonography (TCCD) and transcranial Doppler sonography (TCD) was performed. A 2.0-MHz transducer of a computerized TCCD system and a TCD device were used. The middle cerebral artery (MCA) and anterior cerebral artery (ACA) were examined by TCCD in 49 healthy volunteers (mean age 35 ± 12 years). In 45 of the same volunteers a comparative TCD examination was possible. The studies were carried out blindly by different examiners at separate appointments. Peak systolic flow velocity, end-diastolic maximum flow velocity, time-averaged maximum flow velocity, and the pulsatility index were measured by both techniques. Additionally, for TCCD, time-averaged flow velocity was assessed, the resistance index and a spectral broadening index were calculated, and the energy output required for reliable measurement was analyzed. The TCCD signals were recorded in 98% of both MCA's and ACA's; with TCD, signals were recorded in 98% of MCA's and 87% of ACA's. Although in both vessels the angle-corrected peak systolic and time-averaged maximum velocities were approximately 10% to 15% higher in TCCD than in TCD measurements, correlation of flow velocities between both techniques was significant (p < 0.0001); differences between sides and age-dependency of flow velocities corresponded as well. In a reproducibility study, TCCD was repeated in 27 subjects by a third examiner with significant correlation (p < 0.0001) of both TCCD examinations. It is concluded that the advantage of TCCD is associated more with a qualitative aspect than a quantitative one. The additional visual dimension of TCCD can open new diagnostic possibilities in cerebrovascular disorders.

Dynamic Analysis and Design of Compliant Mechanisms Using the Finite Element Method

2012 ◽  
Vol 163 ◽  
pp. 111-115 ◽  
Author(s):  
Wen Jing Wang ◽  
Li Ge Zhang ◽  
Shu Sheng Bi
Keyword(s):  
Finite Element Method ◽  
Dynamic Model ◽  
Natural Frequency ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
The Finite Element Method ◽  
Dynamic Effects ◽  
Experiment System ◽  
Analysis And Design ◽  
Theoretical Results

Compliant mechanisms gain at least some of their mobility from the deflection of flexible members rather than from movable joints only. Dynamic effects are very important to improving the design of compliant mechanisms. An investigation on the dynamics and synthesis of the compliant mechanisms is presented. The dynamic model of compliant mechanisms is developed at first. The natural frequency and sensitivity are then studied based on the dynamic model. Finally, optimal design of compliant mechanism is investigated. The experimental study of natural frequency is performed. The comparison between the experiment results and the theoretical results verifies the validity of the experiment system and theoretical model.

Numerical Study of a 3-Axis Stage for Application of Fast Tool Servo

2014 ◽  
Vol 625 ◽  
pp. 219-223 ◽  
Author(s):  
Yung Tien Liu ◽  
Bo Jheng Li
Keyword(s):  
Numerical Study ◽  
Fast Response ◽  
Maximum Deviation ◽  
Stress And Strain ◽  
Fast Tool Servo ◽  
The Finite Element Method ◽  
Resonant Frequencies ◽  
Calculation Results ◽  
Flexural Hinges ◽  
Maximum Stresses

In this paper, a 3-axis stage consisted of a XY stage and Z-axis feeding tool holder is proposed for the application of fast tool servo (FTS). The XY stage actuated by six piezoelectric (PZT) actuators is designed with symmetric flexural hinges featuring low interference motions, high stiffness, and fast response. Numerical design using the finite element method (FEM) was conducted to investigate the steady characteristics (displacement, stiffness, stress, and strain) and dynamic characteristic of resonance frequency. According to calculation results, the major characteristics obtained along XYZ axes are as follows: displacements induced are 10.06, 10.28, and 20.31 μm due to the applied voltage being 50 V; stiffness are 112.84, 110.31, and 223.34 kN/mm; the maximum stresses at the hinges are 9.78, 10.9, and 100.56 N/mm2, which are lower than the allowable stress of aluminum used; and the resonant frequencies are 1.0, 0.64, and 0.4 kHz, respectively. Experimental examinations regarding to the resonant frequencies were performed with a maximum deviation of 16% along the Z-axis compared to the simulation result. As a result of the investigation, it is expected that the 3-axis stage can be effectively applied to implement a FTS.

The vibration of a corrugated carbon fibre pressure vessel under external hydrostatic pressure

2000 ◽  
Vol 214 (10) ◽  
pp. 1299-1311 ◽  
Author(s):  
C T F Ross ◽  
A P F Little
Keyword(s):  
Carbon Fibre ◽  
Water Pressure ◽  
Periodic Excitation ◽  
The Finite Element Method ◽  
External Hydrostatic Pressure ◽  
Surrounding Water ◽  
Resonant Frequencies ◽  
External Water Pressure ◽  
External Water ◽  
Good Agreement

The paper presents a theoretical and an experimental investigation into the vibration of a corrugated carbon fibre cylinder in air and under external water pressure. The theoretical investigation was via the finite element method, where both the shell and the surrounding water were modelled with axisymmetric finite elements. In the case of the shell, the element allowed for orthotropicity and in the case of the water, the element was a solid element with an isoparametric cross-section. Good agreement was found between experiment and theory for both the vibration in air and the vibration under external water pressure. The results showed that as the external water pressure was increased, the resonant frequencies decreased. This appeared to agree with previous findings that a form of dynamic buckling could occur when the vibration eigenmode was the same form as the buckling eigenmode, in response to a periodic excitation force.

scholarly journals BEM and FEM results of displacements in a poroelastic column

2012 ◽  
Vol 22 (4) ◽  
pp. 883-896 ◽  
Author(s):  
Bettina Albers ◽  
Stavros A. Savidis ◽  
H. Ercan Taşan ◽  
Otto von Estorff ◽  
Malte Gehlken
Keyword(s):  
Finite Element Method ◽  
Permeability Coefficient ◽  
Analytic Solution ◽  
The Finite Element Method ◽  
Practical Applications ◽  
Poroelastic Media ◽  
Two Component ◽  
Solution Methods ◽  
The Impact ◽  
Element Method

The dynamical investigation of two-component poroelastic media is important for practical applications. Analytic solution methods are often not available since they are too complicated for the complex governing sets of equations. For this reason, often some existing numerical methods are used. In this work results obtained with the finite element method are opposed to those obtained by Schanz using the boundary element method. Not only the influence of the number of elements and time steps on the simple example of a poroelastic column but also the impact of different values of the permeability coefficient is investigated.

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