A Numerical Study on Sloshing Flows Coupled with Ship Motion—The Anti-Rolling Tank Problem

2002 ◽  
Vol 46 (01) ◽  
pp. 52-62
Author(s):  
Yonghwan Kim
Keyword(s):  
Experimental Data ◽  
Numerical Method ◽  
Numerical Study ◽  
Computational Study ◽  
Three Dimensional ◽  
Ship Motion ◽  
Coupling Effects ◽  
Time Step ◽  
Numerical Result ◽  
Hull Forms

A computational study on the sloshing problem coupled with ship motion in waves is introduced. The ship motion excites the sloshing flow in the ship's liquid cargo, and the slosh-induced forces and moments affect the ship motion in return. This study applies a numerical method to solve the coupling problem of the ship motion and sloshing flow. In particular, it concentrates on the anti-rolling tank, which has the most significant coupling effects of two problems. The three-dimensional sloshing flow has been simulated using the finite-difference method, while the ship motion has been obtained using a time-domain panel method. At each time step, the instantaneous displacement, velocity and acceleration of ship motion have been applied to the excitation of liquid motion, and the corresponding slosh-induced forces and moments have been added to the wave-induced excitation. The computational model is a modified S175 hull, and the computational results have been compared with the experimental data of a supply vessel. Although the two hull forms are not identical, the numerical result for the modified S175 hull shows the same trend of the roll RAOs with experimental data when the anti-rolling tanks are considered. Therefore, the numerical method introduced in this study is expected to be very useful in observing the coupling effects of sloshing and ship motion problems.

Viscous Flow Computations on a Smooth Cylinders: A Detailed Numerical Study With Validation

2007 ◽  
Author(s):  
Guilherme Vaz ◽  
Christophe Mabilat ◽  
Remmelt van der Wal ◽  
Paul Gallagher
Keyword(s):  
Experimental Data ◽  
Viscous Flow ◽  
Numerical Study ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Time Step ◽  
Drag Forces

The objective of this paper is to investigate several numerical and modelling features that the CFD community is currently using to compute the flow around a fixed smooth circular cylinder. Two high Reynolds numbers, 9 × 104 and 5 × 105, are chosen which are in the so called drag-crisis region. Using a viscous flow solver, these features are assessed in terms of quality by comparing the numerical results with experimental data. The study involves grid sensitivity, time step sensitivity, the use of different turbulence models, three-dimensional effects, and a RANS/DES (Reynolds Averaged Navier Stokes, Detached Eddy Simulation) comparison. The resulting drag forces and Strouhal numbers are compared with experimental data of different sources. Major flow features such as velocity and vorticity fields are presented. One of the main conclusions of the present study is that all models predict forces which are far from the experimental values, particularly for the higher Reynolds numbers in the drag-crisis region. Three-dimensional and unsteadiness effects are present, but are only fully captured by sophisticated turbulence models or by DES. DES seems to be the key to better solve the flow problem and obtain better agreement with experimental data. However, its considerable computational demands still do not allow to use it for engineering design purposes.

Numerical Study on Ship Motion Fully Coupled with LNG Tank Sloshing in CFD Method

2019 ◽  
Vol 16 (06) ◽  
pp. 1840022 ◽  
Author(s):  
Yuan Zhuang ◽  
Decheng Wan
Keyword(s):  
Incident Wave ◽  
Numerical Study ◽  
Three Dimensional ◽  
Ship Motion ◽  
Wave Flow ◽  
Motion Responses ◽  
Lng Tank ◽  
Cfd Method ◽  
Tank Sloshing ◽  
Fully Coupled

In this paper, numerical simulations of ship motion coupled with LNG tank sloshing in waves are considered. The fully coupled problems are performed by our in-house RANS/DES solver, naoe-FOAM-SJTU. The internal tank sloshing and external wave flow are solved simultaneously. The considered model is a three-dimensional simplified LNG FPSO with two prismatic tanks. The ship motion responses are carried out in beam waves to compare with existing experimental data to validate this solver. The coupling effects between ship motion and sloshing tanks are observed. The anti-rolling characteristics are found, and this kind of characteristic is obvious in low-filling conditions. Different incident wave amplitudes and frequencies are considered. When the incident wave frequency is close to ship motion natural frequency, the ship motion response is strong and an overturning behavior in sloshing tanks is observed. Meanwhile, impact pressures on bulkhead are also discussed. The pressure signal explains the phenomenon in tanks we discussed before.

Numerical Study on the Effect of Twin-Tube Shield Excavation on Adjacent Pipelines

2012 ◽  
Vol 170-173 ◽  
pp. 1491-1496 ◽  
Author(s):  
Xin Wang ◽  
De Shen Zhao ◽  
Meng Lin Xu
Keyword(s):  
Distribution Curve ◽  
Numerical Study ◽  
Three Dimensional ◽  
Element Model ◽  
Stress Release ◽  
Tunnel Excavation ◽  
Normal Distribution Curve ◽  
Numerical Result ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Based on Dalian subway line 2 from Chun-guang street station to Xiang-gong street station,the three dimensional finite element model was established using FLAC3D software , the shield excavated surface against the pressure, the stress release, the shield tail escape and grouting. The numerical result indicated that the pipeline displacement increases gradually with the advance of the tunnel excavation. When one-sided tunnel excavation is carried out, the largest displacement is located at the tunnel axis, the settling curve basically conforms to the normal distribution curve with the unimodal characteristic. The excavation of right-side tunnel is disadvantageous to the left-side tunnel. The analysis indicated that the pipeline is in a secure state. The work in this paper provided theoretical basis and the practical guidance to this project.

Experimental and Computational Study of Oscillating Turbine Cascade and Influence of Part-Span Shrouds

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
X. Q. Huang ◽  
L. He ◽  
David L. Bell
Keyword(s):  
Experimental Data ◽  
Computational Study ◽  
Three Dimensional ◽  
Unsteady Flows ◽  
Correction Method ◽  
Influence Coefficient ◽  
Turbine Cascade ◽  
Test Configuration ◽  
Practical Applications ◽  
Influence Coefficient Method

This paper presents a combined experimental and computational study of unsteady flows in a linear turbine cascade oscillating in a three-dimensional bending/flapping mode. Detailed experimental data are obtained on a seven-bladed turbine cascade rig. The middle blade is driven to oscillate and oscillating cascade data are obtained using an influence coefficient method. The numerical simulations are performed by using a 3D nonlinear time-marching Navier–Stokes flow solver. Single-passage domain computations for arbitrary interblade phase angles are achieved by using the Fourier shape correction method. Both measurements and predictions demonstrate a fully 3D behavior of the unsteady flows. The influence of the aerodynamic blockage introduced by part-span shrouds on turbine flutter has been investigated by introducing flat plate shaped shrouds at 75% span. In contrast to practical applications, in the present test configuration, the mode of vibration of the blades remains unchanged by the introduction of the part-span shroud. This allows the influence of the aerodynamic blockage introduced by the part-span shroud to be assessed in isolation from the change in mode shape. A simple shroud model has been developed in the computational solver. The computed unsteady pressures around the shrouds are in good agreement with the experimental data, demonstrating the validity of the simple shroud model. Despite of notable variations in local unsteady pressures around the shrouds, the present results show that the blade aerodynamic damping is largely unaffected by the aerodynamic blockage introduced by part-span shrouds.

Applicability of Net-Section Collapse Load Approach to Maximum Load Predictions of Multiple Circumferential Cracked Pipes: Numerical Study

2015 ◽  
Author(s):  
Myeong-Woo Lee ◽  
Seung-Jae Kim ◽  
So-Dam Lee ◽  
Jun-Young Jeon ◽  
Yun-Jae Kim
Keyword(s):  
Experimental Data ◽  
Numerical Method ◽  
Test Data ◽  
Numerical Study ◽  
Maximum Load ◽  
Load Carrying Capacity ◽  
Collapse Load ◽  
Crack Geometry ◽  
Large Sets ◽  
Load Carrying

To estimate maximum load-carrying capacity of pipes with multiple circumferential cracks, the net-section collapse load approach has been proposed. Although the proposed method has been validated against pipe test data, experimental data are quite limited due to large sets of variables to be considered. In this paper, a numerical method is proposed to generate virtual pipe test data with wide ranges of crack geometry and interspacing. To get confidence of the proposed numerical method, it is firstly applied to simulate existing 4-inch diameter schedule 80 pipes with two circumferential cracks. Predicted maximum loads agree well with experimental data. Then the proposed method is applied to generate maximum loads for wider ranges of crack geometry and loading conditions. It is found that the net-section collapse load approach works well for all cases considered.

A Navier–Stokes Analysis of Airfoils in Oscillating Transonic Cascades for the Prediction of Aerodynamic Damping

1997 ◽  
Vol 119 (1) ◽  
pp. 77-84 ◽  
Author(s):  
R. S. Abhari ◽  
M. Giles
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Outer Region ◽  
Navier Stokes ◽  
Compressor Cascade ◽  
Time Step ◽  
Aerodynamic Damping ◽  
Transonic Compressor ◽  
Standard Configuration ◽  
The Impact

An unsteady, compressible, two-dimensional, thin shear layer Navier–Stokes solver is modified to predict the motion-dependent unsteady flow around oscillating airfoils in a cascade. A quasi-three-dimensional formulations is used to account for the stream-wise variation of streamtube height. The code uses Ni’s Lax–Wendroff algorithm in the outer region, an implicit ADI method in the inner region, conservative coupling at the interface, and the Baldwin–Lomax turbulence model. The computational mesh consists of an O-grid around each blade plus an unstructured outer grid of quadrilateral or triangular cells. The unstructured computational grid was adapted to the flow to better resolve shocks and wakes. Motion of each airfoil was simulated at each time step by stretching and compressing the mesh within the O-grid. This imposed motion consists of harmonic solid body translation in two directions and rotation, combined with the correct interblade phase angles. The validity of the code is illustrated by comparing its predictions to a number of test cases, including an axially oscillating flat plate in laminar flow, the Aeroelasticity of Turbomachines Symposium Fourth Standard Configuration (a transonic turbine cascade), and the Seventh Standard Configuration (a transonic compressor cascade). The overall comparison between the predictions and the test data is reasonably good. A numerical study on a generic transonic compressor rotor was performed in which the impact of varying the amplitude of the airfoil oscillation on the normalized predicted magnitude and phase of the unsteady pressure around the airfoil was studied. It was observed that for this transonic compressor, the nondimensional aerodynamic damping was influenced by the amplitude of the oscillation.

scholarly journals Numerical Simulation of the Dispersion and Deposition of a Spray Carried by a Pulsating Airflow in a Patient-Specific Human Nasal Cavity

2017 ◽  
Author(s):  
Ali Farnoud ◽  
Xinguang Cui ◽  
Ingo Baumann ◽  
Eva Gutheil
Keyword(s):  
Nasal Cavity ◽  
High Performance ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Patient Specific ◽  
Process Time ◽  
Nasal Valve ◽  
Time Step ◽  
Real Process

The present numerical study concerns the dispersion and deposition of a nasal spray in a patient-specific human nose. The realistic three-dimensional geometry of the nasal cavity is reconstructed from computer tomography (CT) scans. Identification of the region of interest, removal of artifacts, segmentation, generation of the .STL file and the triangulated surface grid are performed using the software packages ImageJ, meshLab, and NeuRA2. An unstructured computational volume grid with approximately 15 million tetrahedral grid cells is generated using the software Ansys ICEM-CFD 11.0. An unsteady Eulerian-Lagrangian formulation is used to describe the airflow and the spray dispersion and deposition in the realistic human nasal airway using two-way coupling. A new solver called pimpleParcelFoam is developed, which combines the lagrangianParcel libraries with the pimpleFoam solver within the software package OpenFOAM 3.0.0. A large eddy simulation (LES) with the dynamic sub-grid scale (SGS) model is performed to study the spray in both a steady and a pulsating airflow with an inflow rate of 7.5 L/min (or maximum value in case of the pulsating spray) and a frequency of 45 Hz for pulsation as used in commercial inhalation devices. 10,000 mono-disperse particles with the diameters of 2.4 µm and 10 µm are uniformly injected at the nostrils. In order to fulfil the stability conditions for the numerical solution, a constant time-step of 10−5 s is implemented. The simulations are performed for a real process time of 1 s, since after the first second of the process, all particles have escaped through the pharynx or they are deposited at the surface of the nasal cavity. The numerical computations are performed on the high-performance computer bwForCluster MLS&WISO Production using 256 processors, which take around 32 and 75 hours for steady and pulsating flow simulation, respectively. The study shows that the airflow velocity reaches its maximum values in the nasal valve, in parts of the septum and in the nasopharynx. A complex airflow is observed in the vestibule and in the nasopharynx region, which may directly affect the dispersion and deposition pattern of the spray. The results reveal that the spray tends to deposit in the nasal valve, the septum and in the nasopharynx due to the change in the direction of the airflow in these regions. Moreover, it is found that due to the pulsating airflow, the aerosols are more dispersed and penetrate deeper into the posterior regions and the meatuses where the connections to the sinuses reside.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4628

A Non-Linear Numerical Method for the Simulation of Parametric Roll Resonance in Regular Waves

2008 ◽  
Author(s):  
T. M. Ahmed ◽  
E. J. Ballard ◽  
D. A. Hudson ◽  
P. Temarel
Keyword(s):  
Numerical Method ◽  
Potential Flow ◽  
Degrees Of Freedom ◽  
Linear Time ◽  
Three Dimensional ◽  
Regular Waves ◽  
Time Step ◽  
Parametric Roll ◽  
Non Linear ◽  
Parametric Roll Resonance

In this paper, a non-linear time-domain method is used for the prediction of parametric roll resonance in regular waves, assuming the ship to be a system with three degrees of freedom in heave, pitch and roll. Coupled heave and pitch motions are obtained using a three-dimensional frequency-domain potential flow method which also provides the requisite hydrodynamic data of the ship in roll i.e. the potential flow based added inertia and damping. Periodic changes in the underwater hull geometry due to heave, pitch and the wave profile are calculated as a function of the instantaneous breadth. This is carried out using a two-dimensional approach i.e. for sections along the ship and at each time step. This formulation leads to a mathematical model that represents the roll equation of motion with third order non-linearities in the parametric excitation terms. Non-linearities in the roll damping and restoring terms are also accounted for. This method has been applied to two different hull forms, a post-Panamax C11 class containership and a transom stern Trawler, both travelling in regular waves. Special attention is focused on the influence of different operational aspects on parametric roll. Obtained results demonstrate that this numerical method succeeds in producing results similar to those available in the literature, both numerical and experimental.

Numerical study of flow pattern around lateral intake in a curved channel

2019 ◽  
Vol 30 (11) ◽  
pp. 1950083 ◽  
Author(s):  
Hossien Montaseri ◽  
Hossein Asiaei ◽  
Abdolhossein Baghlani ◽  
Pourya Omidvar
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Flow Pattern ◽  
Numerical Study ◽  
Numerical Models ◽  
Three Dimensional ◽  
Curved Channel ◽  
Channel Bend ◽  
Outer Bank ◽  
Center Region

This paper deals with numerical study of flow field in a channel bend in presence of a lateral intake using three-dimensional numerical model SSIIM2. The effects of bend on the structure of the flow around the intake are investigated and compared with the experimental data. The tests are carried out in a U-shaped channel bend with a lateral intake. The intake is located at the outer bank of an 180∘ bend at position 115∘ with 45∘ diversion angle and the experimental data can be used to calibrate and validate numerical models. The results show that both the center-region and outer-bank cross-stream circulations are observed in the experiments while only the former is captured by the numerical model due to the limitations of the turbulence model. In the curved channel after the intake, both experimental and numerical results show another type of bi-cellular circulations in which clockwise center-region circulations and counterclockwise circulations near the inner bank and the free surface (inner-bank circulations) are captured. The study shows that the numerical model very satisfactorily predicts streamlines, velocity field and flow pattern in the channel and in vicinity of the intake. Investigation of flow pattern around lateral intake in channel bends shows that contrary to the case of flow diversion in straight channels, the width of the dividing stream surface near water surface level is greater than that of near bed level. Finally, the effects of position and diversion angle of the lateral intake, discharge ratio and upstream Froude number on the flow pattern are investigated.

A Computational Study of Gas-solid Flow in an Enhanced Solid Entrainment (ESE) Nozzle System

2005 ◽  
Vol 3 (1) ◽  
Author(s):  
Maopei Cui ◽  
Anthony G Straatman ◽  
Chao Zhang
Keyword(s):  
Draft Tube ◽  
Numerical Study ◽  
Computational Study ◽  
Full Range ◽  
Three Dimensional ◽  
Separation Distance ◽  
Solid Particles ◽  
Eulerian Model ◽  
Flow Parameters ◽  
Multi Phase

A numerical study has been undertaken to explore the influence of geometry and flow parameters on the entrainment of solid in an ESE nozzle system immersed in a fluidized riser. A fully three-dimensional computational model of the nozzle system has been developed and all appropriate approximations and simplifications are described. A multi-phase Eulerian-Eulerian model incorporating the kinetic theory for solid particles is used. Numerical results are obtained using the commercial Computational Fluid Dynamics software FLUENT. The results indicate that solid entrainment in the ESE system is a strong function of both geometry and flow. The optimal entrainment is seen to occur when the ratio of the draft tube diameter D to separation distance I is approximately unity. At this value, the jet of injected gas is seen to spread fully into the opening of the draft tube causing the highest transport of solid particles through the tube. The entrainment is shown to increase with increasing jet velocity across the full range of flows considered. The results are consistent with similar experimental results. The results of this study should find immediate application in the design and implementation of ESE nozzle systems.

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