scholarly journals Investigation on Resistance, Squat and Ship-Generated Waves of Inland Convoy Passing Bridge Piers in a Confined Waterway

2021 ◽  
Vol 9 (10) ◽  
pp. 1125
Author(s):  
Peng Du ◽  
Abdellatif Ouahsine ◽  
Philippe Sergent ◽  
Yannick Hoarau ◽  
Haibao Hu
Keyword(s):  
Stokes Equations ◽  
Lateral Position ◽  
Wave Pattern ◽  
Body Motion ◽  
Bridge Piers ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Sliding Mesh ◽  
Experimental Approaches ◽  
Mesh Technique

The average and unsteady hydrodynamics of an inland convoy passing bridge piers in a confined waterway were investigated using both numerical and experimental approaches. The numerical simulations are realized by solving the RANS (Reynolds-averaged Navier–Stokes) equations accounting for the solid body motion using the sliding mesh technique, while the experiments were carried out in the towing tank. The advancing resistance, trim, sinkage and ship-generated waves were analyzed as functions of the water depth, distance between bridge piers, draught and velocity. The existence of the piers is found to only influence the transient hydrodynamics of the convoy, but not the averaged properties. The ship-generated waves, especially the wave profiles at a specific lateral position, were characterized. Two wave crests exist at the pier position because of the additional reflections, creating a very complex wave pattern in the confined waterway.

scholarly journals Numerical investigation of a small water turbine used for the power supply of underwater vehicles

2018 ◽  
Vol 10 (6) ◽  
pp. 168781401878365 ◽  
Author(s):  
Zhaoyong Mao ◽  
Jingang Bai
Keyword(s):  
Stokes Equations ◽  
Underwater Vehicles ◽  
Geometric Parameters ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Sliding Mesh ◽  
Small Water ◽  
Water Turbine ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

The development of underwater vehicles is facing the problem of sustainable energy supply. This study introduces a small water turbine, the Lenz turbine, for energy generation from the ocean currents which will provide energy for the underwater vehicles. Computational fluid dynamics simulations of the effect of geometric parameters, including the blade radius, chord length, and pitch angle, on the performance of the turbine are conducted. The Reynolds-Averaged Navier–Stokes equations are numerically solved with a sliding mesh method. Thirteen sets of tests in total are performed at different values of tip-speed ratios. The tests are divided into three groups to study the effect of the three parameters mentioned above, separately. The obtained power coefficients, coefficient of torque, and the dynamic torque on a blade are then compared in each group of tests. Pressure contours and velocity contours are given to explain the reason how the geometric parameters affect the rotor performance.

Viscosity Effects on the Radiation Hydrodynamics of Horizontal Cylinders

1991 ◽  
Vol 113 (4) ◽  
pp. 334-343 ◽  
Author(s):  
R. W. Yeung ◽  
C.-F. Wu
Keyword(s):  
Numerical Solutions ◽  
Stokes Equations ◽  
Small Body ◽  
Low Frequency ◽  
Body Motion ◽  
Navier Stokes ◽  
Inviscid Fluid ◽  
Viscous Effects ◽  
Navier Stokes Equations ◽  
Horizontal Cylinders

The problem of a body oscillating in a viscous fluid with a free surface is examined. The Navier-Stokes equations and boundary conditions are linearized using the assumption of small body-motion to wavelength ratio. Generation and diffusion of vorticity, but not its convection, are accounted for. Rotational and irrotational Green functions for a divergent and a vorticity source are presented, with the effects of viscosity represented by a frequency Reynolds number Rσ = g2/νσ3. Numerical solutions for a pair of coupled integral equations are obtained for flows about a submerged cylinder, circular or square. Viscosity-modified added-mass and damping coefficients are developed as functions of frequency. It is found that as Rσ approaches infinity, inviscid-fluid results can be recovered. However, viscous effects are important in the low-frequency range, particularly when Rσ is smaller than O(104).

scholarly journals Physical and numerical analysis of the front of a gravity current on a horizontal bottom

1998 ◽  
Vol 26 ◽  
pp. 289-295
Author(s):  
Mohamed Naaim ◽  
Thierry Pellarin
Keyword(s):  
Numerical Model ◽  
Stokes Equations ◽  
Gravity Current ◽  
Processing System ◽  
The Body ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Experimental Approaches ◽  
Two Parameters ◽  
Two Stages

In this paper, numerical and experimental approaches are applied to analyse the dynamics of the front of a gravity current. This study focused on two parameters: internal density and velocity fields. The salt concentration was determined by a potentiometric process. The internal velocities were determined using an optical device and an image-processing system. The structure of the head of the gravity current was analysed. Its density was measured and two stages of evolution were observed. This analysis allows us to coufirm the existence of two important stages. Forxf<xs, where the dynamics depend on the initial condition, the flow consists of a head and body and the front density is constant. Forxf>xs, we show that the density of the front decreases and evolves towards the Hallworth and others (1993) law. From a comparison between the experiments and the numerical model, we show that the numerical model, which is based on Navier–Stokes equations and on thek−Lturbulence model (whereLis the height of the gravity current), can predict well flow in the slump regime and in the inertia–buoyancy regime with smoothed results in the transition from the head to the body of the gravity current.

Numerical Simulation of Vortex Induced Vibration Using the K-ε Model

2006 ◽  
Author(s):  
Juan B. V. Wanderley ◽  
Gisele H. B. Souza ◽  
Carlos Levi
Keyword(s):  
Numerical Simulation ◽  
Stokes Equations ◽  
Body Motion ◽  
Navier Stokes ◽  
Experimental Investigations ◽  
Real Problem ◽  
Navier Stokes Equations ◽  
Vortex Induced Vibration ◽  
Selection Of

Numerical simulations of Vortex Induced Vibration have been failing to duplicate accurately experimental data mostly due to the complexity of the physics involved in the real problem. Therefore, a careful and comprehensive investigation on CFD algorithms is still required to indicate the most suitable numerical scheme to handle such a complicate problem. Grid generation, boundary condition implementation, and coupling between the fluid flow governing equations and body motion equation are known to have strong influence on the qualities of the numerical results. This work presents results obtained from a long-term investigation featuring different CFD methods. The investigations enabled the selection of a very effective algorithm that showed an outstanding agreement between experiment and numerical simulation of the VIV phenomenon. Good agreement is obtained in the entire range of reduced velocity covered by the experimental investigations. The successful algorithm discussed here applies the Beam and Warming implicit scheme to solve the two-dimensional slightly compressible Navier–Stokes equations with the K-ε turbulence model to simulate the turbulent flow at the wake of the cylinder.

scholarly journals Numerical simulation of supersquare patterns in Faraday waves

2015 ◽  
Vol 772 ◽  
Author(s):  
L. Kahouadji ◽  
N. Périnet ◽  
L. S. Tuckerman ◽  
S. Shin ◽  
J. Chergui ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Outer Wall ◽  
Wave Pattern ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Critical Wavelength ◽  
Characteristic Wavelength ◽  
Cylindrical Domains ◽  
Lagrangian Tracking

We report the first simulations of the Faraday instability using the full three-dimensional Navier–Stokes equations in domains much larger than the characteristic wavelength of the pattern. We use a massively parallel code based on a hybrid front-tracking/level-set algorithm for Lagrangian tracking of arbitrarily deformable phase interfaces. Simulations performed in square and cylindrical domains yield complex patterns. In particular, a superlattice-like pattern similar to those of Douady & Fauve (Europhys. Lett., vol. 6, 1988, pp. 221–226) and Douady (J. Fluid Mech., vol. 221, 1990, pp. 383–409) is observed. The pattern consists of the superposition of two square superlattices. We conjecture that such patterns are widespread if the square container is large compared with the critical wavelength. In the cylinder, pentagonal cells near the outer wall allow a square-wave pattern to be accommodated in the centre.

scholarly journals NUMERICAL SIMULATIONS OF LOW REYNOLDS NUMBER FLOWS PAST ELASTICALLY MOUNTED CYLINDER

2012 ◽  
Vol 11 (1-2) ◽  
pp. 61
Author(s):  
R. A. Gonçalves ◽  
P. R. F. Teixeira ◽  
E. Didier
Keyword(s):  
Vortex Shedding ◽  
Stokes Equations ◽  
Reynolds Numbers ◽  
Body Motion ◽  
Petroleum Exploration ◽  
Navier Stokes ◽  
Generation Process ◽  
Navier Stokes Equations ◽  
Eulerian Formulation ◽  
Low Reynolds

The vortex-induced vibration (VIV) phenomenon has drawn the attention of researchers in Engineering for several decades. An example is the riser used for petroleum exploration, in which it is subjected to marine flows that may cause oscillations due to vortex shedding. In this paper, numerical analyses of the phenomena that occur in the interaction among flows at low Reynolds numbers and elastically mounted cylinders are presented. The simulation is carried out by using the numerical model Ifeinco that uses a semi-implicit two-step Taylor-Galerkin method to discretize the Navier-Stokes equations and the arbitrary Lagrangean-Eulerian formulation to follow the cylinder motion. The rigid body motion description is calculated by using the Newmark method. Firstly, the characteristics of the vortex generation process for the fixed cylinder are analyzed. In this case, the Strouhal number, the mean drag and the RMS lift coefficients for Reynolds numbers ranging from 90 to 140 are shown. Afterwards, an analysis of a flexible supported cylinder (with a spring and a damper) in transverse direction subject to flows with Reynolds numbers ranging from 90 to 140 is carried out. The cylinder displacement and the vibration frequencies are studied; the synchronization between the vortex shedding and the vibration frequency (lock-in) is analyzed. Similar results to the experimental ones developed by Anagnostopoulos and Bearman (1992) were obtained in this study.

scholarly journals Physical and numerical analysis of the front of a gravity current on a horizontal bottom

1998 ◽  
Vol 26 ◽  
pp. 289-295
Author(s):  
Mohamed Naaim ◽  
Thierry Pellarin
Keyword(s):  
Numerical Model ◽  
Stokes Equations ◽  
Gravity Current ◽  
Processing System ◽  
The Body ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Experimental Approaches ◽  
Two Parameters ◽  
Two Stages

In this paper, numerical and experimental approaches are applied to analyse the dynamics of the front of a gravity current. This study focused on two parameters: internal density and velocity fields. The salt concentration was determined by a potentiometric process. The internal velocities were determined using an optical device and an image-processing system. The structure of the head of the gravity current was analysed. Its density was measured and two stages of evolution were observed. This analysis allows us to coufirm the existence of two important stages. For xf < xs, where the dynamics depend on the initial condition, the flow consists of a head and body and the front density is constant. For xf > xs, we show that the density of the front decreases and evolves towards the Hallworth and others (1993) law. From a comparison between the experiments and the numerical model, we show that the numerical model, which is based on Navier–Stokes equations and on the k−L turbulence model (where L is the height of the gravity current), can predict well flow in the slump regime and in the inertia–buoyancy regime with smoothed results in the transition from the head to the body of the gravity current.

Numerical Modeling of Unsteady Flow Through a Turbomachine Stage

1998 ◽  
Author(s):  
R. I. Issa ◽  
M. A. Sadri
Keyword(s):  
Numerical Method ◽  
Periodic Boundary ◽  
Stokes Equations ◽  
Unsteady Flows ◽  
Periodic Boundary Conditions ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Sliding Mesh ◽  
Flow Through ◽  
Implicit Numerical Method

A numerical method is presented for the simulation of unsteady flows through turbomachine stages with unequal numbers of rotor and stator blades. The method solves the two-dimensional incompressible, unsteady, ensemble averaged, Navier-Stokes equations together with transport equations for the k–ϵ turbulence model employed to simulate the effects of turbulence. The method employs an implicit pressure-based finite volume discretisation procedure. In order to simulate the flow in the rotor and stator passages simultaneously, a sliding mesh methodology is developed which allows the mesh mapping the rotor domain to move in a sliding action relative to the static mesh which maps the stator passage. Phase-lagged periodic boundary conditions are implemented in the context of the implicit numerical method developed to handle unequal rotor and stator pitches efficiently. The effectiveness and accuracy of the method are assessed against data for a rotor/stator configuration with unequal pitches in adjacent rows of a low speed turbine.

Turbulence Models Performance Assessment for Pressure Prediction during Cylinder Water Entry

2012 ◽  
Vol 224 ◽  
pp. 225-229 ◽  
Author(s):  
Bao Dong Guo ◽  
Pei Qing Liu ◽  
Qiu Lin Qu ◽  
Yue Li Cui
Keyword(s):  
Stokes Equations ◽  
Turbulence Models ◽  
Water Entry ◽  
Navier Stokes ◽  
Engineering Practice ◽  
Two Dimensional ◽  
Navier Stokes Equations ◽  
Dynamic Mesh Technique ◽  
Volume Method ◽  
Mesh Technique

Numerical simulations of two-dimensional cylinder free droping into water are presented based on volume of fluid (VOF) method and dynamic mesh technique. Solutions with a time-accurate finite-volume method (FVM) were generated based on the unsteady compressible ensemble averaged Navier-Stokes equations for the air and the unsteady incompressible ensemble averaged Navier-Stokes equations for the water. Computed pressure histories of the cylinder were compared with experimentally measured values. The performance of various turbulence models for pressure prediction was assessed. The results indicate that Realizable k-epsilon model with Enhanced Wall Treatment is the best choice for engineering practice.

Global stability of combination of viscous contact wave with rarefaction wave for compressible Navier–Stokes equations with temperature-dependent viscosity

2017 ◽  
Vol 27 (12) ◽  
pp. 2321-2379 ◽  
Author(s):  
Bingkang Huang ◽  
Yongkai Liao
Keyword(s):  
Rarefaction Wave ◽  
Stokes Equations ◽  
Initial Perturbation ◽  
Main Idea ◽  
Wave Pattern ◽  
Navier Stokes ◽  
Heat Conducting ◽  
Temperature Dependent Viscosity ◽  
Navier Stokes Equations ◽  
Contact Wave

We study the nonlinear stability of a composite wave pattern, which is a combination of a viscous contact wave with a rarefaction wave, to the Cauchy problem of one-dimensional compressible Navier–Stokes equations for a viscous and heat conducting ideal polytropic gas with large initial perturbation when the transport coefficients depend on both temperature and density. Our main idea is to use the “smallness mechanism” induced by the structures of the equations under consideration and the smallness of the strengths of the two elementary waves to control the possible growth of the solutions caused by the nonlinearities of the equations, the interactions between the solutions themselves and the wave pattern, and the interactions of waves between different families. The main ingredient in the analysis is to derive the uniform positive lower and upper bounds on the specific volume and the temperature.

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