scholarly journals On the behavior of nonlinear hydrodynamic coefficients of a submerged cylinder beneath the water surface

2021 ◽  
Author(s):  
Nguyen Van My ◽  
Le Anh Tien ◽  
Phan Hoang Nam ◽  
Nguyen Quoc Khanh ◽  
Chau Van Than ◽  
...  
Keyword(s):  
Free Surface ◽  
State Diagram ◽  
Free Surface Flow ◽  
Flow Fields ◽  
Horizontal Cylinder ◽  
Surface Flow ◽  
Navier Stokes ◽  
Cylinder Surface ◽  
Hydrodynamic Coefficients ◽  
Submerged Cylinder

This study aims at numerically exploring the behavior of flow fields and nonlinear hydrodynamic coefficients of a horizontal cylinder beneath the free surface flow considering the effects of nonlinear surface waves and various cylinder shapes. The computational model is based on two-dimensional incompressible Navier-Stokes solvers along with the treatment of the free surface flow using the volume of fluid method. The effect of the turbulent flow is also considered by using the shear stress transport turbulence model. The simulation result of a benchmark case study of the submerged cylinder is first validated with available experiment data, where a mesh convergence analysis is also performed. Afterward, the flow fields and hydrodynamic force coefficients around the cylinder surface are analyzed, and the influences of various cylinder shapes and Reynolds numbers on the hydrodynamic coefficients are investigated. A state diagram representing the hydrodynamic behavior including stable and unstable stages is finally proposed; this is an important criterion for the practice design of submerged civil structures under the free surface flow.

Surface Ship Total Resistance Prediction Based on a Nonlinear Free Surface Potential Flow Solver and a Reynolds-Averaged Navier-Stokes Viscous Correction

2007 ◽  
Vol 51 (01) ◽  
pp. 47-64
Author(s):  
James C. Huan ◽  
Thomas T. Huang
Keyword(s):  
Free Surface ◽  
Surface Potential ◽  
Potential Flow ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Navier Stokes ◽  
Total Resistance ◽  
Flow Solver ◽  
Resistance Prediction ◽  
Nonlinear Free Surface

A fast turnaround and an accurate computational fluid dynamics (CFD) approach for ship total resistance prediction is developed. The approach consists of a nonlinear free surface potential flow solver (PShip code) with a wet-or-dry transom stern model, and a Reynolds-averaged Navier-Stokes (RANS) equation solver that solves viscous free surface flow with a prescribed free surface given from the PShip. The prescribed free surface RANS predicts a viscous correction to the pressure resistance (viscous form) and viscous flow field around the hull. The viscous free surface flow solved this way avoids the time-consuming RANS iterations to resolve the free surface profile. The method, however, requires employing a flow characteristic-based nonreflecting boundary condition at the free surface. The approach can predict the components of ship resistance, the associated wave profile around the hull, and the sinkage and trim of the ship. Validation of the approach is presented with Wigley, Series 60 (CB = 0.6), and NSWCCD Model 5415 hulls. An overall accuracy of ±2% for ship total resistance prediction is achieved. The approach is applied to evaluating the effects of a stern flap on a DD 968 model on ship performance. An empirical viscous form resistance formula is also devised for a quick ship total resistance estimate.

Unstructured Grid Based Reynolds-Averaged Navier-Stokes Method for Liquid Tank Sloshing

2005 ◽  
Vol 127 (3) ◽  
pp. 572-582 ◽  
Author(s):  
Shin Hyung Rhee
Keyword(s):  
Free Surface ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Navier Stokes ◽  
Governing Equations ◽  
Reconstruction Scheme ◽  
Geometric Reconstruction ◽  
Membrane Type ◽  
Tank Sloshing ◽  
Good Agreement

The present study is concerned with liquid tank sloshing at low filling level conditions. The volume of fluid method implemented in a Navier–Stokes computational fluid dynamics code is employed to handle the free-surface flow of liquid sloshing. The geometric reconstruction scheme for the interface representation is employed to ensure sharpness at the free surface. The governing equations are discretized by second order accurate schemes on unstructured grids. Several different computational approaches are verified and numerical uncertainties are assessed. The computational results are validated against existing experimental data, showing good agreement. The capability is demonstrated for a generic membrane-type liquefied natural gas carrier tank with a simplified pump tower inside. The validation results suggest that the present computational approach is both easy to apply and accurate enough for more realistic problems.

scholarly journals NUMERICAL AND EXPERIMENTAL STUDY OF DAM-BREAK FLOOD PROPAGATION AND ITS IMPLICATION TO SEDIMENT EROSION

2012 ◽  
Vol 1 (33) ◽  
pp. 7
Author(s):  
Hung-Chu Hsu ◽  
A. Torres-Freyermuth ◽  
Tian-Jian Hsu ◽  
Hwung-Hweng Hwung
Keyword(s):  
Free Surface ◽  
Sediment Transport ◽  
Numerical Model ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Transport Processes ◽  
Dam Break ◽  
Navier Stokes ◽  
Suspended Sediment Transport ◽  
Initial Stage

Regarding the hydrodynamics, within the past two decades it has become popular in numerical modeling of free-surface flow to adopt a Reynolds-averaged Navier-Stokes approach, where the volume of fluid (VOF) method is utilized to track the evolution of free-surface. However, this robust numerical model has not been widely applied to the study of sediment transport processes. In this study, we shall extend the numerical model to simulate suspended sediment transport and study the erosion pattern during the initial stage of the dam break flow. We also conducted a series of experiments in a horizontal channel of rectangular section and recorded the snap shots of surface profiles of a dam- break wave during the initial stage of dam-break. Measured data is utilized here to study the hydrodynamics and to validate the numerical model.

scholarly journals Simulation of free-surface flow in a tank using the Navier-Stokes model and unstructured finite volume method

2005 ◽  
Vol 219 (3) ◽  
pp. 251-266 ◽  
Author(s):  
X Zhang ◽  
N M Sudharsan ◽  
R Ajaykumar ◽  
K Kumar
Keyword(s):  
Free Surface ◽  
Finite Volume Method ◽  
Finite Volume ◽  
Free Surface Flow ◽  
Offshore Structures ◽  
Surface Flow ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Volume Method ◽  
Unstructured Finite Volume Method

Modelling free-surface flow has very important applications in many engineering areas such as oil transportation and offshore structures. Current research focuses on the modelling of free surface flow in a tank by solving the Navier-Stokes equation. An unstructured finite volume method is used to discretize the governing equations. The free surface is tracked by dynamically adapting the mesh and making it always surface conforming. A mesh-smoothing scheme based on the spring analogy is also implemented to ensure mesh quality throughout the computaiton. Studies are performed on the sloshing response of a liquid in an elastic container subjected to various excitation frequencies. Further investigations are also carried out on the critical frequency that leads to large deformation of the tank walls. Another numerical simulation involves the free-surface flow past as submerged obstacle placed in the tank to show the flow separation and vortices. All these cases demonstrate the capability of this numerical method in modelling complicated practical problems.

Free Surface Flow Past Ships in Shallow Water

2002 ◽  
Author(s):  
A. Ganguly ◽  
V. Shigunov ◽  
O. Turan
Keyword(s):  
Free Surface ◽  
Stokes Equations ◽  
Near Field ◽  
Free Surface Flow ◽  
Steady State Solution ◽  
Surface Flow ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Medium Speed ◽  
Measured Resistance

A finite volume method with a multiphase type free surface description is employed to calculate the flow around ships in shallow and restricted channels. The flows at critical and supercritical depth Froude numbers (Fnd = 1.0 and Fnd = 1.18) are calculated for Series–60 monohull and a medium speed catamaran. A steady state solution for Reynolds-averaged Navier-Stokes equations with a k-ε turbulence model is obtained by time marching. Computed wave profiles are in good agreement with model tests in the near field of the ship. The computed and measured resistance agree fairly well.

Free-surface flow past a submerged cylinder

2010 ◽  
Vol 22 (S1) ◽  
pp. 209-214 ◽  
Author(s):  
Meng-yu Lin ◽  
Liang-hsiung Huang
Keyword(s):  
Free Surface ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Flow Past ◽  
Submerged Cylinder

Free-Surface Flow and Fluid-Object Interaction Modeling With Emphasis on Ship Hydrodynamics

2011 ◽  
Vol 79 (1) ◽  
Author(s):  
I. Akkerman ◽  
Y. Bazilevs ◽  
D. J. Benson ◽  
M. W. Farthing ◽  
C. E. Kees
Keyword(s):  
Free Surface ◽  
Rigid Body ◽  
Level Set ◽  
Equations Of Motion ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Navier Stokes ◽  
Arbitrary Lagrangian Eulerian ◽  
Ship Hydrodynamics ◽  
Interaction Modeling

This paper presents our approach for the computation of free-surface/rigid-body interaction phenomena with emphasis on ship hydrodynamics. We adopt the level set approach to capture the free-surface. The rigid body is described using six-degree-of-freedom equations of motion. An interface-tracking method is used to handle the interface between the moving rigid body and the fluid domain. An Arbitrary Lagrangian–Eulerian version of the residual-based variational multiscale formulation for the Navier–Stokes and level set equations is employed in order to accommodate the fluid domain motion. The free-surface/rigid body problem is formulated and solved in a fully coupled fashion. The numerical results illustrate the accuracy and robustness of the proposed approach.

Simulation of a Free Surface Flow over a Vertical Weir

2012 ◽  
Vol 256-259 ◽  
pp. 2616-2620
Author(s):  
Y. L. Liu ◽  
Y. Bai
Keyword(s):  
Numerical Simulation ◽  
Free Surface ◽  
Theoretical Analysis ◽  
Flow Field ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Navier Stokes ◽  
Numerical Software ◽  
Typical Time ◽  
Time Point

In this paper the numerical simulation of a free surface flow over a vertical weir with in turns of a scour pool and a small hump weir is presented. Since in this case few of calculative examples adds scour pool and small hump weir in the model, it is meaningful to compute this example using a numerical software which is named Fluent 6.3. The numerical method used consists of Navier–Stokes turbulence solver and k-ε model together with a VOF method and PISO algorithm in pave meshes. Thus, the sketches of flow fields on each typical time point and velocity distributions on each section on 16s are provided to describe flow field accurately. A very good quantitative consequence which accords with hydraulics theoretical analysis has been obtained.

scholarly journals Determinants of modelling choices for 1-D free-surface flow and morphodynamics in hydrology and hydraulics: a review

2016 ◽  
Vol 20 (9) ◽  
pp. 3799-3830 ◽  
Author(s):  
Bruno Cheviron ◽  
Roger Moussa
Keyword(s):  
Free Surface ◽  
Flow Characteristics ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Navier Stokes ◽  
Dimensionless Time ◽  
Dimensionless Numbers ◽  
Model Refinement ◽  
Modelling Strategies ◽  
Spatiotemporal Scales

Abstract. This review paper investigates the determinants of modelling choices, for numerous applications of 1-D free-surface flow and morphodynamic equations in hydrology and hydraulics, across multiple spatiotemporal scales. We aim to characterize each case study by its signature composed of model refinement (Navier–Stokes: NS; Reynolds-averaged Navier–Stokes: RANS; Saint-Venant: SV; or approximations to Saint-Venant: ASV), spatiotemporal scales and subscales (domain length: L from 1 cm to 1000 km; temporal scale: T from 1 s to 1 year; flow depth: H from 1 mm to 10 m; spatial step for modelling: δL; temporal step: δT), flow typology (Overland: O; High gradient: Hg; Bedforms: B; Fluvial: F), and dimensionless numbers (dimensionless time period T*, Reynolds number Re, Froude number Fr, slope S, inundation ratio Λz, Shields number θ). The determinants of modelling choices are therefore sought in the interplay between flow characteristics and cross-scale and scale-independent views. The influence of spatiotemporal scales on modelling choices is first quantified through the expected correlation between increasing scales and decreasing model refinements (though modelling objectives also show through the chosen spatial and temporal subscales). Then flow typology appears a secondary but important determinant in the choice of model refinement. This finding is confirmed by the discriminating values of several dimensionless numbers, which prove preferential associations between model refinements and flow typologies. This review is intended to help modellers in positioning their choices with respect to the most frequent practices, within a generic, normative procedure possibly enriched by the community for a larger, comprehensive and updated image of modelling strategies.

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