URANS PREDICTION OF THE SLAMMING COEFFICIENTS FOR PERFORATED PLATES DURING WATER ENTRY

2021 ◽  
Vol 160 (A1) ◽  
Author(s):  
W Zhang ◽  
S Chai ◽  
H Nguyen ◽  
Y Jin
Keyword(s):  
Free Surface ◽  
Negative Impact ◽  
Water Entry ◽  
Navier Stokes ◽  
Width Ratio ◽  
Experimental Measurements ◽  
Perforated Plates ◽  
Trapped Air ◽  
Length Width ◽  
Surface Profiles

The slamming coefficients for perforated plates of various perforation ratios and layout configurations were predicted using Unsteady Reynolds-Averaged Navier-Stokes (URANS) solver STAR-CCM+. The numerical model was validated by comparing with experimental measurements of slamming coefficient for a circular cylinder. The slamming coefficients and free surface profiles of perforated plates were then predicted at full-scale. It was found the air compressibility plays an important role by studying flat plate water entry phenomena. For perforated plates with small gap length/width ratios, the ability of the trapped air to evacuate through the space between the bottom of the plate and free surface is similar. For perforated plates with different gap number at a fixed perforation ratio, the slamming coefficient is increased with the increase in gap length/width ratio. However, a further increase in length/width ratio may impose a negative impact on the escape of trapped air due to the increase of gap number.

URANS Prediction of the Slamming Coefficients for Perforated Plates During Water Entry

2018 ◽  
Vol Vol 160 (A1) ◽  
Author(s):  
W Zhang ◽  
S Chai ◽  
H Nguyen ◽  
Y Jin
Keyword(s):  
Free Surface ◽  
Negative Impact ◽  
Water Entry ◽  
Navier Stokes ◽  
Width Ratio ◽  
Experimental Measurements ◽  
Perforated Plates ◽  
Trapped Air ◽  
Length Width ◽  
Surface Profiles

The slamming coefficients for perforated plates of various perforation ratios and layout configurations were predicted using Unsteady Reynolds-Averaged Navier-Stokes (URANS) solver STAR-CCM+. The numerical model was validated by comparing with experimental measurements of slamming coefficient for a circular cylinder. The slamming coefficients and free surface profiles of perforated plates were then predicted at full-scale. It was found the air compressibility plays an important role by studying flat plate water entry phenomena. For perforated plates with small gap length/width ratios, the ability of the trapped air to evacuate through the space between the bottom of the plate and free surface is similar. For perforated plates with different gap number at a fixed perforation ratio, the slamming coefficient is increased with the increase in gap length/width ratio. However, a further increase in length/width ratio may impose a negative impact on the escape of trapped air due to the increase of gap number.

Mechanics of a Free-Surface Liquid Film Flow

1987 ◽  
Vol 54 (4) ◽  
pp. 951-954 ◽  
Author(s):  
Cyrus K. Aidun
Keyword(s):  
Differential Equation ◽  
Free Surface ◽  
Film Flow ◽  
Navier Stokes ◽  
Experimental Measurements ◽  
Navier Stokes Equation ◽  
Higher Order Terms ◽  
Liquid Film Flow ◽  
Surface Liquid ◽  
Similar Equation

The mechanics of a free surface viscous liquid curtain flowing steadily between two vertical guide wires under the influence of gravity is investigated. The Navier-Stokes equation is integrated over the film thickness and an integro-differential equation is derived for the average film velocity. An approximate nonlinear differential equation, attributed to G. I. Taylor, is obtained by neglecting the higher order terms. An analytical solution is obtained for a similar equation which neglects the surface tension effects and the results are compared with the experimental measurements of Brown (1961).

scholarly journals Numerical Modeling and Simulation of Wave Impact of a Circular Cylinder during the Submergence Process

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Xiaozhou Hu ◽  
Yiyao Jiang ◽  
Daojun Cai
Keyword(s):  
Free Surface ◽  
Circular Cylinder ◽  
Ocean Waves ◽  
Navier Stokes ◽  
Wave Load ◽  
Wave Impact ◽  
Rans Equations ◽  
Wave Slamming ◽  
Surface Profiles ◽  
Numerical Wave

Wave slamming loads on a circular cylinder during water entry and the subsequence submergence process are predicted based on a numerical wave load model. The wave impact problems are analyzed by solving Reynolds-Averaged Navier-Stokes (RANS) equations and VOF equations. A finite volume approach (FV) is employed to implement the discretization of the RANS equations. A two-dimensional numerical wave tank is established to simulate regular ocean waves. The wave slamming problems are investigated by deploying a circular cylinder into waves with a constant vertical velocity. The present numerical method is validated using other numerical or theoretical results in accordance with varying free surface profiles when a circular cylinder sinks in calm water. A numerical example is given to show the submergence process of the circular cylinder in waves, and both free surface profiles and the pressure distributions on the cylinder of different time instants are obtained. Time histories of hydrodynamic load on the cylinder during the submergence process for different wave impact angles, wave heights, and wave periods are obtained, and results are analyzed in detail.

scholarly journals STUDY ON WATER ENTRY PROBLEM USING A LEVEL-SET IMMERSED BOUNDARY METHOD

2014 ◽  
Vol 34 ◽  
pp. 1460376
Author(s):  
WEI BAI ◽  
CHENGZHONG HUO
Keyword(s):  
Free Surface ◽  
Level Set ◽  
Immersed Boundary Method ◽  
Surface Profile ◽  
Water Entry ◽  
Navier Stokes ◽  
Immersed Boundary ◽  
Interface Evolution ◽  
Boundary Method ◽  
Moving Bodies

Water entry of a solid through the free surface is a persisting field of research in ship hydrodynamics applications. Indeed, the knowledge of pressure forces acting on structures is necessary to ensure the verification of safety criteria in the design and operation. However, in water entry problems, jets can be generated, thus an effective numerical model is needed to capture this complicated breaking water surface. In this paper, the level set method is adopted, which has been shown to be capable of capturing interface evolution when the topological change of shape is extremely large, or merging, breaking and pinching occur. Moreover, the incorporation of an immersed boundary method with this free surface capture scheme implemented in a Navier-Stokes solver allows the interaction between fluid flow with free surface and moving bodies of almost arbitrary shape to be modeled. The developed Level-Set Immersed Boundary Method is applied to simulate the water entry of a rectangular body with different velocities into the still water. The complicated surface profile, velocity field and pressure are obtained. The simulation is also carried out for the same body exiting the water, and some preliminary results are presented.

Numerical Invertigation of Water Entry of a Subsea Module With Deflated Cavity Shells

2020 ◽  
Author(s):  
Yingfei Zan ◽  
Ruinan Guo ◽  
Lihao Yuan ◽  
Fuxiang Huang ◽  
Dongchun Kang
Keyword(s):  
Numerical Simulation ◽  
Free Surface ◽  
Flow Field ◽  
Stokes Equations ◽  
Water Entry ◽  
Hydrodynamic Forces ◽  
Operating Conditions ◽  
Frame Structure ◽  
Navier Stokes ◽  
Navier Stokes Equations

Abstract In subsea installation operations, the hydrodynamic forces on the subsea module are important considerations when designing the structure and choosing slings. In this paper, the hydrodynamic forces and flow field of a subsea module with deflated cavity shells during forced water entry operation were investigated numerically. The numerical simulation was carried out based on Reynolds-averaged Navier–Stokes equations, with a constant lowering velocity of the module. The results of the numerical simulation were validated by experimental data and they showed good agreement. The relationship between hydrodynamic forces and draft was presented. Furthermore, the slamming positions, free surface variation, pressure variation in deflated cavity shells, slamming coefficient and the influence of holes were studied based on flow field scenes. It was found that the hydrodynamic forces varied with draft non-linearly. Moreover, the change of draft altered the form of the free surface due to the complex steel frame structure of deflated cavity shells. The present study can be further extended to assess the operating conditions of lifting operations and to advise on the design of the subsea module.

scholarly journals Diversity of Pod Shape in Pisum

Diversity ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 203
Author(s):  
Thomas Henry Noel Ellis ◽  
Julie M. I. Hofer ◽  
Eleni Vikeli ◽  
Michael J. Ambrose ◽  
Paola Higuera-Poveda ◽  
...  
Keyword(s):  
Allelic Variation ◽  
Size Variation ◽  
Width Ratio ◽  
Negative Regulators ◽  
Wide Range ◽  
Yield Determination ◽  
Organ Specific ◽  
Length Width ◽  
End Use ◽  
Pod Length

The seed-containing pod is the defining structure of plants in the legume family, yet pods exhibit a wide range of morphological variation. Within a species pod characters are likely to be correlated with reproductive strategy, and within cultivated forms will correspond to aspects of yield determination and/or end use. Here variation in pod size, described as pod length: pod width ratio, has been analyzed in pea germplasm represented by 597 accessions. This pod size variation is discussed with respect to population structure and to known classical pod morphology mutants. Variability of the pod length: width ratio can be explained by allelic variation at two genetic loci that may correspond to organ-specific negative regulators of growth.

Influences of Recess Geometry and Restrictor Dimension on Flow Patterns and Pressure Distribution of Hydrostatic Bearings

2007 ◽  
Author(s):  
Cheng-Hsien Chen ◽  
Yuan Kang ◽  
Yeon-Pun Chang ◽  
De-Xing Peng ◽  
Ding-Wen Yang
Keyword(s):  
Pressure Distribution ◽  
Stokes Equations ◽  
Flow Patterns ◽  
Lubricant Film ◽  
Navier Stokes ◽  
Width Ratio ◽  
Navier Stokes Equations ◽  
Hydrostatic Bearing ◽  
Lubricant Flow ◽  
Land Width

This paper studies the influences of recess geometry and restrictor dimensions on the flow patterns and pressure distribution of lubricant film, which are coupled effects of hybrid characteristics of a hydrostatic bearing. The lubricant flow is described by using the Navier-Stokes equations. The Galerkin weighted residual finite element method is applied to determine the lubricant velocities and pressure in the bearing clearance. The numerical simulations will evaluate the effects of the land-width ratio and restriction parameter as well as the influence of modified Reynolds number and the jet-strength coefficient on the flow patterns in the recess and pressure distribution in lubricant film. On the basis of the simulation drawn from this study, the simulated results are expected to help engineers make better use of the design of hydrostatic bearing and its restrictors.

Simulation of the Gap Resonance Between Two Rectangular Barges in Regular Waves by a Free Surface Viscous Flow Solver

2013 ◽  
Author(s):  
B. Elie ◽  
G. Reliquet ◽  
P.-E. Guillerm ◽  
O. Thilleul ◽  
P. Ferrant ◽  
...  
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Viscous Flow ◽  
Stokes Equations ◽  
Resonance Phenomenon ◽  
Navier Stokes ◽  
Regular Waves ◽  
Navier Stokes Equations ◽  
Flow Solver ◽  
Gap Resonance

This paper compares numerical and experimental results in the study of the resonance phenomenon which appears between two side-by-side fixed barges for different sea-states. Simulations were performed using SWENSE (Spectral Wave Explicit Navier-Stokes Equations) approach and results are compared with experimental data on two fixed barges with different headings and bilges. Numerical results, obtained using the SWENSE approach, are able to predict both the frequency and the magnitude of the RAO functions.

Meshing Method of High Precision FEM in Large Complex Structural Simulations

2012 ◽  
Vol 195-196 ◽  
pp. 701-704
Author(s):  
Yan Hua Xue ◽  
Zhi Guang Wang ◽  
Xiao Hong Li ◽  
Xin Jiang
Keyword(s):  
Finite Element ◽  
Complex Structure ◽  
Width Ratio ◽  
Two Dimensional ◽  
Element Analysis ◽  
Large Complex ◽  
Mesh Density ◽  
Length Width ◽  
Complex Structural ◽  
Dimensional Element

Shing is playing an important role in the large complex structural FEM simulations; it has a direct effect on calculating precision of structural simulations. For increasing the calculation accuracy and analysis accuracy of complex structure, the finite element meshing problems is proposed on the finite element analysis of large complicated structures. The effects caused by element type, mesh density and intergradations on calculating precision are studied and discussed. A research argues that with length-width ratio of 1~2 and length-thickness ration of 1.5~4.5 of two-dimensional rectangular element, the quality of meshing method of two-dimensional element is above normal. As the height of one-dimensional element is equal to the sum of reinforcing rib height of outer panel and half the thickness of panel, more accurate results can be obtained.

Investigation of the stability of boundary layers by a finite-difference model of the Navier—Stokes equations

1976 ◽  
Vol 78 (2) ◽  
pp. 355-383 ◽  
Author(s):  
H. Fasel
Keyword(s):  
Finite Difference ◽  
Stability Theory ◽  
Stokes Equations ◽  
Time Dependent ◽  
Linear Stability Theory ◽  
Navier Stokes ◽  
Experimental Measurements ◽  
Navier Stokes Equations ◽  
The Stability ◽  
Small Periodic

The stability of incompressible boundary-layer flows on a semi-infinite flat plate and the growth of disturbances in such flows are investigated by numerical integration of the complete Navier–;Stokes equations for laminar two-dimensional flows. Forced time-dependent disturbances are introduced into the flow field and the reaction of the flow to such disturbances is studied by directly solving the Navier–Stokes equations using a finite-difference method. An implicit finitedifference scheme was developed for the calculation of the extremely unsteady flow fields which arose from the forced time-dependent disturbances. The problem of the numerical stability of the method called for special attention in order to avoid possible distortions of the results caused by the interaction of unstable numerical oscillations with physically meaningful perturbations. A demonstration of the suitability of the numerical method for the investigation of stability and the initial growth of disturbances is presented for small periodic perturbations. For this particular case the numerical results can be compared with linear stability theory and experimental measurements. In this paper a number of numerical calculations for small periodic disturbances are discussed in detail. The results are generally in fairly close agreement with linear stability theory or experimental measurements.

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