Hydrodynamic Response of Buoy Form Spar With Heave Plate Near Free Surface

2021 ◽  
Author(s):  
Pooja Hegde ◽  
S. Nallayarasu
Keyword(s):  
Fluid Dynamics ◽  
Free Surface ◽  
Hydrodynamic Characteristics ◽  
The Past ◽  
Damping Characteristics ◽  
Free Decay ◽  
Hydrodynamic Response ◽  
Computational Fluid Dynamics Cfd ◽  
Heave Plate ◽  
Pitch Damping

Abstract Hydrodynamic response of spar with appendages such as heave plate has been investigated in the past, mostly attached at the bottom of the spar. The effect of geometry and appendages on the hydrodynamic response of spar has been investigated in this article. A curved neck form with a heave plate near the free surface is proposed as an energy dissipation device for both heave and pitch responses. Numerical simulation using Computational Fluid Dynamics (CFD) is used for capturing the flow around the curved neck with heave plate and corresponding damping characteristics. CFD free decay simulations have been carried out to obtain heave and pitch damping and were noted to be higher than the conventional spar with heave plate at the bottom. Comparison of the proposed geometry and heave plate at the free surface with a conventional heave plate at the bottom of the spar has been made, and significant changes to the response and hydrodynamic characteristics have been noted. It is observed that the buoy form spar combined with the heave plate located near the surface (within 10% of the draft) helps dissipate energy and thus reduce the heave response.

Effect of Bilge Radius and Bilge Keel Height on Roll Damping Performance of Floating Structures

2021 ◽  
Author(s):  
Chang Seop Kwon ◽  
Joo-Sung Kim ◽  
Hyun Joe Kim
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Kinetic Energy ◽  
Floating Body ◽  
Rectangular Section ◽  
Roll Damping ◽  
Floating Structures ◽  
Free Decay ◽  
Computational Fluid Dynamics Cfd ◽  
Bilge Keel

Abstract A round bilge with a bilge keel structure is a key element which can alleviate roll motions of ships and floating structures by transferring the roll momentum of a floating body into the kinetic energy of water. This study presents a practical guide to properly designing a bilge radius and bilge keel height of a barge-shaped and tanker-shaped FPSOs. A parametric study to figure out the effect of bilge radius and bilge keel height on the roll damping performance is conducted through a series of numerical roll free decay simulations based on Computational Fluid Dynamics (CFD). The bilge radius is normalized by the half breadth of ship, and the bilge keel height is normalized by the maximum bilge keel height which is limited by the molded lines of a side shell and bottom shell. In addition, it is investigated to identify how the roll damping performance of a rectangular section differs from the result of a typical round bilge section with maximum available bilge keel height.

Truss Spar Vortex Induced Motions: Benchmarking of CFD and Model Tests

2006 ◽  
Author(s):  
John Halkyard ◽  
Sampath Atluri ◽  
Senu Sirnivas
Keyword(s):  
Fluid Dynamics ◽  
Best Practices ◽  
Turbulence Modeling ◽  
Production Systems ◽  
Model Tests ◽  
The Past ◽  
Helical Strakes ◽  
Truss Spar ◽  
Computational Fluid Dynamics Cfd ◽  
Riser Design

Spar production systems are subject to Vortex Induced Motions (VIM) which may impact mooring and riser design. Helical strakes are employed to mitigate VIM. Model tests are typically required to validate the performance of the strakes. This paper will report on the results of benchmarking studies that have been conducted over the past few years to compare model tests with computational fluid dynamics (CFD). The paper discusses comparisons of CFD with model tests, “best practices” for the use of CFD for these classes of problems and issues related to turbulence modeling and meshing of problems at large Reynold’s numbers. This work is ongoing.

scholarly journals Investigations on Large-Scale Geometric Roughness Elements in Open Channels with Different Heights

2021 ◽  
Vol 28 (1) ◽  
pp. 07-14
Author(s):  
Iman A. Alwan ◽  
Riyadh Z. Azzubaidi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Free Surface ◽  
Large Scale ◽  
Open Channel ◽  
Control Case ◽  
Hydraulic Characteristics ◽  
Roughness Elements ◽  
Computational Fluid Dynamics Cfd ◽  
Effective Case

Large-scale geometric roughness elements is one of the solutions that is used to protect openchannels from erosion. It is use to change the hydraulic characteristics of the flow. It may be concrete blocksor large stone placed at the bed of the channel to impose more resistance in the bed. The height of theseroughness elements is an important parameter that can affect the hydraulic characteristics of the flow. Usinga series of tests of T-shape roughness elements at three different heights, 3, 4.5, and 6cm, arranged in thefully rough configuration in order to investigate the velocity distributions along the flume. ANSYSParametric Design Language, APDL, and Computational Fluid Dynamics, CFD, were used to simulate theflow in an open channel with roughness elements. This simulation helps to find the best height of roughnesselements that can be used to change the hydraulic characteristics of the flow. The results showed that thevelocity values are decreased near the bed by about 61%, 58%, and 64% in case of 3cm, 4.5cm, and 6cmroughness heights consequently compared with the velocity of the control case. The velocity values areincreased near the free surface by about 32% and 19% in case of roughness elements height 6cm comparedwith 3cm and 4.5cm roughness heights respectively. The case of 6cm roughness height is considered to bethe effective case for decreasing the velocity values near the bed of the flume.

Virtual Model Basin for Resistance, Maneuvering, and Seakeeping: A RANS CFD Based Approach

2007 ◽  
Author(s):  
Balasubramanyam Sasanapuri ◽  
Viraj Suresh Shirodkar ◽  
Wesley Wilson ◽  
Samir Kadam ◽  
Shin Hyung Rhee
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Free Surface ◽  
Water Resistance ◽  
Primary Objective ◽  
Navier Stokes ◽  
Theory Method ◽  
Virtual Model ◽  
Calm Water ◽  
Computational Fluid Dynamics Cfd

A Virtual Model Basin (VMB) is developed based on a Computational Fluid Dynamics (CFD) approach to solving the Reynolds Averaged Navier-Stokes (RANS) equations along with the Volume of Fluid (VOF) method for predicting the free surface. The primary objective of this work is to develop methodologies for the VMB and to demonstrate the capabilities for a generic multi-hull ship geometry. The VMB is used to simulate various model basin tests for steady resistance, maneuvering and seakeeping. For a generic catamaran hull configuration, the methodologies are used for solving these problems and the results are discussed in this paper. VMB results are compared with the results of a benchmarked potential flow theory method for calm water resistance.

Numerical Simulation of the Fixed Barge Barge Interaction Under Irregular Wave Using HOS-StarCCM+ Coupling Tool With Experiment Validation

2021 ◽  
Author(s):  
Yali Zhang ◽  
Haihua Xu ◽  
Harrif Santo ◽  
Kie Hian Chua ◽  
Yun Zhi Law ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Free Surface ◽  
Potential Flow ◽  
Computational Domain ◽  
Cfd Model ◽  
Flow Models ◽  
Irregular Wave ◽  
Computational Fluid Dynamics Cfd ◽  
Wave Conditions

Abstract The interaction between two side-by-side floating vessels has been a subject of interest in recent years due floating liquefied natural gas (FLNG) developments. The safety and operability of these facilities are affected by the free-surface elevation in the narrow gap between the two vessels as well as the relative motions between the vessels. It is common practice in the industry to use potential flow models to estimate the free-surface responses in the gap under various wave conditions. However, it is well-known that any potential flow models require calibration of viscous damping, and model tests are carried out to provide a platform to calibrate the potential flow models. To improve beyond the potential flow models, Computational Fluid Dynamics (CFD) models will be required. However, the large computational efforts required render the conventional CFD approaches impractical for simulations of wave-structure interactions over a long duration. In this paper, a developed coupled solver between potential flow and Computational Fluid Dynamics (CFD) model is presented. The potential flow model is based on High-Order Spectral method (HOS), while the CFD model is based on fully nonlinear, viscous and two phase StarCCM+ solver. The coupling is achieved using a forcing zone to blend the outputs from the HOS into the StarCCM+ solver. Thus, the efficient nonlinear long time simulation of arbitrary input wave spectrum by HOS can be transferred to the CFD domain, which can reduce the computational domain and simulation time. In this paper, we make reference to the model experiments conducted by Chua et al. (2018), which consist of two identical side-by-side barges of 280 m (length) × 46 m (breadth) × 16.5 m (draught) tested in regular and irregular wave conditions. Our intention is to numerically reproduce the irregular wave conditions and the resulting barge-barge interactions. We first simulate the actual irregular wave conditions based on wave elevations measured by the wave probes using the HOS solver. The outputs are subsequently transferred to the CFD solver through a forcing zone in a 2D computational domain for comparison of the irregular wave conditions without the barges present. Subsequently, a 3D computational domain is set up in the CFD with fixed side-by-side barges modelled, and the interaction under irregular waves is simulated and compared with the experiments. We will demonstrate the applicability of the HOS-StarCCM+ coupling tool in terms of accuracy, efficiency as well as verification and validation of the results.

scholarly journals Investigation of the Effect of Ski Jump on the Flow Dynamics around Generic Aircraft Carrier

2021 ◽  
Vol 71 (2) ◽  
pp. 296-303
Author(s):  
Rahul Thakur ◽  
K. Vignesh Kumar
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Degrees Of Freedom ◽  
Flow Dynamics ◽  
Aircraft Carrier ◽  
Six Degrees Of Freedom ◽  
The Past ◽  
Turbulent Airflow ◽  
Computational Fluid Dynamics Cfd ◽  
Flight Deck

The landing operation on an aircraft carrier is a complicated and risky process. Unlike land-based operations, the landing area available on carriers is in continuous motion in all the six degrees of freedom. The ski jump, flight deck, hull, and superstructure of the carrier interact with the oncoming wind’s flow-field which creates a turbulent airflow behind the carrier. This ‘burble effect’ is very dangerous and has caused various mishaps in the past. To complement the work being undertaken at IIT Delhi to study the flow dynamics in the carrier environment, the present study investigates the effect of ski jump and superstructure on the flow around the generic aircraft carrier (GAC). Computational fluid dynamics (CFD) studies are undertaken to simulate the airwake and establish a baseline with the ski jump. Subsequently, further studies are carried out to analyse the sensitivity of the wake to changes in carrier geometry. The introduction of the ski generates a major proportion of turbulence encountered in the aft by the approaching pilot. This is reduced significantly by optimising ski jump geometry in various ways.

scholarly journals Numerical Analysis of Semi-Tangential Ogive Bullet

2021 ◽  
Vol 9 (8) ◽  
pp. 1869-1883
Author(s):  
Avinash T
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Analysis ◽  
Computer Aided Design ◽  
Steady Increase ◽  
The Past ◽  
Computer Aided ◽  
Parametric Studies ◽  
Computational Fluid Dynamics Cfd ◽  
Aided Design

Abstract: The objective of the present study is to design and analyze semi-tangential ogive bullets using simulatation software such as Computer-aided design & Computational Fluid Dynamics (CFD). It is observed that been a quite steady increase in the bullet research design in the past few decades. The nose section of ballistic bullet is the most important part of the design process. Hence design optimizations are achieved by adjusting the bullet's form to improve precision and stability by reducing its drag force. CFD is the study used to verify the findings. Since provides most accurate results. It is observed that present study optimizes the behavior of the at M= 2.5. This present work shows the flow of air around the bullet surface providing pressure & velocity contours at every segment. The Various parametric studies over bullet model are drag co-efficient, ballistic coefficient and turbulence viscosity are plotted’.

scholarly journals Computational Fluid Dynamics Study of Swimmer's Hand Velocity, Orientation, and Shape: Contributions to Hydrodynamics

2013 ◽  
Vol 2013 ◽  
pp. 1-14 ◽  
Author(s):  
Milda Bilinauskaite ◽  
Vishveshwar Rajendra Mantha ◽  
Abel Ilah Rouboa ◽  
Pranas Ziliukas ◽  
Antonio Jose Silva
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fluid Flow ◽  
Steady State ◽  
Drag Force ◽  
3D Models ◽  
Hydrodynamic Characteristics ◽  
Front Crawl ◽  
Drag Forces ◽  
Computational Fluid Dynamics Cfd

The aim of this paper is to determine the hydrodynamic characteristics of swimmer’s scanned hand models for various combinations of both the angle of attack and the sweepback angle and shape and velocity of swimmer's hand, simulating separate underwater arm stroke phases of freestyle (front crawl) swimming. Four realistic 3D models of swimmer's hand corresponding to different combinations of separated/closed fingers positions were used to simulate different underwater front crawl phases. The fluid flow was simulated using FLUENT (ANSYS, PA, USA). Drag force and drag coefficient were calculated using (computational fluid dynamics) CFD in steady state. Results showed that the drag force and coefficient varied at the different flow velocities on all shapes of the hand and variation was observed for different hand positions corresponding to different stroke phases. The models of the hand with thumb adducted and abducted generated the highest drag forces and drag coefficients. The current study suggests that the realistic variation of both the orientation angles influenced higher values of drag, lift, and resultant coefficients and forces. To augment resultant force, which affects swimmer's propulsion, the swimmer should concentrate in effectively optimising achievable hand areas during crucial propulsive phases.

scholarly journals Estimation of the Motion Performance of a Light Buoy Adopting Ecofriendly and Lightweight Materials in Waves

2020 ◽  
Vol 8 (2) ◽  
pp. 139 ◽  
Author(s):  
Se-Min Jeong ◽  
Bo-Hun Son ◽  
Chang-Yull Lee
Keyword(s):  
Fluid Dynamics ◽  
Wave Motion ◽  
Viscous Damping ◽  
Motion Simulation ◽  
Incoming Wave ◽  
Damping Coefficients ◽  
Free Decay ◽  
Computational Fluid Dynamics Cfd ◽  
Motion Performance ◽  
Decay Tests

In this study, the methods and results of numerical simulations to estimate the motion performance of a newly developed lightweight light buoy in waves and to check the effect of conceptually developed appendages on that performance were introduced. The results from a potential-based motion analysis with viscous damping coefficients obtained from free decay tests using computational fluid dynamics (CFD) and those obtained from wave motion simulation using CFD were compared. From these results, it was confirmed that viscous damping should be considered when the frequency of an incoming wave is close to the natural frequency of the buoy. It was estimated that the pitch and heave motions of the light buoy became smaller when the developed appendages were adopted. Although the quantitative superiority of the appendages was different, the qualitative superiority was similar between both results.

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