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.

Fairing Evaluation Based on Numerical Simulation

2012 ◽  
Author(s):  
Juan P. Pontaza ◽  
Mohan Kotikanyadanam ◽  
Piet Moeleker ◽  
Raghu G. Menon ◽  
Shankar Bhat
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Current Speed ◽  
Full Scale ◽  
Attractive Alternative ◽  
Element Analysis ◽  
Vortex Induced Vibrations ◽  
Helical Strakes ◽  
Computational Fluid Dynamics Cfd ◽  
Viv Suppression

It is well established that strakes are effective at suppressing vortex-induced vibrations (VIV). Fairings are an attractive alternative to helical strakes, because they are a low drag VIV suppression solution. The paper presents an evaluation of a fairing design, based on numerical simulations — to be complemented at a later stage with current tank testing. This paper documents the computational fluid dynamics (CFD) and finite element analysis (FEA) of the evaluation: (1) 3-D CFD in the laboratory scale: 4.5 inch pipe, 3 ft/s current speed, (2) 3-D CFD in the full scale: 14 inch riser, 4 knots current speed, and (3) 3-D FEA of the full-scale fairing module latching mechanism, under service loads corresponding to 4 knots current speed. The analysis results show that the fairing design (1) is effective at suppressing VIV, (2) yields a low drag coefficient (0.52 at Re ∼ 106), and (3) its latching mechanism is adequate for use in calm sea states with 4 knots current speeds.

Simulation of an Effect of a Baffle Length on the Power Consumption in an Agitated Vessel

2008 ◽  
Vol 4 (2) ◽  
Author(s):  
Palani Sivashanmugam ◽  
S. Prabhakaran
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cfd Simulation ◽  
Turbulence Modeling ◽  
Fluid Flows ◽  
Power Number ◽  
Food Industries ◽  
Agitated Vessel ◽  
Computational Fluid Dynamics Cfd ◽  
Miscible Liquids

Agitated vessels are often used for homogenization of the miscible liquids in chemical, biochemical, and food industries. Computational fluid dynamics (CFD) is a useful tool for studying fluid flows, including those of mixing systems. It is particularly powerful where the ability exists to corroborate model results with available data. The CFD simulation was carried out for Rushton and Smith turbines agitators. The standard k-? model has been used for turbulence modeling. The data obtained by simulation are matching with the literature experimental value for standard baffle with the discrepancy of less than +_4.5% for power number. The simulated results for agitated vessel with short baffle (non-standard) are agreeing with the literature values within plus or minus 5% for Power Number.

CFD Analysis of Vortex-Induced Motions of Bare and Straked Cylinders in Currents

2005 ◽  
Author(s):  
K. P. Thiagarajan ◽  
Y. Constantinides ◽  
L. Finn
Keyword(s):  
Turbulence Modeling ◽  
Equations Of Motion ◽  
Transverse Displacement ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Hexahedral Elements ◽  
Helical Strakes ◽  
Truss Spar ◽  
Uniform Currents ◽  
Tank Geometry

It is widely acknowledged that the use of helical strakes for mitigation of vortex-induced motions (VIM) of surface piercing cylinders, such as spar platforms, is only partially effective. Using computational fluid dynamics tools, we compare the oscillation characteristics of a bare cylinder and a straked cylinder in uniform currents. Our model comprised of a straked cylinder with diameter of 0.741 m, aspect ratio of 1:1.9 and three helical strakes of height 13% of cylinder diameter. This geometry corresponds to the hard tank geometry of a scaled truss spar model known to exhibit VIM in tow tank testing. In the CFD simulations the cylinder is moored with linear springs to provide a range of reduced velocities. The fluid domain is made of an unstructured grid comprising of hexahedral elements. Fluid structure interaction utilizes grid stretching and a user defined function for solving the equations of motion. Turbulence modeling uses Detached Eddy Simulation (DES) and the boundary layer is modeled using a wall function with a surface roughness of 0.0003 m. Reynolds numbers are in the range of 50,000 to 100,000. Results for straked cylinder compares reasonably with published results, but under-predicts the peak response. In comparing with corresponding results for a bare cylinder without strakes, the spectral features of the transverse displacement show variations, which are found to be due to the spoiling effect of the strakes.

CFD Simulation for Vortex Induced Motions of a Multi-Column Floating Platform

2013 ◽  
Author(s):  
Jaime Hui Choo Tan ◽  
Allan Magee ◽  
Jang Whan Kim ◽  
Yih Jeng Teng ◽  
NorBahrain Ahmad Zukni
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Research Effort ◽  
Model Tests ◽  
Floating Platform ◽  
Time Step ◽  
Time Step Size ◽  
Standard Design ◽  
Computational Fluid Dynamics Cfd ◽  
Floating Platforms

The potential of vortex induced motion (VIM) in multi-column floating platforms such as semi-submersibles and tension leg platforms (TLPs) is well-acknowledged although the industry guidelines for design for VIM are not comprehensive and more research effort is required. Significant VIM in multi-column floating platforms will affect the fatigue life of the steel catenary risers and must be quantified and sometimes reduced. Industry-standard design tools used for drag estimation based on model tests of fixed structures may not accurately reflect the effects of drag augmentation due to VIM. Model tests and Computational Fluid Dynamics (CFD) analysis are feasible methods to investigate VIM, with the latter being more resource-efficient, provided sufficient benchmarking has been carried out to ensure reliable results. Subsequent to the model tests and preliminary Computational Fluid Dynamics (CFD) simulations done for a multi-column floating platform [1, 2], further CFD analyses for the VIM of the floating platform have been carried out using improved simulation techniques with a commercial software. Good agreement between model test results and CFD calculations for VIM of a multi-column floating platform is observed. Sensitivity of CFD results to the modeling assumptions such as mesh size and density, time-step size and different turbulence models is presented.

VIV Prediction of a Truss Spar Pull-Tube Array Using CFD

2011 ◽  
Author(s):  
Yiannis Constantinides ◽  
Weiwei Yu ◽  
Samuel Holmes
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Structural Model ◽  
Full Scale ◽  
Complex Flows ◽  
Single Cylinder ◽  
Structure Interaction ◽  
Cylinder Arrays ◽  
Truss Spar ◽  
Computational Fluid Dynamics Cfd

Complex flows through cylinder arrays, such as the case of pull-tubes located in the truss section of a truss spar, are very difficult to describe and analyze. It is especially difficult to predict and correct Vortex Induced Vibration (VIV) response using traditional tools that were developed to analyze single cylinder rather than arrays of cylinders. Computational Fluid Dynamics (CFD) offers the designer the ability to properly analyze these complex problems and increase the reliability of his design. In this study, a full scale truss spar with pull-tubes is modeled using CFD coupled with an FEA structural model of the pull-tubes for a fluid-structure interaction (FSI) computation. The VIV response of the pull-tubes is predicted and analyzed for different current headings and speeds.

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’.

CFD Simulation of Truss Spar Vortex-Induced Motion

2006 ◽  
Author(s):  
Sampath Atluri ◽  
John Halkyard ◽  
Senu Sirnivas
Keyword(s):  
Cfd Simulation ◽  
Turbulence Modeling ◽  
General Purpose ◽  
Scale Model ◽  
Cfd Simulations ◽  
Model Experiments ◽  
Helical Strakes ◽  
Induced Motion ◽  
Truss Spar ◽  
Hydrodynamic Effects

Helical strakes are used to suppress the Vortex-Induced Motion of Truss Spars. Model experiments have demonstrated the efficiency of strakes in the Truss Spar design but also indicate that the VIM response is sensitive to the details of strake design and placement of appurtenances around the Spar hull. It is desirable to study these hydrodynamic effects using CFD. The following paper is a continuation of some of the earlier CFD simulations on this subject (see, J. Halkyard, et al., “Benchmarking of Truss Spar Vortex-Induced Motions Derived from CFD with Experiments”, Proceedings of OMAE’05). This paper in particular deals with the effect of holes in the strakes and appurtenances and their placement. All the simulations were done at model scale (1:40 scale model of an actual Truss Spar design) to compare the motions with experimental results. Mesh sensitivity and turbulence modeling issues are also discussed. Calculations were done using general purpose CFD code Acusolve™.

LBE in the Framework of Computational-Fluid Dynamics

2018 ◽  
Author(s):  
Sauro Succi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Scheme ◽  
General Framework ◽  
The Past ◽  
Computational Fluid Dynamics Cfd ◽  
Made In

This chapter outlines the main properties of LB as a numerical scheme within the general framework of computational fluid dynamics (CFD). The matter has witnessed significant developments in the past decade, and even though the bottomline picture of LB as a very effective numerical scheme stands intact, a number of assessments made in the previous book need some revision. Since the matter is fairly technical, only general notions shall be discussed, leaving in-depth details to the original literature.

Numerical Study and Optimization of Air Flow and Thermal Behavior Inside a Typical Cold Room Loaded With Agricultural Produce

2013 ◽  
Author(s):  
Abhijith Balakrishna ◽  
Wilson Lawrence
Keyword(s):  
Fluid Dynamics ◽  
Thermal Management ◽  
Turbulence Modeling ◽  
Numerical Study ◽  
Air Flow ◽  
Front Wall ◽  
Research Activity ◽  
Agricultural Produce ◽  
Cold Room ◽  
Computational Fluid Dynamics Cfd

This work is part of a research activity aiming to improve and optimize air flow and temperature distribution inside a refrigerated cold room. An improved flexible air duct design inside the cold room is studied for uniform air flow and minimum temperature gradient inside the cold room. The present study investigates on various flexible air duct designs inside the cold room to provide better thermal management to improve the shelf life of the produce. In this study, the most commonly used refrigerated cold room is considered with inlet and outlet sections placed in the front wall of the room. The numerical modeling of airflow was performed using the computational fluid dynamics (CFD) code Fluent and turbulence modeling with standard k–ε model.

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