A Joint-Industry Effort to Develop and Verify CFD Modeling Practice for Predicting Hydrodynamic Coefficients on Bare Riser Surfaces

2021 ◽  
Author(s):  
Hyunchul Jang ◽  
Madhusuden Agrawal ◽  
Dongwhan Lee ◽  
Wei Xu ◽  
Jerry Huang ◽  
...  
Keyword(s):  
Forced Oscillation ◽  
Lift Coefficient ◽  
Circular Cross Section ◽  
Cfd Modeling ◽  
First Year ◽  
Cfd Analysis ◽  
Hydrodynamic Coefficients ◽  
Steady Current ◽  
Calm Water ◽  
Modeling Practice

Abstract Hydrodynamic force coefficients are important parameters in design and assessment of marine risers. The hydrodynamic coefficients are widely used for assessing marine riser responses due to floater motion excitation and vortex-induced vibrations (VIV). Traditionally, the hydrodynamic coefficients have been obtained from physical model tests on short rigid riser sections. Recently, the offshore industry has started to use computational fluid dynamics (CFD) analysis for predicting the hydrodynamic coefficients due to the recent advancement of CFD software and high-performance computing capabilities, but a reliable CFD modeling practice is requested for CFD analysis to be a more widely accepted prediction tool in the industry. A joint industry effort has been made for developing and verifying the reliable CFD modeling practice through a working group of the Reproducible Offshore CFD JIP. In the working group, a CFD modeling practice document was written based on existing practices already validated for model test data, and verified by blind validations with three CFD practitioners. The first year works are focused on the bare riser with circular cross-section, and the second year work will be extended to the other riser sections such as staggered buoyancy module and straked riser. This paper presents the working group’s first-year verification activities for a bare riser with circular cross-section. The verification works covers three test problems: 1) stationary simulation in steady current, 2) forced-oscillation in calm water, 3) forced-oscillation in steady current. In the stationary simulation, mean drag coefficient, standard deviation of lift coefficient, and Strouhal numbers are compared. In the forced-oscillation simulation in calm water, the fully-submerged riser section oscillates with a sinusoidal motion, and damping and added mass coefficients are compared. In the forced-oscillation simulation in current, the riser section oscillates in cross-flow direction to the steady current, and lift coefficient and added mass coefficient are compared. By following the modeling practice, the CFD predictions are consistent with each other and close to the model test data for a majority of test cases.

Forced Oscillation Model Tests for Determination of Hydrodynamic Coefficients of Large Subsea Blowout Preventers

2015 ◽  
Author(s):  
Xavier Arino ◽  
Jaap de Wilde ◽  
Massimiliano Russo ◽  
Guttorm Grytøyr ◽  
Michael Tognarelli
Keyword(s):  
Large Scale ◽  
Forced Oscillation ◽  
Model Tests ◽  
Scale Model ◽  
Hydrodynamic Coefficients ◽  
Lumped Mass ◽  
Towing Tank ◽  
Steady Current ◽  
Large Scale Model

Large scale model tests have been conducted in a towing tank facility for the determination of the hydrodynamic coefficients of subsea blowout preventers. A subsea blowout preventer (BOP) is a large, complex device 10–15 [m] tall, weighing 200–450 [ton]. The BOP stack consists of two assemblies, the ‘lower marine riser package’ (LMRP) connected to the riser string and the BOP itself, connected to the wellhead. Together they represent a large lumped mass, which directly influences the natural frequencies and vibration modes of the riser system, particularly those of the BOP-wellhead-casing assembly. Large uncertainties in the estimates of the hydrodynamic coefficients (added mass, lift and drag or damping) result in large uncertainties in the fatigue damage predictions of the riser and wellhead system. The trend toward larger and heavier BOPs, which could place BOP-wellhead-casing oscillation frequencies in the range of wave frequencies, has motivated Statoil and BP to start a new research project on this subject. The project involves a large scale model test for experimental determination of hydrodynamic coefficients. Two different BOP designs were tested in a towing tank at model scale 1:12. The models weighed about 50 [kg] in air and were about 1.2–1.5 [m] tall. A six-degree-of-freedom oscillator was mounted under the carriage of the towing tank for oscillation of the models in different directions. Static tow tests and forced oscillation tests with and in the absence of steady current were carried out. Keulegan-Carpenter (KC) numbers ranged between 0.2 and 2.0, while the Sarpkaya frequency parameter β was in the range from 4,000 to 50,000. The Reynolds numbers of the static tow tests ranged between 50,000 and 150,000. This paper focuses particularly on tests in the surge direction with and in the absence of a steady current. Results indicate that the hydrodynamic coefficients for BOP stacks are quite different from those of simpler geometries like a circular cylinder. In addition, they provide new insight for analytical modeling of global hydrodynamic forces on BOPs in many configurations and scenarios.

scholarly journals Hydrodynamic Coefficients of Simplified Subsea Structures

2018 ◽  
Author(s):  
Fredrik Mentzoni ◽  
Mia Abrahamsen-Prsic ◽  
Trygve Kristiansen
Keyword(s):  
Cross Section ◽  
Significant Interaction ◽  
Hydrodynamic Interaction ◽  
Forced Oscillation ◽  
Large Range ◽  
Circular Cross Section ◽  
Added Mass ◽  
Hydrodynamic Coefficients ◽  
Force Estimation ◽  
Damping Coefficients

Simplified two-dimensional models, representing components of complex subsea structures, are experimentally investigated. Individual as well as combinations of components in different configurations are tested, in order to study the effect of hydrodynamic interaction. The components include porous plates and cylindrical pipes with circular cross-section. Hydrodynamic added mass and damping coefficients, relevant for force estimation during lifting operations, are presented. The coefficients are obtained based on forced oscillation tests for a large range of Keulegan–Carpenter (KC) numbers and forcing periods, and compared to numerical source panel results for the low KC limit, as well as recommendations given by DNV GL, where relevant. Coefficients for all configurations are found to be highly amplitude dependent. Significant interaction effects are found for the assembled structures, causing either reduced or increased total added mass and damping coefficients compared to the super-position of the coefficients for individual members.

Numerical Investigation for Vortex-Induced Vibrations of Steel-Lazy-Wave-Risers: Part II — CFD Study on Long Flexible Riser

2019 ◽  
Author(s):  
Hyunchul Jang ◽  
Jang Whan Kim
Keyword(s):  
Structural Model ◽  
Cfd Simulation ◽  
Forced Oscillation ◽  
Structural Equations ◽  
Model Tests ◽  
Cfd Modeling ◽  
Hydrodynamic Coefficients ◽  
Cfd Simulations ◽  
Oscillation Model ◽  
Water Developments

Abstract Vortex-Induced Vibration (VIV) is one of the main sources of fatigue damage for long slender risers. Typical VIV assessment of risers is conducted using semi-empirical software tools in which the sectional hydrodynamic coefficients are derived from forced oscillation model tests on short rigid risers. The Steel Lazy Wave Riser (SLWR) with buoyancy sections is an attractive concept for improving fatigue performance in deep water developments, but there is limited model test data available for the hydrodynamic coefficients on SLWR’s. In Part I of the present study (Jang & Kim, 2019), CFD simulations are successfully validated against forced-oscillation model tests. In this paper, the feasibility of using CFD simulations for VIV response of a long flexible SLWR has been studied based on the CFD modeling practice developed in Part I. The CFD simulation is coupled with a simple structural model of the riser, and the structural equations of motions are solved via modal analysis. The simulation results capture all excitation frequencies measured from the model tests.

CFD Modeling and Simulation of Aeorodynamic Cooling of Automotive Brake Rotor

2018 ◽  
Vol 09 (01) ◽  
pp. 1750008 ◽  
Author(s):  
Ali Belhocien ◽  
Wan Zaidi Wan Omar
Keyword(s):  
Heat Dissipation ◽  
Surface Film ◽  
Transient State ◽  
Cfd Modeling ◽  
Disc Brake ◽  
Cfd Analysis ◽  
Braking System ◽  
Airflow Distribution ◽  
Ansys Cfx ◽  
Brake Rotor

Braking system is one of the important control systems of an automotive. For many years, the disc brakes have been used in automobiles for the safe retarding of the vehicles. During the braking enormous amount of heat will be generated and for effective braking sufficient heat dissipation is essential. The thermal performance of disc brake depends upon the characteristics of the airflow around the brake rotor and hence the aerodynamics is an important in the region of brake components. A CFD analysis is carried out on the braking system as a case study to make out the behavior of airflow distribution around the disc brake components using ANSYS CFX software. We are interested in the determination of the heat transfer coefficient (HTC) on each surface of a ventilated disc rotor varying with time in a transient state using CFD analysis, and then imported the surface film condition data into a corresponding FEM model for disc temperature analysis.

Study of the Change of Performance of an Elastic Vertical Hydrofoil With Deformation

2014 ◽  
Author(s):  
Alexander Führing ◽  
Subha Kumpaty ◽  
Chris Stack
Keyword(s):  
Water Flow ◽  
Lift Coefficient ◽  
Flow Analysis ◽  
Turbulence Models ◽  
Flow Property ◽  
Performance Data ◽  
Cfd Analysis ◽  
Ansys Fluent ◽  
Drag Forces ◽  
Fluid Flow Analysis

In external and internal fluid flow analysis using numerical methods, most attention is paid to the properties of the flow assuming absolute rigidity of the solid bodies involved. However, this is often not the case for water flow or other fluids with high density. The pressure forces cause the geometry to deform which in turn changes the flow properties around it. Thus, a one-way and two-way Fluid-Structure Interaction (FSI) coupling is proposed and compared to a CFD analysis of a windsurfing fin in order to quantify the differences in performance data as well as the properties of the flow. This leads to information about the necessity of the use of FSI in comparison to regular CFD analysis and gives indication of the value of the enhanced results of the deformable analysis applied to water flow around an elastically deformable hydrofoil under different angles of attack. The performance data and flow property evaluation is done in ANSYS Fluent using the k-ω SST and k-ε model with a y+ of 1 and 35 respectively in order to be able to compare the behavior of both turbulence models. It is found that the overall lift coefficient in general is lower and that the flow is less turbulent because of softer transition due to the deformed geometry reducing drag forces. It is also found that the deformation of the tip of the hydrofoil leads to vertical lift forces. For the FSI analysis, one-way and two-way coupling were incorporated leading to the ability to compare results. It has been found that one-way coupling is sufficient as long as there is no stall present at any time.

A Joint-Industry Effort to Develop and Verify CFD Modeling Practice for Vortex-Induced Motion of a Deep-Draft Semi-Submersible

2021 ◽  
Author(s):  
Hyunchul Jang ◽  
Dae-Hyun Kim ◽  
Madhusuden Agrawal ◽  
Sebastien Loubeyre ◽  
Dongwhan Lee ◽  
...  
Keyword(s):  
Test Data ◽  
Model Test ◽  
Working Group ◽  
Cfd Modeling ◽  
Physical Model Test ◽  
Mooring Lines ◽  
Cfd Models ◽  
Induced Motion ◽  
Modeling Practice ◽  
Decay Tests

Abstract Platform Vortex Induced Motion (VIM) is an important cause of fatigue damage on risers and mooring lines connected to deep-draft semi-submersible floating platforms. The VIM design criteria have been typically obtained from towing tank model testing. Recently, computational fluid dynamics (CFD) analysis has been used to assess the VIM response and to augment the understanding of physical model test results. A joint industry effort has been conducted for developing and verifying a CFD modeling practice for the semi-submersible VIM through a working group of the Reproducible Offshore CFD JIP. The objectives of the working group are to write a CFD modeling practice document based on existing practices validated for model test data, and to verify the written practice by blind calculations with five CFD practitioners acting as verifiers. This paper presents the working group’s verification process, consisting of two stages. In the initial verification stage, the verifiers independently performed free-decay tests for 3-DOF motions (surge, sway, yaw) to check if the mechanical system in the CFD model is the same as in the benchmark test. Additionally, VIM simulations were conducted at two current headings with a reduced velocity within the lock-in range, where large sway motion responses are expected,. In the final verification stage, the verifiers performed a complete set of test cases with small revisions of their CFD models based on the results from the initial verification. The VIM responses from these blind calculations are presented, showing close agreement with the model test data.

scholarly journals Mars™ SoLoNOx Combustion System CFD Modeling

1995 ◽  
Author(s):  
Matthew E. Thomas ◽  
Mark J. Ostrander ◽  
Andy D. Leonard ◽  
Mel Noble ◽  
Colin Etheridge
Keyword(s):  
Gas Turbine ◽  
System Development ◽  
Cfd Modeling ◽  
Cfd Analysis ◽  
Combustion System ◽  
Design Environment ◽  
Turbine Engine ◽  
Combustion Modeling ◽  
Premix Combustion ◽  
Industrial Gas Turbine

CFD analysis methods were successfully implemented and verified with ongoing industrial gas turbine engine lean premix combustion system development. Selected aspects of diffusion and lean premix combustion modeling, predictions, observations and validated CFD results associated with the Solar Turbines Mars™ SoLoNOx combustor are presented. CO and NOx emission formation modeling details applicable to parametric CFD analysis in an industrial design environment are discussed. This effort culminated in identifying phenomena and methods of potentially further reducing NOx and CO emissions while improving engine operability in the Mars™ SoLoNOx combustion system. A potential explanation for the abrupt rise in CO formation observed in many gas turbine lean premix combustion systems is presented.

Thorough Verification and Validation of CFD Prediction of FPSO Wind Load for Confident Applications

2019 ◽  
Author(s):  
Wei Xu ◽  
Zhenjia (Jerry) Huang ◽  
Hyunjoe Kim
Keyword(s):  
Model Test ◽  
Cfd Simulation ◽  
Domain Size ◽  
Wind Loads ◽  
Cfd Modeling ◽  
Tunnel Floor ◽  
Mesh Resolution ◽  
Layer Effect ◽  
Modeling Practice ◽  
Prism Layer

Abstract This paper presents our verification work on CFD modeling practice for the prediction of FPSO wind loads. The modeling practice was developed from the TESK CFD JDP [1]. In the verification, the measured data from a benchmark model test were used to check CFD simulation results. The exact physical model of the model test was used in the numerical modeling (model-of-the-model). To establish high confidence in the CFD modeling and simulations, the modeling practice was thoroughly verified, which covered the following critical elements: mesh resolution, domain size, outlet boundary condition, turbulence model, Reynolds effect, wind profile, prism layer effect on total wind forces, effects of the gap between wind tunnel floor and model bottom, blockage effect due to tunnel side walls and ceiling, and effects of geometry details (small size pipes). The verification results show that CFD can be used as an alternative tool for predicting wind loads and moments on a FPSO for engineering purposes following the modeling practice, and careful QA and QC.

Hydrodynamic Coefficients of Cylinders With Strakes in Oscillatory Flows

2006 ◽  
Author(s):  
Renjeev Gopalakrishnakurup ◽  
David Clelland ◽  
Shan Huang
Keyword(s):  
Reynolds Number ◽  
Digital Signal ◽  
Water Tank ◽  
Hydrodynamic Coefficients ◽  
Oscillatory Flows ◽  
Signal Filtering ◽  
Test Matrix ◽  
Smooth Cylinder ◽  
Calm Water ◽  
Pitch Ratio

Hydrodynamic coefficients of cylinders fitted with strakes in oscillatory flows have been investigated. Three different pitch ratios have been tested, i.e. pitch ratios of infinity, 8 and 4. The cylinders are forced to oscillate in otherwise calm water in a water tank. To validate as well as to compare the experiment results, a smooth cylinder is included in the test matrix. Digital signal filtering has been found to influence the results obtained. Hence sine-fitted signals are used for obtaining the coefficients. For cylinders with strakes, it has been found that the coefficients vary little with Reynolds number. It is also concluded that the pitch ratio has a significant impact on the hydrodynamic coefficients.

Study on the Hydrodynamic Characteristics for Heave Plate Structure of Truss Spar

2010 ◽  
Author(s):  
Wenjun Shen ◽  
Yougang Tang ◽  
Liqin Liu
Keyword(s):  
Numerical Simulations ◽  
Forced Oscillation ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Hydrodynamic Coefficients ◽  
Plate Structure ◽  
Plate Spacing ◽  
Mesh Method ◽  
Truss Spar ◽  
Heave Plate

The hydrodynamic characteristics of heave plates are studied in this paper. Firstly, different motion amplitudes and plate spacing influencing hydrodynamic coefficients are considered. Secondly, heave plates with different thicknesses are calculated, the case of edges with inclined form for heave plate is also taken into account. Numerical simulations are made for the plate forced oscillation, employing the dynamic mesh method and UDF (User defined functions). The values of Cm and Cd for heave plate are calculated. It is found that, in a certain amplitude range, Cm increases with increasing of amplitudes, Cd decreases with increasing of amplitudes. The values of Cm and Cd increase with increasing of plate spacing. Furthermore with the same effective thickness, the hydrodynamic performance of heave plate with inclined form is improved greatly.

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