New Moonpool Design of Drillship for Operability Improvement

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Seon Oh Yoo ◽  
Hyun Joe Kim ◽  
Dong Yeon Lee ◽  
Booki Kim ◽  
Seung Ho Yang
Keyword(s):  
Numerical Study ◽  
Internal Flow ◽  
Navier Stokes ◽  
Flow Reduction ◽  
Wave Flume ◽  
Type Wave ◽  
Numerical Studies ◽  
Offshore Engineering ◽  
Computational Fluid Dynamics Cfd ◽  
Step Type

This study suggests three different designs of the moonpool to reduce the internal flow of the moonpool. The experimental and numerical studies were performed to improve the dillship's operability by the flow reduction in the moonpool. Based on the previous result of model tests in two-dimensional (2D) wave flume, three different moonpool designs were proposed: design-1: combination of forward recess deck, vertical bulkhead and beach-type wave absorber; design-2: a step-type forward recess deck; and design-3: a forward recess deck with beach-type wave absorber. Experimental study was carried out in the Offshore Engineering Basin for 87 K compact drillship which was 87,000 Mt as design gross tonnage. To verify the experimental results and clearly understand the internal flow of the drillship's moonpool, numerical study was carried out using Reynolds-averaged Navier–Stokes based computational fluid dynamics (CFD) code. From these studies, it was found that all the proposed designs showed significantly reduced internal flow at resonance frequency compared to the original moonpool design of the target drillship, although the characteristic of internal flow reduction was different for each moonpool design. Additional studies were carried out to obtain the improved moonpool design that is expected to further reduce the internal flow of moonpool through CFD. Based on the results of three moonpool designs, the combined one with the step-type recess deck and the wave absorber presents best performance in the viewpoint of flow reduction in the moonpool.

New Moonpool Design of Drillship for Operability Improvement

2018 ◽  
Author(s):  
Seon oh Yoo ◽  
Hyun Joe Kim ◽  
Dong Yeon Lee ◽  
Booki Kim ◽  
Seung Ho Yang
Keyword(s):  
Experimental Study ◽  
Numerical Study ◽  
Internal Flow ◽  
Flow Reduction ◽  
Wave Flume ◽  
Type Wave ◽  
Numerical Studies ◽  
Offshore Engineering ◽  
At Resonance ◽  
Step Type

This study suggests the three different designs of the moonpool to reduce the internal flow of the moonpool. The experimental and numerical studies were performed to improve the dillship’s operability by internal flow reduction of the moonpool. Based on the previous result of the moonpool only model tests in 2D wave flume, three different moonpool designs; Design-1) combination of forward recess deck, vertical bulkhead and beach-type wave absorber, Design-2) a step-type forward recess deck, and Design-3) a forward recess deck with beach-type wave absorber were selected. Experimental study was carried out in the Offshore Engineering Basin for 87K compact drillship with a moonpool. To verify the experimental results and clearly understand the internal flow of the drillship’s moonpool, numerical study was carried out using RANS based CFD. From these studies, it was found that all the proposed designs showed significantly reduced internal flow at resonance frequency compared to the 87K drillship’s moonpool, although the characteristic of internal flow reduction were different for each moonpool design. Additional studies were carried out to obtain the improved moonpool design that is expected to further reduce the internal flow of moonpool through CFD. Based on the result of three moonpool designs, a design combined with the step-type recess deck and the wave absorber was selected. As a result, the internal flow was effectively reduced in the overall wave period.

Experimental and Numerical Study on the Flow Reduction in the Moonpool of Floating Offshore Structure

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Seon Oh Yoo ◽  
Hyun Joe Kim ◽  
Dong Yeon Lee ◽  
Booki Kim ◽  
Seung Ho Yang
Keyword(s):  
Numerical Study ◽  
Internal Flow ◽  
Navier Stokes ◽  
Test Results ◽  
Internal Flows ◽  
Offshore Structure ◽  
Flow Reduction ◽  
Gap Flow ◽  
Sloshing Mode ◽  
Computational Fluid Dynamics Cfd

Recently, drillship moonpools are getting longer and wider for the higher operability. With this trend, violent internal flows are getting more concerned in terms of the safety and operability, which have been reported during the operations even in mild seas. Also, it is well known that the internal flow gives higher resistance during the transit of drillship. In this study, to see the effect of larger damping devices, a series of experimental and numerical study was carried out for the four moonpool designs; the ordinary plain moonpool, the moonpool with a recess deck, the moonpool with an isolated recess deck (island deck), and moonpool with a combination of island deck, splash plates, and wave absorber. From the model tests, it was found that the internal flow of the moonpool was significantly reduced by the application of the wave absorber. In case of the moonpool with the island deck, the sloshing mode oscillations was not observed due to the gap flow between the inner wall of the moonpool and the recess. For the in-depth understanding of the flow behaviors and characteristics, the internal flow of the moonpool has been investigated using Reynolds-averaged Navier–Stokes based computational fluid dynamics (CFD) code. The various moonpool designs were simulated to identify the effect of each device for the internal flow reduction of the moonpool. The CFD analysis results with regular waves, the water surface responses inside moonpool such as the flow pattern and resonance frequency, were compared with model test results and showed reasonably good agreements.

Experimental and Numerical Study on the Flow Reduction in the Moonpool of Floating Offshore Structure

2017 ◽  
Author(s):  
Seon Oh Yoo ◽  
Hyun Joe Kim ◽  
Dong Yeon Lee ◽  
Booki Kim ◽  
Seung Ho Yang
Keyword(s):  
Numerical Study ◽  
Internal Flow ◽  
Internal Flows ◽  
Offshore Structure ◽  
Flow Reduction ◽  
Numerical Studies ◽  
Gap Flow ◽  
Oscillation Modes ◽  
Vertical Opening ◽  
Sloshing Mode

This paper presents the efforts of experimental and numerical studies to reduce internal flow of moonpool. Drillships are equipped with a vertical opening at the center of the hull called ‘moonpool.’ Recently, the moonpools are getting longer and wider for the higher operability. With this trend, violent internal flows are getting more concerned in terms of the safety and operability, which have been reported during the operations even in mild seas. Also, it is well known that the internal flow gives higher resistance during the transit of drillship. Therefore, there have been a number of motivated researches on the reason and the source of excitation, the pattern of the internal flow and the way to suppress it. Typically an internal flow of the moonpool has two types of oscillation modes: piston- and sloshing-mode. The excited oscillations of water and resultant internal flows are highly dependent on the shape of the moonpool, partly due that the resonant periods are varied with the size and shape of the moonpool. However, since the shape and size of the drillships are quite standardized, there may be no room for the change of shape to reduce the inflow from the bottom of moonpool. Therefore, more efforts have been made to develop the damping devices such as splash plates, which can be easily installed inside of the moonpool. In this study, to see the effect of larger damping devices, a series of experimental and numerical study was carried out for the four moonpool designs; the ordinary plain moonpool, the moonpool with a recess deck, the moonpool with an isolated recess deck (island deck) and moonpool with a combination of island deck, splash plates and wave absorber. From the model tests, it was found that the internal flow of the moonpool was significantly reduced by the application of the wave absorber. In case of the moonpool with the island deck, the sloshing mode oscillations was not observed due to the gap flow between the inner wall of the moonpool and the recess, while the piston mode oscillations were remained unchanged. For the in-depth understanding of the flow behaviors and characteristics, the internal flow of the moonpool has been investigated using RANS based CFD code. The various moonpool designs were simulated to identify the effect of each device for the internal flow reduction of the moonpool. The CFD analysis results with regular waves, the water surface responses inside moonpool such as the flow pattern and resonance frequency were compared with model test results and showed reasonably good agreements.

Numerical Study of Wave Slamming on a Rectangular Slab

2012 ◽  
Vol 204-208 ◽  
pp. 4971-4977
Author(s):  
Ya Mei Lan ◽  
Wen Hua Guo ◽  
Yong Guo Li
Keyword(s):  
Numerical Study ◽  
Navier Stokes ◽  
Governing Equations ◽  
Reflected Waves ◽  
Rans Equations ◽  
Numerical Wave Flume ◽  
Wave Flume ◽  
Wave Slamming ◽  
Numerical Wave ◽  
Rectangular Slab

The CFD software FLUENT was used as the foundation to develop the numerical wave flume, in which the governing equations are the Reynolds-averaged Navier-Stokes (RANS) equations and the standard k~ε turbulence model. The wave generating and absorbing were introduced into the RANS equations as the source terms using the relaxation approach. A new module of the wave generating and absorbing function, which is suitable for FLUENT based on the volume of fluid method (VOF), was established. Within the numerical wave flume, the reflected waves from the model within the computation domain can be absorbed effectively before second reflection appears due to the wave generating boundary. The computational results of the wave pressures on the bottom of the rectangular slab were validated for the different relative clearance by the experimental data. Good agreements were found.

scholarly journals Numerical Study of the Internal Flow Field of a Centrifugal Impeller

1994 ◽  
Author(s):  
Mou-jin Zhang ◽  
Chuan-gang Gu ◽  
Yong-miao Miao
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Internal Flow ◽  
Staggered Grid ◽  
Navier Stokes ◽  
Centrifugal Impeller ◽  
High Reynolds

The complex three-dimensional flow field in a centrifugal impeller with low speed is studied in this paper. Coupled with high–Reynolds–number k–ε turbulence model, the fully three–dimensional Reynolds averaged Navier–Stokes equations are solved. The Semi–Implicit Method for Pressure–Linked Equations (SIMPLE) algorithm is used. And the non–staggered grid arrangement is also used. The computed results are compared with the available experimental data. The comparison shows good agreement.

Numerical Study of Wave Slamming on an Oscillating Flap

2014 ◽  
Author(s):  
Yanji Wei ◽  
Alan Henry ◽  
Olivier Kimmoun ◽  
Frederic Dias
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Ocean Waves ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Numerical Studies ◽  
Wave Slamming ◽  
Volume Method

Bottom hinged Oscillating Wave Surge Converters (OWSCs) are efficient devices for extracting power from ocean waves. There is limited knowledge about wave slamming on such devices. This paper deals with numerical studies of wave slamming on an oscillating flap to investigate the mechanism of slamming events. In our model, the Navier–Stokes equations are discretized using the Finite Volume method with the Volume of Fluid (VOF) approach for interface capturing. Waves are generated by a flap-type wave maker in the numerical wave tank, and the dynamic mesh method is applied to model the motion of the oscillating flap. Basic mesh and time step refinement studies are performed. The flow characteristics in a slamming event are analysed based on numerical results. Various simulations with different flap densities, water depths and wave amplitudes are performed for a better understanding of the slamming.

Pumping Speed Measurement of the Rotary Vane Vacuum Pump by Using Numerical and Experimental Approaches

2014 ◽  
Author(s):  
M. Nadeem Azam ◽  
M. Umar ◽  
M. Maqsood ◽  
Imran Akhtar ◽  
Imran Aziz
Keyword(s):  
Internal Flow ◽  
Vacuum Pump ◽  
Assessment System ◽  
Navier Stokes ◽  
Vane Pump ◽  
Navier Stokes Equation ◽  
Time Shape ◽  
Experimental Approaches ◽  
Computational Fluid Dynamics Cfd ◽  
The One

Pumping speed is the main performance parameter of a vacuum pump. In the present work, pumping speed for a three-vane rotary vacuum pump is quantified using both experimental and numerical approaches. The numerical methodology assumes continuum flow (Knudsen number < 0.1), thus allowing the use of Navier Stokes equation. Commercial computational fluid dynamics (CFD) solver i.e. Fluent, is used to discretize the governing equations. Moving / dynamic mesh technique is used for the internal flow volumes of the pump to reproduce the change-in-time shape. Complete process starting from the CAD modeling to CFD simulations is discussed in detail. The adopted approaches are generic and can be used to find the pumping speed of any other rotary vane vacuum pump. The vane pump is also tested using an assessment system, which is constructed according to DIN28432 standard. Results of experimentally measured pumping speed are in good agreement with the one computed numerically.

scholarly journals Analysis of Applicability of CFD Numerical Studies Applied to Problem When Pump Working as Turbine

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2134
Author(s):  
Frank Plua ◽  
Victor Hidalgo ◽  
P. Amparo López-Jiménez ◽  
Modesto Pérez-Sánchez
Keyword(s):  
Turbulence Models ◽  
Experimental Tests ◽  
Navier Stokes ◽  
Variable Speed ◽  
Reynolds Average Navier Stokes ◽  
Academic Literature ◽  
Numerical Studies ◽  
Speed Rotation ◽  
Computational Fluid Dynamics Cfd ◽  
Reynolds Average

The present research depicts an analysis of the implementation of computational fluid dynamics (CFD) in the study of pumps such as turbines and PATs. To highlight the benefits of CFDs for PAT studies, results from both experimental tests have been compared to better understand the reproduction error phenomena. For this, data analysis used in successful models has been applied to determine variables and parameters, and to report a low relative error. The results show that most of the studies focused on fixed speed rotation with some cases of variable speed rotation. Furthermore, there is not enough information in the academic literature for PAT of axial and mixed flows with fixed and variable speed. Finally, turbulence models based on Reynolds average Navier–Stokes (RANS) have been used to simulate PATs with fixed speed rotation in most cases.

Experimental and Numerical Study for Drillship Moonpool Gap Resonances in Stationary and Transit Conditions in Wave Flume

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
Aichun Feng ◽  
Allan Magee ◽  
W. G. Price
Keyword(s):  
Numerical Study ◽  
Numerical Data ◽  
Resonance Phenomenon ◽  
Wave Direction ◽  
Wave Flume ◽  
Numerical Studies ◽  
Wave Elevation ◽  
Gap Resonance ◽  
Sloshing Mode ◽  
Transit Speed

Abstract Experimental and numerical studies are performed to investigate drillship moonpool gap resonance in both stationary and transit conditions in a wave flume. This study contains an assessment of the influence of size and depth of the moonpool on the gap resonance phenomenon. An openfoam-based computational fluid dynamics (CFD) model was established, and the numerical data show good agreement with measurements from the model tests. Both piston and sloshing mode gap resonances are clearly observed. This study shows that the gap resonance frequency and wave elevation response amplitude operator (RAO) inside the moonpool are dependent on its dimensions, and the transit speed of the drillship and wave direction significantly influences the characteristics of gap resonances. It is noticed that the nearness of the wave flume sidewalls significantly influences the piston and sloshing wave elevation RAO at certain frequencies regardless of moonpool length and draft.

Numerical Prediction of Bare and Straked Cylinder VIV

2006 ◽  
Author(s):  
Yiannis Constantinides ◽  
Owen H. Oakley
Keyword(s):  
Turbulence Models ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Numerical Studies ◽  
Vortex Induced Vibrations ◽  
Computational Fluid Dynamics Cfd ◽  
Offshore Industry ◽  
High Reynolds ◽  
Cfd Method

The prediction of deepwater riser Vortex Induced Vibrations (VIV) is one of the most challenging areas in the offshore industry. Numerous experimental and numerical studies have been performed in an effort to improve the understanding and prediction of cylinder VIV behavior. This paper presents the numerical simulation of rigid circular sections, both bare and fitted with strakes, using a second order accurate finite element computational fluid dynamics (CFD) method. Two turbulence models are examined: the Spalart-Allmaras Reynolds Averaged Navier Stokes (RANS) and the Detached Eddy Simulation (DES). Pragmatic high Reynolds number simulations of fixed and moving cylinders are presented and compared with laboratory experiments. Flow visualization provides insights on how strakes mitigate VIV. Comparisons between RANS and DES results are also presented and discussed.

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