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.

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.

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.

scholarly journals Numerical Study on Wave-Ice Interaction in the Marginal Ice Zone

2020 ◽  
Vol 9 (1) ◽  
pp. 4
Author(s):  
Tiecheng Wu ◽  
Wanzhen Luo ◽  
Dapeng Jiang ◽  
Rui Deng ◽  
Shuo Huang
Keyword(s):  
Sea Ice ◽  
Numerical Study ◽  
Test Results ◽  
Towing Tank ◽  
Marginal Ice Zone ◽  
Computational Fluid Dynamics Cfd ◽  
Numerical Research ◽  
Ice Floes ◽  
Cfd Method ◽  
Six Degree Of Freedom

The effect of waves on ice sheet is critical in the marginal ice zone (MIZ). Waves break large sea ice into small pieces and cause them to collide with each other. Simultaneously, the interaction between sea ice and waves attenuates these waves. In this study, a numerical research is conducted based on a computational fluid dynamics (CFD) method to investigate the response of single ice floe to wave action. The obtained results demonstrate that the sea ice has a violent six degree of freedom (6DoF) motion in waves. Ice floes with different sizes, thicknesses, and shapes exhibit different 6DoF motions under the action of waves. The heave and surge response amplitude operator (RAO) of the sea ice are related to wavelength. Furthermore, the overwash phenomenon can be observed in the simulation. The obtained results are compared with the model test in the towing tank based on artificial ice, and they agree well with test results.

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.

Aero Engine Axi-Symmetric Convergent-Constant Area Intake 3D Simulation Using a Panel Method Approach

2005 ◽  
Author(s):  
Ioannis Templalexis ◽  
Pericles Pilidis ◽  
Geoffrey Guindeuil ◽  
Petros Kotsiopoulos ◽  
Vassilios Pachidis
Keyword(s):  
Three Dimensional ◽  
Internal Flow ◽  
Navier Stokes ◽  
Lattice Method ◽  
Simulation Code ◽  
Lower Lip ◽  
Vortex Lattice Method ◽  
Constant Area ◽  
Computational Fluid Dynamics Cfd ◽  
General Effort

This study has been carried out as a part of a general effort to develope a powerful simulation code, based on the Vortex Lattice Method (VLM), capable of simulating adequately accurate and comparatively fast, internal flow regimes. It utilizes a convergent – (nearly) constant area axi-symmetric intake three dimensional geometry, emerged as a surface of revolution from the CFM56-5B2 lower lip geometry. The study focuses on the three most critical planes, which are the inlet of the intake, the outlet of the diverging section and the outlet of the intake. Moreover, the sensitivity of the simulation on the variation of the Angle Of Attack (AOA) is tested for four different settings equally spaced, ranging from 0 to 20 degrees. The comparison is carried out on both two-dimensional velocity distributions and average values. The VLM simulation code was based on an existing code, which was modified in order to be adapted to the Reynolds Average Navier-Stokes (RANS) Computational Fluid Dynamics (CFD) boundary conditions.

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.

scholarly journals ALTERNATIVE STUDY OF A BEVEL PUNCH-ASSISTED ECAE SCHEME

2018 ◽  
Vol 24 (4) ◽  
pp. 306 ◽  
Author(s):  
Alexander V. Perig ◽  
Nikolai N. Golodenko
Keyword(s):  
Stokes Equations ◽  
Equal Channel Angular Extrusion ◽  
Numerical Study ◽  
Navier Stokes ◽  
Cylindrical Shape ◽  
Navier Stokes Equations ◽  
Velocity Gradients ◽  
Inclination Angles ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Velocities

<p>It is a common practice in pressure forming to make an Equal Channel Angular Extrusion (ECAE) of a workpiece through a die with channel intersection angle 2θ = 90° using a standard punch of brick or cylindrical shape with 2θ<sub>0</sub> = 90°. However Nejadseyfi et al (2015) have applied a beveled 2θ<sub>0</sub>-punch to the process of ECAE through a standard angular die of Segal geometry with 2θ = 90° and 2θ<sub>0</sub> ≠ 2θ. The scope of the article is focused on an alternative numerical study of Nejadseyfi-ECAE-Scheme using techniques of Computational Fluid Dynamics (CFD). A finite-difference method was applied to the numerical solution of the boundary value problem for the Navier-Stokes equations in the form of a vorticity transfer equation. The complex of 2D plots for CFD-derived fields of flow lines and flow velocities and 3D plots for spatial distributions of flow velocities and tangential stresses were firstly derived for Nejadseyfi-ECAE-Scheme during viscous flow of polymer workpiece models through angular die with 2θ = 90° for the different punch inclination angles 30° ≤ 2θ<sub>0</sub> ≤ 150°. It was found that Nejadseyfi-ECAE-Scheme provides enhancement of the rotary modes of intensive deformations during ECAE. Results provide visualization of velocity gradients and macroscopic rotation and the illustration of Nejadseyfi et al’s ideas from an alternative CFD-based viewpoint.</p>

scholarly journals A Numerical Study of Spray Strips Analysis on Fridsma Hull Form

Fluids ◽  
2021 ◽  
Vol 6 (11) ◽  
pp. 420
Author(s):  
Samuel ◽  
Andi Trimulyono ◽  
Parlindungan Manik ◽  
Deddy Chrismianto
Keyword(s):  
Fluid Dynamics ◽  
Numerical Study ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Total Resistance ◽  
Navier Stokes Equation ◽  
Computational Fluid Dynamics Cfd ◽  
Wetted Surface Area ◽  
Volume Method ◽  
Dynamics Problems

Spray strips are deflectors added to the hull to reduce the Wetted Surface Area (WSA). The reduced WSA will decrease the total ship drag caused by the deflection of the spray strip installation. The research aimed to predict the function of the spray strip to improve ship performance using Computational Fluid Dynamics (CFD). The numerical approach in this study used the Finite Volume Method (FVM) with the RANS (Reynolds-averaged Navier–Stokes) equation to solve fluid dynamics problems. VOF (Volume of Fluid) was used to model the water and air phases. The results of this study indicated that the number of spray strips would have a significant effect compared to without using a spray strip. Spray strips with three strips could reduce the total resistance by 4.9% at Fr 1.78. Spray strips would increase the total resistance value by 2.1% at low speeds. Spray strips were effective for reducing total resistance at Fr > 1 or the planing mode conditions. The total resistance prediction used three suggestion profiles with the best performance to reduce total resistance by 6.0% at Fr 1.78.

Research on the Numerical Simulation of Internal Flow Field and Energy Efficiency of Ventilator

2015 ◽  
Vol 713-715 ◽  
pp. 602-605
Author(s):  
Zhu Jue Tong ◽  
Xiao Ling Wang ◽  
Kai Zhang ◽  
Shu Xing Wu
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Energy Efficiency ◽  
Flow Field ◽  
Three Dimensional ◽  
Internal Flow ◽  
Secondary Flows ◽  
Local Flow ◽  
Gap Flow ◽  
Computational Fluid Dynamics Cfd

In the present study, the effects of ventilator geometries on the its performance were numerically simulated using the computational fluid dynamics (CFD) program. For a certain type ventilator, three-dimensional inner flow field was derived firstly, such as local flow field at the meridional and rotary plane of ventilator, the gap flow between the impeller and air outlet, and the secondary flows in impeller channel were studied in detail, and some suggestions are given to improve the profile of velocity. The above results would be helpful to the optimization and modification of ventilator.

Sign in / Sign up

Export Citation Format

Share Document