Effects on Drillship Resistance of a Large Moonpool Using CFD Simulations With Experimental Validation

2016 ◽  
Author(s):  
Lucas do Vale Machado ◽  
Antonio Carlos Fernandes ◽  
Anis Altaf Hussain
Keyword(s):  
Oil And Gas ◽  
Numerical Study ◽  
Experimental Tests ◽  
Numerical Approach ◽  
Process Efficiency ◽  
Floating Structure ◽  
Cfd Models ◽  
Waves And Currents ◽  
Mesh Density ◽  
In Transit

Drillship is a marine vessel designed for drilling purposes of oil and gas wells. This kind of vessel has what is called a moonpool that is an opening on the base of the hull used for drilling operation. Nowadays, in search of better process efficiency, some of these drillships are being constructed with dual-derrick and are in need of a larger moonpool, which results in some effects on the floating structure, such as resistance increase. The main objective of this paper is to investigate the influence of shape and size of the moonpool on the resistance of a drillship dual derrick, while in transit. It presents the application of a commercial CFD (Computational Fluid Dynamics) software as a numerical approach to calculate the flow around a drillship without neglecting free surface effects. Throughout this work, the made assumptions, applied boundary conditions and appropriate mesh density studies are thoroughly discussed. Verification assessment is part of the work. In addition to the numerical study, some experimental tests were done at LOC/UFRJ (Laboratório de Ondas e Correntes – Laboratory of Waves and Currents) to validate the numerical approach. The comparison between simulation results and experiments allows the analysis of the present CFD models benefits and limitations, providing guidelines for similar future studies. The overall match between laboratory and virtual tests results supports the expansion of this procedure to other vessels and offshore floating units. The results of this work clarify the motion inside the moonpool and its effects. Furthermore, it gives the results of several different moonpool profiles that were optimized for this specific hull.

CFD Virtual Testing for Resistance, Wind and Current Loads on a Supply Boat

2012 ◽  
Author(s):  
Daniel Fonseca de Carvalho e Silva
Keyword(s):  
Numerical Approach ◽  
Interfacial Effects ◽  
Environmental Loads ◽  
Towing Tank ◽  
Cfd Models ◽  
Fluid Resistance ◽  
Ansys Cfx ◽  
Mesh Density ◽  
Simulation Results ◽  
Icem Cfd

Ship and platforms environmental loads are often predicted by model scale experiments or empirical calculations only. This paper presents the application of a commercial CFD (Computational Fluid Dynamics) software as a numerical approach to calculate the flow around a supply boat considering current, wind loads and fluid resistance determination. Since, owing to many practical situations, free surface effects can be neglected, the above and underwater problems can be uncoupled and independently evaluated, although for higher Froude number cases in the resistance determination the interfacial effects have to be considered. Throughout this paper, the assumptions adopted and the boundary conditions applied are discussed. All meshes were developed on ICEM CFD® and appropriate mesh density studies indicate that meshes with approximately 2 million nodes can represent the experiments accurately. The simulations were conducted using the ANSYS CFX® solver, using Perl scripting for automatic evaluation of multiple run settings and simulation execution at Petrobras Research Center Clusters. The results for each case are compared with either towing tank or wind tunnel experimental data, both harvested at IPT (Instituto de Pesquisas Tecnológicas). The comparison between simulation results and experiments allows the analysis of the present CFD models benefits and limitations, providing guidelines for future similar studies. The overall match between laboratory and virtual tests results supports the expansion of this procedure to other vessels and offshore floating units.

A Combined Experimental and Numerical Study of Flow Past a Single Step Cylinder

2010 ◽  
Author(s):  
Chris R. Morton ◽  
Serhiy Yarusevych
Keyword(s):  
Vortex Shedding ◽  
Numerical Study ◽  
Experimental Tests ◽  
Numerical Approach ◽  
Single Step ◽  
Wake Flow ◽  
Cylinder Wake ◽  
Flow Topology ◽  
Single Vortex ◽  
Flow Past

The current study investigates flow past a step cylinder for ReD = 1050 and D/d = 2 using both experimental and numerical methods. The focus of the study is on the vortex shedding and vortex interactions occurring in the step cylinder wake. Flow visualization with hydrogen bubble technique and planar Laser Induced Fluorescence has shown that three distinct spanwise vortex cells form: a single vortex shedding cell in the wake of the small cylinder and two vortex shedding cells in the wake of the large cylinder. Vortex connections form between the spanwise vortices in these cells downstream of the step, and vortex dislocations occur at cell boundaries. Complementary to the experimental tests, an LES-RANS hybrid numerical simulation is used to model the flow development. A comparison of the experimental and numerical results indicates that the numerical approach adequately models vortex dynamics in the wake of a step cylinder and, thus, may be used to analyze time dependent, three-dimensional flow topology which is difficult to characterize quantitatively using experimental methods.

Numerical Study of Modular 5.56 mm Standard Assault Rifle Referring to Dynamic Characteristics

2015 ◽  
Vol 65 (6) ◽  
pp. 431 ◽  
Author(s):  
P. Płatek ◽  
K. Damaziak ◽  
J. Małachowski ◽  
P. Kupidura ◽  
R. Woźniak ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Multibody System ◽  
Numerical Study ◽  
Experimental Tests ◽  
Numerical Approach ◽  
Complex Character ◽  
Strength Parameters ◽  
Numerical Studies ◽  
Modelling Methodology ◽  
Good Agreement

<p>The paper describes investigations carried out to verify a loading mechanism of a newly designed modular assault rifle MSBS-5.56. A complex character of interaction between its elements during a reloading process encouraged the authors implement a numerical approach based on the multibody system to specify the essential dynamic characteristics. The achieved results were compared to the data recorded during the experimental tests on the shooting range. Owing to the proposed modelling methodology, a good agreement between experimental and numerical studies has been achieved.<br />A numerical model presented in the paper will be applied in further investigations to analyse strength parameters of the reloading mechanism and to conduct additional optimisation studies.</p>

PARALLEL SOLVER FOR THE SIMULATIONS OF DETONATION WAVES ON UNSTRUCTURED GRIDS

2020 ◽  
Author(s):  
A. I. Lopato ◽  
◽  
A. G. Eremenko ◽  
Keyword(s):  
Chemical Kinetics ◽  
Numerical Scheme ◽  
Unstructured Grids ◽  
Numerical Study ◽  
Numerical Approach ◽  
Detonation Waves ◽  
Detailed Chemical Kinetics ◽  
Parallel Solver ◽  
Further Development ◽  
Detailed Chemical

Recently, we developed a numerical approach for the simulation of detonation waves on fully unstructured grids and applied it to the numerical study of the mechanisms of detonation initiation in multifocusing systems. Current work is devoted to further development of our numerical approach, namely, parallelization of the numerical scheme and introduction of more comprehensive detailed chemical kinetics scheme.

Experimental Studies Concerning the Semipermeable Membrane Separation Efficiency for 134Cs, 137Cs, 57Co, 58Co, 60Co, 54Mn in Liquid Radioactive Waste I. Treatment of secondary waste from POD decontamination procedure

2008 ◽  
Vol 59 (5) ◽  
Author(s):  
Mirela Dulama ◽  
Nicoleta Deneanu ◽  
Cristian Dulama ◽  
Margarit Pavelescu
Keyword(s):  
Membrane Separation ◽  
Separation Efficiency ◽  
Liquid Radioactive Waste ◽  
Experimental Studies ◽  
Experimental Tests ◽  
Suspended Solid ◽  
Process Efficiency ◽  
Active Charcoal ◽  
Precipitation Process ◽  
Pre Treatment

The paper presents the experimental tests concerning the treatment by membrane techniques of radioactive aqueous waste. Solutions, which have been treated by using the bench-scale installation, were radioactive simulated secondary wastes from the decontamination process with modified POD. Generally, an increasing of the retention is observed for most of the contaminants in the reverse osmosis experiments with pre-treatment steps. The main reason for taking a chemical treatment approach was to selectively remove soluble contaminants from the waste. In the optimization part of the precipitation step, several precipitation processes were compared. Based on this comparison, mixed [Fe(CN)6]4-/Al3+/Fe2+ was selected as a precipitation process applicable for precipitation of radionuclides and flocculation of suspended solid. Increased efficiencies for cesium radionuclides removal were obtained in natural zeolite adsorption pre-treatment stages and this was due to the fact that volcanic tuff used has a special affinity for this element. Usually, the addition of powdered active charcoal serves as an advanced purifying method used to remove organic compounds and residual radionuclides; thus by analyzing the experimental data (for POD wastes) one can observe a decreasing of about 50% for cobalt isotopes subsequently to the active charcoal adsorption.. The semipermeable membranes were used, which were prepared by the researchers from the Research Center for Macromolecular Materials and Membranes, Bucharest. The process efficiency was monitored by gamma spectrometry.

Tank Test and Numerical Simulation of Spar Type Floating OTEC

2021 ◽  
Author(s):  
Shunka C. Hirao ◽  
Jun Umeda ◽  
Kentaroh Kokubun ◽  
Toshifumi Fujiwara
Keyword(s):  
Numerical Simulations ◽  
Cold Water ◽  
Scaling Law ◽  
Internal Flow ◽  
Bending Moment ◽  
Floating Structure ◽  
Waves And Currents ◽  
Tank Test ◽  
Safety Assessments ◽  
Ocean Thermal Energy

Abstract National Maritime Research Institute, NMRI, had been studying the analytical method on safety assessments of floating power generation facilities for ten years more. As a part of these studies, an Ocean Thermal Energy Conversion (OTEC) was also studied in our institute. The OTEC normally has a very long and thick Cold-Water Pipe (CWP) with an unanchored end to pump up a large amount of cold-water continuously. From the viewpoints of the safety assessments of the OTEC operation, it is noteworthy to confirm the effect of the existing long pipe against a floating unit/body and an effect of internal flowing water. It is necessary, moreover, to consider the Vortex Induced Vibration (VIV) effect for floater motions and structural analysis of the pipe itself and a connecting point of the floating structure. In this paper, the results of model tests and numerical simulations of a spar type floating OTEC with a single CWP in waves and currents are presented. The CWP model was made of material fitting the scaling law for a planned full scale OTEC. The specific and unique phenomena of the floating OTEC were confirmed from the model test results. Based on the results of the tank tests and the numerical simulations, we confirmed the necessary items and arrangements for safety evaluations. In detail, the internal flow increased the bending moment at the connection point.

Thermal jet drilling of granite rock: a numerical 3D finite-element study

2021 ◽  
Vol 379 (2196) ◽  
pp. 20200128
Author(s):  
Timo Saksala ◽  
Reijo Kouhia ◽  
Ahmad Mardoukhi ◽  
Mikko Hokka
Keyword(s):  
Finite Elements ◽  
Numerical Study ◽  
Thermal Flux ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Mass Scaling ◽  
Granite Rock ◽  
Fracture Dynamics ◽  
Rock Heterogeneity ◽  
Thermal Drilling

This paper presents a numerical study on thermal jet drilling of granite rock that is based on a thermal spallation phenomenon. For this end, a numerical method based on finite elements and a damage–viscoplasticity model are developed for solving the underlying coupled thermo-mechanical problem. An explicit time-stepping scheme is applied in solving the global problem, which in the present case is amenable to extreme mass scaling. Rock heterogeneity is accounted for as random clusters of finite elements representing rock constituent minerals. The numerical approach is validated based on experiments on thermal shock weakening effect of granite in a dynamic Brazilian disc test. The validated model is applied in three-dimensional simulations of thermal jet drilling with a short duration (0.2 s) and high intensity (approx. 3 MW m −2 ) thermal flux. The present numerical approach predicts the spalling as highly (tensile) damaged rock. Finally, it was shown that thermal drilling exploiting heating-forced cooling cycles is a viable method when drilling in hot rock mass. This article is part of the theme issue ‘Fracture dynamics of solid materials: from particles to the globe’.

Numerical Investigation of Ductile Fracture in Pipelines Under Complex Loading Using a Phenomenological Damage Model

2021 ◽  
Author(s):  
Iago S. Santos ◽  
Diego F. B. Sarzosa
Keyword(s):  
Ductile Fracture ◽  
Mechanical Response ◽  
Numerical Study ◽  
Damage Model ◽  
Stress Triaxiality ◽  
Numerical Procedure ◽  
Complex Loading ◽  
Experimental Tests ◽  
Compact Tension ◽  
Axial Tensile

Abstract This paper presents a numerical study on pipes ductile fracture mechanical response using a phenomenological computational damage model. The damage is controlled by an initiation criterion dependent on the stress triaxiality and the Lode angle parameter, and a post-initiation damage law to eliminate each finite element from the mesh. Experimental tests were carried out to calibrate the elastoplastic response, damage parameters and validate the FEM models. The tested geometries were round bars having smooth and notched cross-section, flat notched specimens under axial tensile loads, and fracture toughness tests in deeply cracked bending specimens SE(B) and compact tension samples C(T). The calibrated numerical procedure was applied to execute a parametric study in pipes with circumferential surface cracks subjected to tensile and internal pressure loads simultaneously. The effects of the variation of geometric parameters and the load applications on the pipes strain capacity were investigated. The influence of longitudinal misalignment between adjacent pipes was also investigated.

In-plane response of unreinforced masonry walls confined by reinforced concrete tie-columns and tie-beams

2017 ◽  
Vol 20 (11) ◽  
pp. 1632-1643 ◽  
Author(s):  
Masoud Amouzadeh Tabrizi ◽  
Masoud Soltani
Keyword(s):  
Numerical Study ◽  
Nonlinear Behavior ◽  
Numerical Approach ◽  
Masonry Wall ◽  
Masonry Walls ◽  
Lateral Loads ◽  
Confined Masonry ◽  
Smeared Crack ◽  
Modeling Strategy ◽  
Reversed Cyclic

This article focuses on the experimental and analytical investigations of masonry walls surrounded by tie-elements under in-plane loads. The experimental results of an unconfined and a confined masonry wall, tested under reversed cyclic lateral loads, are presented. For numerical study, a micro-modeling strategy, using smeared-crack-based approach, is adopted. In order to validate the numerical approach, experimental test results and data obtained from the literature are used, and through a systematic parametric study, the influence of adjoining walls and number of tie-columns on the seismic behavior of confined masonry panels is numerically assessed and a simple but rational method for predicting the nonlinear behavior of these structures is proposed.

scholarly journals Numerical Study on the Heading Misalignment and Current Velocity Reduction of a Vessel-Shaped Offshore Fish Farm

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Lin Li ◽  
Zhiyu Jiang ◽  
Jungao Wang ◽  
Muk Chen Ong
Keyword(s):  
Numerical Study ◽  
Single Point ◽  
Fish Farm ◽  
Misalignment Angle ◽  
Fish Welfare ◽  
Integrated Method ◽  
Waves And Currents ◽  
Spread Area ◽  
Fish Cages ◽  
Current Reduction

Recently, the concept of a vessel-shaped fish farm was proposed for open sea applications. The fish farm comprises a vessel-shaped floater, five fish cages, and a single-point mooring system. Such a system weathervanes, and this feature increases the spread area of fish waste. Still, the downstream cages may experience decreased exchange of water flow when the vessel heading is aligned with the current direction, and fish welfare may be jeopardized. To ameliorate the flow conditions, a dynamic positioning (DP) system may be required, and its power consumption should relate to the heading misalignment. This paper proposes an integrated method for predicting the heading misalignment between the vessel-shaped fish farm and the currents under combined waves and currents. A numerical model is first established for the fish farm system with flexible nets. Current reduction factors are included to address the reduction in flow velocity between net panels. The vessel heading is obtained by finding the equilibrium condition of the whole system under each combined wave and current condition. Then, the Kriging metamodel is applied to capture the relation between the misalignment angle and environmental variables, and the probability distribution of this misalignment angle is estimated for a reference site. Finally, the requirement for the DP system to improve the flow condition in the fish cages is discussed.

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