Techno Press
Tp_Editing System.E (TES.E)
Login Search
You logged in as

ose
 
CONTENTS
Volume 12, Number 2, June 2022
 


Abstract
In this study, the nominal wake field of a semi-displacement type high-speed vessel was computed at full scale by using CFD (Computational Fluid Dynamics) and GEOSIM-based approaches. A scale effect investigation on nominal wake field of benchmark Athena vessel was performed with two models which have different model lengths. The members of the model family have the same Fr number but different Re numbers. The spatial components of nominal wake field have been analyzed by considering the axial, radial and tangential velocities for models at different scales. A linear feature has been found for radial and tangential components while a nonlinear change has been obtained for axial velocity. Taylor wake fraction formulation was also computed by using the axial wake velocities and an extrapolation technique was carried out to get the nonlinear fit of nominal wake fraction. This provides not only to observe the change of nominal wake fraction versus scale ratios but also to estimate accurately the wake fraction at full-scale. Extrapolated full-scale nominal wake fractions by GEOSIM-based approach were compared with the full-scale CFD result, and a very good agreement was achieved. It can be noted that the GEOSIM-based extrapolation method can be applied for estimation of the nominal wake fraction of semi-displacement type high-speed vessels.

Key Words
full-scale athena hull; GEOSIM series; nominal wake fraction; scale effect

Address
Ugur Can: Department of Naval Architecture and Marine Engineering, Yildiz Technical University, Istanbul, Turkey
Sakir Bal: Department of Naval Architecture and Marine Engineering, Istanbul Technical University, Istanbul, Turkey

Abstract
To ensure stable performance, adaptive regulators with new theories are designed for steel-covered offshore platforms to withstand anomalous wave loads. This model shows how to control the vibration of the ocean panel as a solution using new results from Lyapunov's stability criteria, an evolutionary bat algorithm that simplifies computational complexity and utilities. Used to reduce the storage space required for the method. The results show that the proposed operator can effectively compensate for random delays. The results show that the proposed controller can effectively compensate for delays and random anomalies. The improved prediction method means that the vibration of the offshore structure can be significantly reduced. While maintaining the required controllability within the ideal narrow range.

Key Words
evolved control systems; offshore platforms; predictive control; time delays

Address
C.C. Hung: Department of Mechanical Engineering, National Taiwan University, Taiwan;
Faculty of National Hsin Hua Senior High School, Tainan, Taiwan
T. Nguyen: Ha Tinh University, Dai Nai Campus, No. 447, Street 26/3, Dai Nai Ward, Ha Tinh City, Vietnam


Abstract
oil and gas industry, FPSO concept is the most popular hull form and ship shaped hull form dominants the FPSO market. Only a non-ship-shaped hull in operations with minor market shares is the cylindrical FPSO hull with medium to small storage capability. To add contracting options and competitions to reduce field development costs, an innovative turretless low motion hull, eco-FPSO, with 1MM bbls oil storage capacity and suitable for installing topsides modulars and equipping with regular SCRs, was first introduced in Zou (2020a). Dynamic characteristic responses of the eco-FPSO compared to the traditional SS-FPSO hull and DD-Semi platform are presented and discussed in this paper, suitability and feasibility of the proposed hull have been demonstrated and validated through extensive analyses in 10-yrp, 100-yrp and 1,000-yrp hurricanes in ultra-deepwater central GoM.

Key Words
harsh environmental conditions; low motion; minimum airgap; motion RAOs; porch vertical displacement; regular SCRs; ship shaped FPSO; turretless; porch vertical velocity and acceleration RAOs; wave upwelling RAOs

Address
Jun Zou: Kent Houston Offshore Engineering PLC, 200 Westlake Park Blvd, Suite 1100, Houston, TX 77079, USA

Abstract
More and more shipping containers are falling into the sea due to bad weather. Containers lost at sea negatively affect the shipping line, the trader and the consumer, and the environment. The question of locating and recovering dropped containers is a challenging engineering problem. Model-testing of small-scaled container models is proposed as an efficient way to investigate their falling trajectories to salvage them. In this study, we first build a standard 20-ft container model in SOLIDWORKS. Then, a three-dimensional (3D) geometric model in the STL (Standard Tessellation Language) format is exported to a Stratasys F170 Fused Deposition Modeling (FDM) printer. In total, six models were made of acrylonitrile styrene acrylate (ASA) and printed for the purpose of testing. They represent three different loading conditions with different densities and center of gravity (COG). Two samples for each condition were tested. The physical models were dropped into the towing tank of University of New Orleans (UNO). From the experimental tests, it is found that the impact of the initial position after sinking can cause a certain initial rolling velocity, which may have a great impact on the lateral displacement, and subsequently affect the final landing position. This series of model tests not only provide experimental data for the study of the trajectory of box-shape objects but also provide a valuable reference for maritime salvage operations and for the pipeline layout design.

Key Words
3D printing; container model; Fused Deposition Modeling (FDM); maritime industry; trajectory

Address
Yi Li, Ryan Thiel, George Morrissey and Xiaochuan Yu: Boysie Bollinger School of Naval Architecture and Marine Engineering, University of New Orleans, USA
Hanqi Yu: Department of Mathematics, University of New Orleans, USA
Damon Smith: Department of Mechanical Engineering, University of New Orleans, USA
M.M. Khonsari: Department of Mechanical & Industrial Engineering, Louisiana State University, USA

Abstract
In the present study, we focus on the CFD simulations for the performance and the rotor-generated wake of a model-scale wind turbine which was designed for wave tank experiments. The CFD simulations with fully resolved rotor geometry are performed using MARIN's community-based open-source CFD code ReFRESCO. The absolute formulation method (AFM) is leveraged to model the rotating wind turbine. The k-w SST turbulence model is adopted in the incompressible Reynolds Averaged Navier-Stokes (RANS) simulations. First, the thrust and torque coefficients, CT and CP are calculated at different Tip Speed Ratios (TSR), and the results are compared against the experimental data and previous numerical results. The pressure distribution of the turbine blades at the 70% span is obtained and compared to the results obtained by other tools. Then, a verification study aiming at quantifying the discretization uncertainty of the turbine performance with respect to the grid resolution in the wake region is performed. Last, the rotor-generated wake at the TSR of 7 is presented and discussed.

Key Words
CFD simulation; FOWT; numerical uncertainties; wind turbine

Address
Maokun Ye: Department of Ocean Engineering, Texas A&M University, College Station, Texas, USA
Hamn-Ching Chen :Department of Ocean Engineering, Texas A&M University, College Station, Texas, USA;
Zachry Department of Civil & Environmental Engineering,
Texas A&M University, College Station, Texas, USA
Arjen Koop: MARIN – Maritime Research Institute Netherlands, Wageningen, The Netherlands



Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2022 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-2-736-6800 (SCS, EAS, WAS, ANR) +82-42-828-7995 (GAE, SEM, SSS, CAC) Fax : +82-2-736-6801, Email: info@techno-press.com