A site-specific CFD study of passing ship effects on multiple moored ships

Chen, Hamn-Ching,Chen, Chia-Rong,Huang, Erick T. Techno-Press 2019 Ocean systems engineering Vol.9 No.1

A local-analytic-based Navier-Stokes solver has been employed in conjunction with a compound ocean structure motion analysis program for time-domain simulation of passing ship effects induced by multiple post-Panamax class ships in the exact condition of a real waterway. The exact seabed bathymetry was reproduced to the utmost precision attainable using the NOAA geophysical database for Virginia Beach, NOAA nautical charts for Hampton Roads and Norfolk harbor, and echo sounding data for the navigation channel and waterfront facilities. A parametric study consists of 112 simulation cases with various combinations of ship lanes, ship speeds, ship heading (inbound or outbound), channel depths, drift angles, and passing ship coupling (in head-on or overtaking encounters) were carried out for two waterfront facilities at NAVSTA Norfolk and Craney Island Fuel Terminal. The present paper provides detailed parametric study results at both locations to investigate the site-specific passing ship effects on the motion responses of ships moored at nearby piers.

복합 전시판매공간 개념의 ‘D’사 공간 계획안

함현진(Hamn, Hyun-Jin),김문덕(Kim, Moon-Duck) 한국실내디자인학회 2009 한국실내디자인학회 학술대회논문집 Vol.11 No.1

The spending pattern of modern day consumers are increasingly involved in information and new cultures due to both technological and industrial advancement and higher standards of living. In addition, the commercial space itself like retail stores, office interior spaces are becoming more important in terms of marketing and tools to deliver goods and services to consumers more effectively. However, most interior spaces are not fully serving the needs of their consumers partially due to outdated creativity and poor management. Therefore, Research and Development Center (R&D) is planned to assist in maximizing the use of interior design space that can deliver best experiences and information of products and services to consumers. In addition, R&D center will help maximizing corporate profit in the coming years.

CFD simulation of compressible two-phase sloshing flow in a LNG tank

Chen, Hamn-Ching Techno-Press 2011 Ocean systems engineering Vol.1 No.1

Impact pressure due to sloshing is of great concern for the ship owners, designers and builders of the LNG carriers regarding the safety of LNG containment system and hull structure. Sloshing of LNG in partially filled tank has been an active area of research with numerous experimental and numerical investigations over the past decade. In order to accurately predict the sloshing impact load, a new numerical method was developed for accurate resolution of violent sloshing flow inside a three-dimensional LNG tank including wave breaking, jet formation, gas entrapping and liquid-gas interaction. The sloshing flow inside a membrane-type LNG tank is simulated numerically using the Finite-Analytic Navier-Stokes (FANS) method. The governing equations for two-phase air and water flows are formulated in curvilinear coordinate system and discretized using the finite-analytic method on a non-staggered grid. Simulations were performed for LNG tank in transverse and longitudinal motions including horizontal, vertical, and rotational motions. The predicted impact pressures were compared with the corresponding experimental data. The validation results clearly illustrate the capability of the present two-phase FANS method for accurate prediction of impact pressure in sloshing LNG tank including violent free surface motion, three-dimensional instability and air trapping effects.

Ricketts분석에 의한 청소년기 정상교합자에 대한 두부방사선 계측학적 연구

함수만,손병화 대한치과교정학회 1985 대한치과교정학회지 Vol.15 No.2

This study was performed to establish the cephalometric standards and growth change of Korean teen-age group by Ricketts analysis. A roentgenocephalometric study was from 365 subjects, that consist of 159 males, 206 females with normal occlusion, acceptable profile and no history of orthodontic and prosthodontic treatment. The results were as follows: 1. The tables of means, standard deviation from measured values were made, (male, female, both sex). 2. The tables of regression equations from measured values were made to establish the relation-ship between age and each item. (male, female, both sex). 3. All linear measurements of each item in male were greater than in females. 4. Items which show more linear than any other items were condyle axis, facial axis length, corpus length and upper molar position.

CFD study of an iterative focused wave generation method

Haoyuan Gu,Hamn-Ching Chen Techno-Press 2023 Ocean systems engineering Vol.13 No.1

An iterative focused wave generation method is developed and implemented in a local analytic based Navier-Stokes solver. This wave generation method is designed to reproduce the target focused wave by matching the target amplitude spectrum and phase angle. A 4-waves decomposition scheme is utilized to obtain the linearised component of the output wave. A model test studying the interaction between different focused waves and a fixed cylinder is selected as the target for the wave generation approach. The numerical wave elevations and dynamic pressure on the cylinder are compared with the experimental measurement and other state-of-the-art numerical methods' results. The overall results prove that the iterative adjustment method is able to optimize the focused wave generated by a CFD approach.

CFD simulation of vortex-induced vibration of free-standing hybrid riser

Cao, Yi,Chen, Hamn-Ching Techno-Press 2017 Ocean systems engineering Vol.7 No.3

This paper presents 3D numerical simulations of a Free Standing Hybrid Riser under Vortex Induced Vibration, with prescribed motion on the top to replace the motion of the buoyancy can. The model is calculated using a fully implicit discretization scheme. The flow field around the riser is computed by solving the Navier-Stokes equations numerically. The fluid domain is discretized using the overset grid approach. Grid points in near-wall regions of riser are of high resolution, while far field flow is in relatively coarse grid. Fluid-structure interaction is accomplished by communication between fluid solver and riser motion solver. Simulation is based on previous experimental data. Two cases are studied with different current speeds, where the motion of the buoyancy can is approximated to a 'banana' shape. A fully three-dimensional CFD approach for VIV simulation for a top side moving Riser has been presented. This paper also presents a simulation of a riser connected to a platform under harmonic regular waves.

CFD simulations of a performance-scaled wind turbine

Ye, Maokun,Chen, Hamn-Ching,Koop, Arjen Techno-Press 2022 Ocean systems engineering Vol.12 No.2

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 - ω SST turbulence model is adopted in the incompressible Reynolds Averaged Navier-Stokes (RANS) simulations. First, the thrust and torque coefficients, C_T and C_P, 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.

Numerical simulation of wave slamming on 3D offshore platform deck using a coupled Level-Set and Volume-of-Fluid method for overset grid system

Zhao, Yucheng,Chen, Hamn-Ching,Yu, Xiaochuan Techno-Press 2015 Ocean systems engineering Vol.5 No.4

The numerical simulation of wave slamming on a 3D platform deck was investigated using a coupled Level-Set and Volume-of-Fluid (CLSVOF) method for overset grid system incorporated into the Finite-Analytic Navier-Stokes (FANS) method. The predicted slamming impact forces were compared with the corresponding experimental data. The comparisons showed that the CLSVOF method is capable of accurately predicting the slamming impact and capturing the violent free surface flow including wave slamming, wave inundation and wave recession. Moreover, the capability of the present CLSVOF method for overset grid system is a prominent feature to handle the prediction of wave slamming on offshore structure.

VIV simulation of riser-conductor systems including nonlinear soil-structure interactions

Ye, Maokun,Chen, Hamn-Ching Techno-Press 2019 Ocean systems engineering Vol.9 No.3

This paper presents a fully three-dimensional numerical approach for analyzing deepwater drilling riser-conductor system vortex-induced vibrations (VIV) including nonlinear soil-structure interactions (SSI). The drilling riser-conductor system is modeled as a tensioned beam with linearly distributed tension and is solved by a fully implicit discretization scheme. The fluid field around the riser-conductor system is obtained by Finite-Analytic Navier-Stokes (FANS) code, which numerically solves the unsteady Navier-Stokes equations. The SSI is considered by modeling the lateral soil resistance force according to nonlinear p-y curves. Overset grid method is adopted to mesh the fluid domain. A partitioned fluid-structure interaction (FSI) method is achieved by communication between the fluid solver and riser motion solver. A riser-conductor system VIV simulation without SSI is firstly presented and served as a benchmark case for the subsequent simulations. Two SSI models based on a nonlinear p-y curve are then applied to the VIV simulations. Also, the effects of two key soil properties on the VIV simulations of riser-conductor systems are studied.

Coupled CFD-FEM simulation of hydrodynamic responses of a CALM buoy

Gu, Haoyuan,Chen, Hamn-Ching,Zhao, Linyue Techno-Press 2019 Ocean systems engineering Vol.9 No.1

In this paper, the Finite-Analytic Navier-Stokes (FANS) code is coupled with an in-house finite-element code to study the dynamic interaction between a floating buoy and its mooring system. Hydrodynamic loads on the buoy are predicted with the FANS module, in which Large Eddy Simulation (LES) is used as the turbulence model. The mooring lines are modeled based on a slender body theory. Their dynamic responses are simulated with a nonlinear finite element module, MOORING3D. The two modules are coupled by transferring the forces and displacements of the buoy and its mooring system at their connections through an interface module. A free-decay model test was used to calibrate the coupled method. In addition, to investigate the capability of the present coupled method, numerical simulations of two degree-of-freedom vortex-induced motion of a CALM buoy in uniform currents were performed. With the study it can be verified that accurate predictions of the motion responses and tension responses of the CALM buoy system can be made with the coupling CFD-FEM method.