Numerical Analysis and Experimental Validation of Added Resistance on Ship in Waves

2019 ◽  
Vol 63 (4) ◽  
pp. 268-282
Author(s):  
Yonghwan Kim ◽  
Dong-Min Park ◽  
Jae-Hoon Lee ◽  
Jaehoon Lee ◽  
Byung-Soo Kim ◽  
...  
Keyword(s):  
Momentum Conservation ◽  
Numerical Results ◽  
Added Resistance ◽  
Irregular Wave ◽  
Numerical Studies ◽  
Motion Responses ◽  
Calm Water ◽  
National University ◽  
The Difference ◽  
Seoul National University

In this study, the added resistance of a liquefied natural gas carrier (LNGC) in the presence of waves is studied experimentally and numerically.The ship model is an LNGC designed by Samsung Heavy Industries (SHI). Experiments on ship motion responses and added resistance under head sea conditions were conducted at the Seoul National University and SHI. The influences of the experimental methods (captive and self-propulsion methods), incident wave amplitude, and regular and irregular wave conditions on the added resistance are evaluated using the same model ship set at different scales. In the numerical studies, the motion responses and added resistance are obtained using three methods—the strip method by adopting momentum conservation; Rankine panel method using pressure integration; and computational fluid dynamics method, using the difference in the resistances in waves and calm water. The experimental and numerical results under various conditions are compared, and the characteristics of the experimental and numerical results are discussed.

The Effect of Pitch Gyradius on Added Resistance of Yacht Hulls

1991 ◽  
Author(s):  
James F. Moran
Keyword(s):  
Water Resistance ◽  
Wave Spectrum ◽  
Response Amplitude ◽  
Added Resistance ◽  
Regular Waves ◽  
Low Frequencies ◽  
Irregular Wave ◽  
Wave Data ◽  
The Difference ◽  
Response Amplitude Operators

The purpose of this investigation was to determine the effect of pitch gyradius on added resistance of yacht hulls. Tank testing of a model yacht in head seas was performed in the Webb Robinson Model Basin. The model was tested in regular waves at two speeds and five variations of gyradius. The model was also evaluated in irregular seas of the Pierson-Moskowitz spectrum at various speeds with two gyradii. Response Amplitude Operators were developed from the regular wave data and comparisons made. The irregular wave data were analyzed for the effect of speed on the difference in added resistance between the maximum and minimum gyradius settings. Several conclusions were arrived at after analyzing the data. The Response Amplitude Operaters shift as the gyradius changes. In regular waves, at low frequencies of encounter, a lower, gyradius resulted in less added frequencies of encounter in regular waves, this trend reverses itself and the higher gyradii result in reduced added resistance. However, at higher frequencies of encounter in regular waves, this trend reverses, reverses itself in reduced added resistance. The peaks of the RAO curves shift to higher frequencies at higher gyradii. It was also concluded that at the higher speed, Froude Number of 0.3, the added resistance was lower relative to the still-water resistance for each gyradius tested. The irregular wave testing revealed the effect of the lower frequencies dominating the irregular wave spectrum. The minimum gyradius, in irregular seas showed less added resistance than the maximum gyradius. In addition, the irregular wave testing verified, the reduction of added resistance, relative to still-water resistance, at increasing speeds for both the minimum and maximum gyradii.

Numerical Analysis on Added Resistance of Ship by 3-D Green Function Method

2006 ◽  
Author(s):  
Yoshiyuki Inoue ◽  
N. M. Golam Zakaria
Keyword(s):  
Experimental Data ◽  
Numerical Analysis ◽  
Green Function ◽  
Function Method ◽  
Numerical Results ◽  
Numerical Code ◽  
Added Resistance ◽  
Green Function Method ◽  
Total Potential ◽  
Motion Responses

This paper deals with the numerical analysis on added resistance of a ship by 3-D Green Function Method. Linear potential theory has been used to describe the fluid motion and 3-D sink-source technique with forward speed has been applied to determine hydrodynamic forces for surface ship advancing in waves at constant speed. After solving the motion equation in frequency domain, radiation potential due to motion responses have been calculated to obtain the total potential of the flow field. Then, total potential and its derivatives have been obtained to assess the added resistance in waves by near field approach. To show the validity of the numerical code, the present numerical results for motion responses and wave loads on ships have been compared with experimental data as well as some numerical results by different approaches. Then the added resistances given by present numerical calculation by 3-D Green Function have been compared with some classical 2-D methods as well as experimental data for Series 60 ships. Finally the present numerical calculations have been applied for fuller form slow speed vessel where the classical 2-D methods usually fails to give good results due to their inherent limitations. The numerical results suggest that better agreement have been achieved in many cases using present full 3-D Green Function method.

scholarly journals Full-Scale CFD Analysis of Double-M Craft Seakeeping Performance in Regular Head Waves

2021 ◽  
Vol 9 (5) ◽  
pp. 504
Author(s):  
Deniz Ozturk ◽  
Cihad Delen ◽  
Simone Mancini ◽  
Mehmet Ozan Serifoglu ◽  
Turgay Hizarci
Keyword(s):  
Full Scale ◽  
Stokes Wave ◽  
Added Resistance ◽  
Motion Responses ◽  
Seakeeping Performance ◽  
Head Waves ◽  
Calm Water ◽  
Maximum Improvement ◽  
Fifth Order ◽  
Regular Head Waves

This study presents the full-scale resistance and seakeeping performance of an awarded Double-M craft designed as a 15 m next-generation Emergency Response and Rescue Vessel (ERRV). For this purpose, the Double-M craft is designed by comprising the benchmark Delft 372 catamaran with an additional center and two side hulls. First, the resistance and seakeeping analyses of Delft 372 catamaran are simulated on the model scale to verify and compare the numerical setup for Fr = 0.7. Second, the seakeeping performance of the full-scale Double-M craft is examined at Fr = 0.7 in regular head waves (λ/L = 1 to 2.5) for added resistance and 2-DOF motion responses. The turbulent flow is simulated by the unsteady RANS method with the Realizable Two-Layer k-ε scheme. The calm water is represented by the flat VOF (Volume of Fluid) wave, while the incident long waves are represented by the fifth-order Stokes wave. The residual resistance of the Double-M craft is improved by 2.45% compared to that of the Delft 372 catamaran. In the case of maximum improvement (at λ/L = 1.50), the relative added resistance of the Double-M craft is 10.34% lower than the Delft 372 catamaran; moreover, the heave and pitch motion responses were 72.5% and 35.5% less, respectively.

scholarly journals Optimization of Solar Panel Orientation Considering Temporal Volatility and Scenario-Based Photovoltaic Potential: A Case Study in Seoul National University

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3262 ◽  
Author(s):  
Myeongchan Oh ◽  
Hyeong-Dong Park
Keyword(s):  
Solar Panels ◽  
University Campuses ◽  
Optimal Orientation ◽  
Total Potential ◽  
National University ◽  
The Difference ◽  
Seoul National University ◽  
The Stability ◽  
Project Objectives ◽  
The University

University campuses accommodate large numbers of people and are suitable places to organize a microgrid. The solar potential in the university area is estimated and the optimal orientation of solar panels is presented in this study. The optimal orientation is analyzed considering temporal volatility to increase the stability of the grid. Several variables are selected and scenarios are designed to consider various investments and technologies. Scenario-specific photovoltaic potentials were estimated using Geographic Information Systems analysis technology. Analysis of temporal volatility was conducted based on the difference between demand and supply of electricity. Optimal panel orientations were presented according to project objectives, such as highest efficiency or low volatility. As a result, the total potential of the study area was tens to hundreds of GWh/year depending on the scenario. The university has an advantage in hourly volatility, but has some problems in monthly volatility. The optimal orientation varies according to objectives and solar power supply ratio. The results of this study are expected to help researchers and technicians in the solar energy industry and assist in urban planning.

scholarly journals Predictors of cervical myelopathy and hydrocephalus in young children with achondroplasia

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Youngbo Shim ◽  
Jung Min Ko ◽  
Tae-Joon Cho ◽  
Seung‐Ki Kim ◽  
Ji Hoon Phi
Keyword(s):  
Magnetic Resonance Imaging ◽  
Young Children ◽  
Cervical Myelopathy ◽  
Treatment Method ◽  
Foramen Magnum ◽  
Resonance Imaging ◽  
Timely Manner ◽  
Frontal Horn ◽  
National University ◽  
Seoul National University

Abstract Background Cervical myelopathy and hydrocephalus occasionally occur in young children with achondroplasia. However, these conditions are not evaluated in a timely manner in many cases. The current study presents significant predictors for cervical myelopathy and hydrocephalus in young children with achondroplasia. Methods A retrospective analysis of 65 patients with achondroplasia who visited Seoul National University Children’s Hospital since 2012 was performed. The patients were divided into groups according to the presence of cervical myelopathy and hydrocephalus, and differences in foramen magnum parameters and ventricular parameters by magnetic resonance imaging between groups were analyzed. Predictors for cervical myelopathy and hydrocephalus were analyzed, and the cut-off points for significant ones were calculated. Results The group with cervical myelopathy showed foramen magnum parameters that indicated significantly lower cord thickness than in the group without cervical myelopathy, and the group with hydrocephalus showed significantly higher ventricular parameters and ‘Posterior indentation’ grade than the group without hydrocephalus. ‘Cord constriction ratio’ (OR 5199.90, p = 0.001) for cervical myelopathy and ‘Frontal horn width’ (OR 1.14, p = 0.001) and ‘Posterior indentation’ grade (grade 1: OR 9.25, p = 0.06; grade 2: OR 18.50, p = 0.01) for hydrocephalus were significant predictors. The cut-off points for cervical myelopathy were ‘Cord constriction ratio’ of 0.25 and ‘FM AP’ of 8 mm (AUC 0.821 and 0.862, respectively) and ‘Frontal horn width’ of 50 mm and ‘Posterior indentation’ grade of 0 (AUC 0.788 and 0.758, respectively) for hydrocephalus. Conclusion ‘Cord constriction ratio’ for cervical myelopathy and ‘Frontal horn width’ and ‘Posterior indentation’ grade for hydrocephalus were significant predictors and may be used as useful parameters for management. ‘Posterior indentation’ grade may also be used to determine the treatment method for hydrocephalus.

scholarly journals Components of Metabolic Syndrome in Korean Adults: A Hospital-Based Cohort at Seoul National University Bundang Hospital

2019 ◽  
Vol 28 (2) ◽  
pp. 118-128 ◽  
Author(s):  
Soo Lim ◽  
Se Hee Min ◽  
Ji Hyun Lee ◽  
Lee Kyung Kim ◽  
Dong-Hwa Lee ◽  
...  
Keyword(s):  
Metabolic Syndrome ◽  
Korean Adults ◽  
National University ◽  
Seoul National University

Experimental and Numerical Study on Grinding Temperature during Surface Grinding with Different Cooling Methods

2009 ◽  
Vol 416 ◽  
pp. 514-518 ◽  
Author(s):  
Qing Long An ◽  
Yu Can Fu ◽  
Jiu Hua Xu
Keyword(s):  
Numerical Study ◽  
Specific Energy Consumption ◽  
Ground Surface ◽  
Numerical Results ◽  
Surface Grinding ◽  
Grinding Temperature ◽  
Air Jet ◽  
The Difference ◽  
High Specific Energy ◽  
Cooling Methods

Grinding, characterized by its high specific energy consumption, may generate high grinding zone temperature. These can cause thermal damage to the ground surface and poor surface integrity, especially in the grinding of difficult-to-machine materials. In this paper, experimental and fem study on grinding temperature during surface grinding of Ti-6Al-4V with different cooling methods. A comparison between the experimental and numerical results is made. It is indicated that the difference between experimental and numerical results is below 15% and the numerical results can be considered reliable. Grinding temperature can be more effectively reduced with CPMJ than that with cold air jet and flood cooling method.

EFD and CFD Study of Forces, Ship Motions, and Flow Field for KRISO Container Ship Model in Waves

2020 ◽  
Vol 64 (01) ◽  
pp. 61-80
Author(s):  
Ping-Chen Wu ◽  
Md. Alfaz Hossain ◽  
Naoki Kawakami ◽  
Kento Tamaki ◽  
Htike Aung Kyaw ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Flow Field ◽  
Flow Simulation ◽  
Wake Flow ◽  
Ship Motions ◽  
Container Ship ◽  
Added Resistance ◽  
Ocean Engineering ◽  
Ship Model ◽  
Calm Water

Ship motion responses and added resistance in waves have been predicted by a wide variety of computational tools. However, validation of the computational flow field still remains a challenge. In the previous study, the flow field around the Korea Research Institute for Ships and Ocean Engineering (KRISO) Very Large Crude-oil Carrier 2 tanker model with and without propeller condition and without rudder condition was measured by the authors, as well as the resistance and self-propulsion tests in waves. In this study, the KRISO container ship model appended with a rudder was used for the higher Froude number .26 and smaller block coefficient .65. The experiments were conducted in the Osaka University towing tank using a 3.2-m-long ship model for resistance and self-propulsion tests in waves. Viscous flow simulation was performed by using CFDShip-Iowa. The wave conditions proposed in Computational Fluid Dynamics (CFD) Workshop 2015 were considered, i.e., the wave-ship length ratio λ/L = .65, .85, 1.15, 1.37, 1.95, and calm water. The objective of this study was to validate CFD results by Experimental Fluid Dynamics (EFD) data for ship vertical motions, added resistance, and wake flow field. The detailed flow field for nominal wake and self-propulsion condition will be analyzed for λ/L = .65, 1.15, 1.37, and calm water. Furthermore, bilge vortex movement and boundary layer development on propeller plane, propeller thrust, and wake factor oscillation in waves will be studied.

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