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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
International Journal of Naval Architecture and Ocean Engineering
Journal Basic Information
Journal DOI :
The Society of Naval Architects of Korea
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Volume & Issues
Volume 2, Issue 4 - Dec 2010
Volume 2, Issue 3 - Sep 2010
Volume 2, Issue 2 - Jun 2010
Volume 2, Issue 1 - Mar 2010
Selecting the target year
Comparative study on the performance of Pod type waterjet by experiment and computation
Kim, Moon-Chan ; Park, Warn-Gyu ; Chun, Ho-Hwan ; Jung, Un-Hwa ;
International Journal of Naval Architecture and Ocean Engineering, volume 2, issue 1, 2010, Pages 1~13
DOI : 10.3744/JNAOE.2010.2.1.001
A comparative study between a computation and an experiment has been conducted to predict the performance of a Pod type waterjet for cm amphibious wheeled vehicle. The Pod type waterjet has been chosen on the basis of the required specific speed of more than 2500. As the Pod type waterjet is an extreme type of axial flow type waterjet, theoretical as well as experimental works about Pod type waterjets are very rare. The main purpose of the present study is to validate and compare to the experimental results of the Pod type waterjet with the developed CFD in-house code based on the RANS equations. The developed code has been validated by comparing with the experimental results of the well-known turbine problem. The validation also extended to the flush type waterjet where the pressures along the duct surface and also velocities at nozzle area have been compared with experimental results. The Pod type waterjet has been designed and the performance of the designed waterjet system including duct, impeller and stator was analyzed by the previously mentioned m-house CFD Code. The pressure distributions and limiting streamlines on the blade surfaces were computed to confirm the performance of the designed waterjets. In addition, the torque and momentum were computed to find the entire efficiency and these were compared with the model test results. Measurements were taken of the flow rate at the nozzle exit, static pressure at the various sections along the duct and also the nozzle, revolution of the impeller, torque, thrust and towing forces at various advance speed's for the prediction of performance as well as for comparison with the computations. Based on these measurements, the performance was analyzed according to the ITTC96 standard analysis method. The full-scale effective and the delivered power of the wheeled vehicle were estimated for the prediction of the service speed. This paper emphasizes the confirmation of the ITTC96 analysis method and the developed analysis code for the design and analysis of the Pod type waterjet system.
Development of a three dimensional circulation model based on fractional step method
Abualtayef, Mazen ; Kuroiwa, Masamitsu ; Sief, Ahmed Khaled ; Matsubara, Yuhei ; Aly, Ahmed M. ; Sayed, Ahmed A. ; Sambe, Alioune Nar ;
International Journal of Naval Architecture and Ocean Engineering, volume 2, issue 1, 2010, Pages 14~23
DOI : 10.3744/JNAOE.2010.2.1.014
A numerical model was developed for simulating a three-dimensional multilayer hydrodynamic and thermodynamic model in domains with irregular bottom topography. The model was designed for examining the interactions between flow and topography. The model was based on the three-dimensional Navier-Stokes equations and was solved using the fractional step method, which combines the finite difference method in the horizontal plane and the finite element method in the vertical plane. The numerical techniques were described and the model test and application were presented. For the model application to the northern part of Ariake Sea, the hydrodynamic and thermodynamic results were predicted. The numerically predicted amplitudes and phase angles were well consistent with the field observations.
Experimental evaluation of pumpjet propulsor for an axisymmetric body in wind tunnel
Suryanarayana, Ch. ; Satyanarayana, B. ; Ramji, K. ; Saiju, A. ;
International Journal of Naval Architecture and Ocean Engineering, volume 2, issue 1, 2010, Pages 24~33
DOI : 10.3744/JNAOE.2010.2.1.024
Design of a Pump Jet Propulsor (PJP) was undertaken for an underwater body with axisymmetric configuration using axial/low compressor design techniques supported by Computational Fluid Dynamics (CFD) analysis for performance prediction. Experimental evaluation of the PJP was earned out through experiments in a Wind Tunnel Facility (WTF) using momentum defect principle for propulsive performance prior to proceeding with extensive experimental evaluation in towing tank and cavitation tunnel. Experiments were particularly conducted with respect to Self Propulsion Point (SPP), residual torque and thrust characteristics over a range of vehicle advance ratio in order to ascertain whether sufficient thrust is developed at the design condition with least possible imbalance torque left out due to residual swirl in the slip stream. Pumpjet and body models were developed for the propulsion tests using Aluminum alloy forged material. Tests were conducted from 0 m/s to 30 m/s at four rotational speeds of the PJP. SPP was determined confirming the thrust development capability of PJP. Estimation of residual torque was carried out at SPP corresponding to speeds of 15, 20 and 25 m/s to examine the effectiveness of the stator. Estimation of thrust and residual torque was also carried out at wind speeds 0 and 6 m/s for PJP RPMs corresponding to self propulsion tests to study the propulsion characteristics during the launch of the vehicle m water where advance ratios are close to Zero. These results are essential to assess the thrust performance at very low advance ratios to accelerate the body and to control the body during initial stages. This technique has turned out to be very useful and economical method for quick assessment of overall performance of the propulsor and generation of exhaustive fluid dynamic data to validate CFD techniques employed.
Field investigations on port non-tranquility caused by infra-gravity water waves
Najafi-Jilani, A. ; Rahimi-Maleki, D. ;
International Journal of Naval Architecture and Ocean Engineering, volume 2, issue 1, 2010, Pages 34~38
DOI : 10.3744/JNAOE.2010.2.1.034
Field investigations have been carried out in two 60-day stages on the surf beat low frequency waves in Anzali port, one of the main commercial ports in Iran, located in southwest coast of the Caspian Sea. The characteristics of significant water waves were measured at three metering stations in the sea, one at the entrance of the port and three in the basin. The measured data were inspected to investigate the surf beat negative effects on the tranquility of the port. Using field measurements and complementary numerical modeling, the response of the basin to the infra-gravity long waves was inspected for a range of wave frequencies. It was concluded that the water surface fluctuations in the port is strongly related to the incident wave period. The long waves with periods of about 45s were recognized as the worst cases for water surfaceperturbation in the port. For wave periods higher than the mentioned range, the order of fluctuation was generally low.
Experimental and numerical studies on super-cavitating flow of axisymmetric cavitators
Ahn, Byoung-Kwon ; Lee, Chang-Sup ; Kim, Hyoung-Tae ;
International Journal of Naval Architecture and Ocean Engineering, volume 2, issue 1, 2010, Pages 39~44
DOI : 10.3744/JNAOE.2010.2.1.039
Recently underwater systems moving at high speed such as a super-cavitating torpedo have been studied for their practical advantage of the dramatic drag reduction. In this study we are focusing our attention on super-cavitating flows around axisymmetric cavitators. A numerical method based on inviscid flow is developed and the results for several shapes of the cavitator are presented. First using a potential based boundary element method, we find the shape of the cavtiator yielding a sufficiently large enough cavity to surround the body. Second, numerical predictions of supercavity are validated by comparing, with experimental observations carried out in a high speed cavitation tunnel at Chungnam National University (CNU CT).
Effect of fabrication processes on mechanical properties of glass fiber reinforced polymer composites for 49 meter (160 foot) recreational yachts
Kim, Dave Dae-Wook ; Hennigan, Daniel John ; Beavers, Kevin Daniel ;
International Journal of Naval Architecture and Ocean Engineering, volume 2, issue 1, 2010, Pages 45~56
DOI : 10.3744/JNAOE.2010.2.1.045
Polymer composite materials offer high strength and stiffness to weight ratio, corrosion resistance, and total life cost reductions that appeal to the marine industry. The advantages of composite construction have led to their incorporation in U.S. yacht hull structures over 46 meters (150 feet) in length. In order to construct even larger hull structures, higher quality composites with lower cost production techniques need to be developed. In this study, the effect of composite hull fabrication processes on mechanical properties of glass fiber reinforced plastic (GFRP) composites is presented. Fabrication techniques investigated during this study are hand lay-up (HL), vacuum infusion (VI), and hybrid (HL+VI) processes. Mechanical property testing includes: tensile, compressive, and ignition loss sample analysis. Results demonstrate that the vacuum pressure implemented dining composite fabrication has an effect on mechanical properties. The VI processed GFRP yields improved mechanical properties in tension/compression strengths and tensile modulus. The hybrid GFRP composites, however, failed in a sequential manor, due to dissimilar failure modes in the HL and VI processed sides. Fractography analysis was conducted to validate the mechanical property testing results.