The Experts below are selected from a list of 156 Experts worldwide ranked by ideXlab platform

L Raheja - One of the best experts on this subject based on the ideXlab platform.

  • On Submerged Stagnation Points and Bow Vortices Generation
    2001
    Co-Authors: L Raheja
    Abstract:

    The mechanism of the generation of bow vortices in two dimensions, in laboratory scale, is explained on the basis of the existence of a submerged stagnation point below the free surface. The stream which originates from the submerged stagnation point in the free surface direction reverses and neutralizes the momentum of incoming flow resulting in a free surface separation point. The initial location of the submerged stagnation point and subsequently the free surface separation point is calculated for the case of a semisubmerged horizontal circular cylinder, and the latter is compared with the experimental results. The agreement is reasonably good. The generation of bow vortices is discussed as a balance between inertial and gravitational effects. The loss of pressure at the bow and the consequent drag due to bow vortices phenomena is calculated and is found to agree well with the value found by experiment. A methodology for the design of efficient bow contour shape in two dimensions where the submerged stagnation point is used as a control handle, is presented. The theory is also applied to non-regular shapes like vertical step and bulbous bow. The results are compared with those obtained by flow computation and found to be in reasonably close agreement. Finally, a conjecture is advanced to explain the generation of bow vortices in three dimensions, i.e. the necklace vortex around a ship's Load Waterline, on the same basis.

Jongdeok Choi - One of the best experts on this subject based on the ideXlab platform.

  • a study on the design of nozzle propeller for trawler
    Bulletin of The Korean Society of Fisheries Technology, 2008
    Co-Authors: Seongjae Jeong, Jinkeun Hong, Jongdeok Choi
    Abstract:

    Trawlers have to a sufficient towing force due to its characteristics of the high performance. The newlyconstructed trawler with the conventional propellers shows the sufficient towing force, so that the propellerand engine are optimized. In the 1970s, many trawlers were imported from overseas by Korean fisheriesindustries. But the engine output degradation with year by year caused the trawlers to decrease the towingspeed of the vessels. On the previous studies, the nozzle propeller had not so good efficiency with increasingof resistance in high-speed cruising operation over 15knots. But the trawling operation is just required thehigher thrust and towing force, so that the nozzle propeller is very profitable for the its effectiveness. A newnozzle propeller was designed for the 4,462G/T trawler, Dong-San, operated by Dongwon Industries Co.,Ltd. to improve the towing speed, and the model tests were performed. The model ship and model propellerare preciously manufactured and used model tests in basin. The resistance test and propeller open water testwere performed for the cases of the half and full Loads. The required engine horse power and RPM wereevaluated analytically by the speed-power curve, when the trawler was equipped with the nozzle propeller.The results of tests showed that the towing speed 4.85knots on the design Load Waterline requires the 200engine RPM and 2,567ps in the delivered horsepower.Key words : Trawler, Ducted propeller(Kort nozzle propeller), Design

Seongjae Jeong - One of the best experts on this subject based on the ideXlab platform.

  • a study on the design of nozzle propeller for trawler
    Bulletin of The Korean Society of Fisheries Technology, 2008
    Co-Authors: Seongjae Jeong, Jinkeun Hong, Jongdeok Choi
    Abstract:

    Trawlers have to a sufficient towing force due to its characteristics of the high performance. The newlyconstructed trawler with the conventional propellers shows the sufficient towing force, so that the propellerand engine are optimized. In the 1970s, many trawlers were imported from overseas by Korean fisheriesindustries. But the engine output degradation with year by year caused the trawlers to decrease the towingspeed of the vessels. On the previous studies, the nozzle propeller had not so good efficiency with increasingof resistance in high-speed cruising operation over 15knots. But the trawling operation is just required thehigher thrust and towing force, so that the nozzle propeller is very profitable for the its effectiveness. A newnozzle propeller was designed for the 4,462G/T trawler, Dong-San, operated by Dongwon Industries Co.,Ltd. to improve the towing speed, and the model tests were performed. The model ship and model propellerare preciously manufactured and used model tests in basin. The resistance test and propeller open water testwere performed for the cases of the half and full Loads. The required engine horse power and RPM wereevaluated analytically by the speed-power curve, when the trawler was equipped with the nozzle propeller.The results of tests showed that the towing speed 4.85knots on the design Load Waterline requires the 200engine RPM and 2,567ps in the delivered horsepower.Key words : Trawler, Ducted propeller(Kort nozzle propeller), Design

Jinkeun Hong - One of the best experts on this subject based on the ideXlab platform.

  • a study on the design of nozzle propeller for trawler
    Bulletin of The Korean Society of Fisheries Technology, 2008
    Co-Authors: Seongjae Jeong, Jinkeun Hong, Jongdeok Choi
    Abstract:

    Trawlers have to a sufficient towing force due to its characteristics of the high performance. The newlyconstructed trawler with the conventional propellers shows the sufficient towing force, so that the propellerand engine are optimized. In the 1970s, many trawlers were imported from overseas by Korean fisheriesindustries. But the engine output degradation with year by year caused the trawlers to decrease the towingspeed of the vessels. On the previous studies, the nozzle propeller had not so good efficiency with increasingof resistance in high-speed cruising operation over 15knots. But the trawling operation is just required thehigher thrust and towing force, so that the nozzle propeller is very profitable for the its effectiveness. A newnozzle propeller was designed for the 4,462G/T trawler, Dong-San, operated by Dongwon Industries Co.,Ltd. to improve the towing speed, and the model tests were performed. The model ship and model propellerare preciously manufactured and used model tests in basin. The resistance test and propeller open water testwere performed for the cases of the half and full Loads. The required engine horse power and RPM wereevaluated analytically by the speed-power curve, when the trawler was equipped with the nozzle propeller.The results of tests showed that the towing speed 4.85knots on the design Load Waterline requires the 200engine RPM and 2,567ps in the delivered horsepower.Key words : Trawler, Ducted propeller(Kort nozzle propeller), Design