total resistance

Total resistance components




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Asas Maneuvering Modeling Group (MMG)

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source:   MMG 3D philosophy of theory behind MMG : THESIS   ( from p. 39 to 46) This note will explain in brief, simple but sufficient to understand the story behind MMG and how to understand it. Starts with: 1.  Coordinate systems 2.  Motion equations 3.  Hydrodynamic forces - acting on hull, force by propulsion and forces by steering. 4.  Tests for obtaining the coefficients: RFT - in straight moving with B = 0 (  hull drift angle equal 0). OTT - the ship is towed in oblique. (  B is not 0. ).   This OTT is performed with r' = 0  where there is no yawing involved. CMT -  the ship model is kept captive and towed at certain  r'  yawing  rate.  The rate is covered normally from 0.2, 0.6 and 0.8. RFT - in oblique towing and steady turning. This test is to obtain flow straightening coefficient test. ----------------- In calculating hydrodynamic derivatives, LSM is applied. ...
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how propeller works - impulse theory

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source: file.pdf impulse theory is the most basic to propel a ship in the impulse theory, the pressure is changing. Low pressure is before, and high pressure after blades. And the pressure become stabilized at certain time. ( basic: bernoulli law - pressure velocity stuffs) 
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continuity law and bernoulli law in maneuvering

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In simple explanation, when there is increment of water speed at stern part ( due to reduced area - according to continuity law -  assuming contant Axv) then  after that bernoulli law take places ( assuming constant stern and bow part). The stern part (where the water speed became increased) now will cause low pressure at that area and meantime high pressure at bow. This difference in the pressure cause the ship to experience " bank suction".
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