Maneuvering in Waves

Ships, buoys, barges, floating docks, breakwaters, submersibles supporting oil drilling rigs, and so on, are all structures whose safety and performance depend on their response to waves. In a calm sea, the body weight, the buoyancy force, and possible forces from external constraints such as ten- sion legs, keep the body in static equilibrium. In waves, the presence of a sufficiently large body causes diffraction (scattering) of waves. The body must absorb some of the incident wave momentum and therefore must suffer a dynamic force. If the constraints, such as the mooring lines, are not sufficiently rigid, the body oscillates, hence further radiates waves, and ex- periences reacting forces from the surrounding fluid and from the constraint. Since the reacting forces depend on the motion of the body itself, the body, the constraint, and the surrounding water are dynamically coupled in the presence of incoming waves. from: THEORY AND APPLICATIONS OF OCEAN SURFACE WAVES i...

Dynamic of...

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Ok... undertood. why the name is pie for symbol (π)? to my understanding, π is representing half of the cake ( it is like apam balik, half of the cake). So, the condition of : 1. when a cake (2π) is slice by 12 parts, then each person will get one slice with 30deg. Or in other words, 2π is divided to 12. (2π/12 = π/6).  2. Next, if slice by 8, so each will get π/4 portion with 45deg. Where the value of π as initially known value is 3.142 ( short from the long list). Ok... now, if we go for π, then for π/6, then 3.142/6= 0.524.  This value of 0.524 is in we called as radian.  Why we use radian? because it will represent the location in x, y direction from the 0 deg at first axis. 3. Here is the important remark. Let see on the π/3, if we look closely we will notice that the "trend" of the increasing of number of "slice".  It is π/3,  2π/3,  3π/3(which only denote as π),   4π/3 and lastly  5π/3.   If we see othe...

source document :   source : SNAME vol ii components: 1. Frictional resistance: due to motion of hull through a fluid that is its character is viscous 2. wave-making resistance: due to the energy that additionally must be supplied continuously by the ship to the wave system. The so called "wave system" was created on the water surface. 3. eddy resistance: energy that carried away. That energy due to eddies shed from the hull + appendages. 4.  Air resistance. Note :  normally there is another name, which is called as "residuary resistance". It is the combination of wave-making and eddy resistance. 

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) 

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".

1. When discussing the ship maneuvering in waves, it should consider irregular waves to represent actual seaway. 2. The task of naval architect is to ensure (within the limits of other design requirements): the hull form and propulsion arrangement as much as possible to be efficient in the hydrodynamic sense the ultimate test is that the ship shall perform, at the required speed with the minimum of shaft power here, the problem is to attain the best combination of low resistance and high propulsive efficiency. in general, this ( "attain the best combination of  low resistance  and  high propulsive efficiency "  ) can only be attained by a proper matching of hull and propeller. 3. Therefore, before we go to explore what best match of hull and propeller, in order to assess and examine the ship maneuvering in irregular waves, it is mandatory to back one step - should attain the best combination of low resistance and propulsive - and investigate the effect of...

Reference from SNAME on naval architecture Principles of Naval Architecture (Vol I) Second revision Principles of Naval Architecture (Vol II) Second Revision

Total resistance components

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. ...