Marine Hydrodynamics
Marine hydrodynamics covers hydrodynamics on an offshore or coastal structure itself and on related marine facilities such as mooring lines, riser pipes, propellers, rudders, and so on. Among them, we focus only on hydrodynamics on a floating structure and slender line structures such as mooring lines and riser pipes. Generally speaking, linear phenomena are dominant for dynamics of a floating structure except in cases of catastrophic phenomena such as capsizing. Linear hydrodynamic force is important as it relates to an ideal fluid. Of course, nonlinear hydrodynamic forces such as drag force or viscous damping force are important in some cases, but we can treat them independently. The free surface makes this ideal fluid phenomenon more interesting. The general ocean waves are unsteady, irregular, and directional. We need to know not only the wave excitation force, but also the reaction hydrodynamic force due to oscillation of a structure (so-called radiation force, such as added mass or wave-making damping force). Drag force is important for a bluff body, riser string, or mooring line in wind and current.
Lift force is important for a vessel and a deck of a semisubmersible in wind, and for a vessel in current. Drag force is also important for a line structure such as riser pipes in waves, which behave like oscillating flow. Drag force is caused mainly by separated flow in viscous fluid. Drag force is a function of the Reynolds number and surface roughness of a body, and the Keulegan-Carpenter number, especially in oscillating flow. A bilge keel of a general vessel produces mainly drag force, which acts as a damping force to reduce the roll motion of a vessel. Hydrodynamics of an ideal fluid is described in detail by Newman [12], Mei [11], and Faltinsen [8]. Viscous force such as drag force is treated in detail by Hoerner [9] and Sarpkaya and Isaacson [14]. General hydrodynamics for offshore structures is explained by Chakrabarti [4], and Clauss, Lehman, and Oestergaard [5].
Marine hydrodynamics covers hydrodynamics on an offshore or coastal structure itself and on related marine facilities such as mooring lines, riser pipes, propellers, rudders, and so on. Among them, we focus only on hydrodynamics on a floating structure and slender line structures such as mooring lines and riser pipes. Generally speaking, linear phenomena are dominant for dynamics of a floating structure except in cases of catastrophic phenomena such as capsizing. Linear hydrodynamic force is important as it relates to an ideal fluid. Of course, nonlinear hydrodynamic forces such as drag force or viscous damping force are important in some cases, but we can treat them independently. The free surface makes this ideal fluid phenomenon more interesting. The general ocean waves are unsteady, irregular, and directional. We need to know not only the wave excitation force, but also the reaction hydrodynamic force due to oscillation of a structure (so-called radiation force, such as added mass or wave-making damping force). Drag force is important for a bluff body, riser string, or mooring line in wind and current.
Lift force is important for a vessel and a deck of a semisubmersible in wind, and for a vessel in current. Drag force is also important for a line structure such as riser pipes in waves, which behave like oscillating flow. Drag force is caused mainly by separated flow in viscous fluid. Drag force is a function of the Reynolds number and surface roughness of a body, and the Keulegan-Carpenter number, especially in oscillating flow. A bilge keel of a general vessel produces mainly drag force, which acts as a damping force to reduce the roll motion of a vessel. Hydrodynamics of an ideal fluid is described in detail by Newman [12], Mei [11], and Faltinsen [8]. Viscous force such as drag force is treated in detail by Hoerner [9] and Sarpkaya and Isaacson [14]. General hydrodynamics for offshore structures is explained by Chakrabarti [4], and Clauss, Lehman, and Oestergaard [5].
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