180
P. Liu
Fig. 3.6 H Darcy (1803—1858, French engineer)
3.2 Liquid Motion
3.2.1 Ideal Liquid Motion
A liquid that ignores viscosity is called an ideal liquid. According to Prandtl’s
boundary layer theory, in the region outside the boundary layer, the viscous
force cannot be considered, so the motion law of ideal liquid can still be
applied under specific conditions. Before Prandtl, there had been a lot of
research in this field. The compressibility of liquid is very small; only in cases
such as water hammer, sound wave in water, shock wave propagation, etc.,
the compressibility of liquid should be considered.
3.2.2 Viscous Liquid Motion
Some liquids, such as lubricating oil, are very viscous and must be taken
into account when analyzing their flow states (see Stokes flow). In addition,
the viscosity of the liquid must be considered in the analysis of the friction
resistance of the ship, the interference between the boundary layer and the
wave, and the wake of the ship and the submerged body. The viscosity of
P. Liu
Fig. 3.6 H Darcy (1803—1858, French engineer)
3.2 Liquid Motion
3.2.1 Ideal Liquid Motion
A liquid that ignores viscosity is called an ideal liquid. According to Prandtl’s
boundary layer theory, in the region outside the boundary layer, the viscous
force cannot be considered, so the motion law of ideal liquid can still be
applied under specific conditions. Before Prandtl, there had been a lot of
research in this field. The compressibility of liquid is very small; only in cases
such as water hammer, sound wave in water, shock wave propagation, etc.,
the compressibility of liquid should be considered.
3.2.2 Viscous Liquid Motion
Some liquids, such as lubricating oil, are very viscous and must be taken
into account when analyzing their flow states (see Stokes flow). In addition,
the viscosity of the liquid must be considered in the analysis of the friction
resistance of the ship, the interference between the boundary layer and the
wave, and the wake of the ship and the submerged body. The viscosity of