Cooperative Resistance Tests with Geosim Models of a High-Speed Semi-Displacement Craft

Tanaka, Hiraku; Nakato, Michio; Nakatake, Kuniharu; Ueda, Takayasu; Araki, Shigeru

doi:10.2534/jjasnaoe1968.1991.55

Cited by 9 publications

(1 citation statement)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In free to trim and heave tests, such as those by Tanaka et al (1991), small model scale can affect the running trim angle resulting from the difference in pitching moment caused by changes in friction coefficient. This change in trim has a substantial impact on all other planing parameters in free to trim tests, not present in fixed trim tests.…”

Section: Scale Effectsmentioning

confidence: 99%

Planing in Shallow Water at Critical Speed

Morabito¹

2013

Journal of Ship Research

View full text Add to dashboard Cite

This article summarizes experiments to determine the effect of shallow water on flatbottomed prismatic hulls towed fixed in heave and trim over a wide range of speed regimes. The experimental design allowed for the separate measurement of pressure forces normal to the bottom and viscous forces tangential to the bottom. The experiments showed that below a depth Froude number of unity (subcritical speeds), shallow water resulted in a reduction in pressure forces on the bottom of the hull. Around a depth Froude number of unity (critical speed), a solitary wave formed at the model, increasing the wetted length and also increasing the bottom pressure forces, which became unsteady. Above a depth Froude number of unity (supercritical speeds), the pressure forces on the bottom of the hull were greater in shallow water than in deep water. Observations of the inception of transom ventilation showed that full ventilation occurred at lower Froude numbers in shallow water and that trim has a strong effect on transom ventilation at all water depths. To assist in explaining these effects, each of the forces acting on a flat-bottomed hull are discussed and it is shown how they vary with speed and water depth. The observed trends from these fixed model tests are in qualitative agreement with experiments with free to trim and heave models as well as two-dimensional theories of planing in shallow water.Early work on shallow water effects such as Schlichting (1934), Landweber (1939, and Lackenby (1963) focused on estimating the speed loss of seagoing displacement ships during sea trials in shallow or restricted waters or estimating towing tank blockage corrections. It has been found that as the depth Froude number approaches unity (critical speed), there is an increase in resistance, which often results in speed loss for ships.Supercritical behavior of displacement and semidisplacement hulls has been studied more recently. Kirsch (1966) computed the theoretical wave resistance for a simplified ship form in shallow and restricted channels using Sretenskii's (1937) method. Calculations were at subcritical and supercritical speeds, showing that resistance decreased in shallow water at supercritical speeds. Millward (1983) and Millward and Bevan (1986) extended Kirsch's calculations and found that the method correlated well with resistance measurements from towing tests of semidisplacement Manuscript received as SNAME headquarters

show abstract

Section: Scale Effectsmentioning

confidence: 99%