• Version
• 108 Downloads
• 1.11 MB File Size
• 1 File Count
• January 31, 2017 Create Date
• January 31, 2017 Last Updated

National Advisory Committee for Aeronautics, Technical Notes - Impact-Loads Investigation of Chine-Immersed Model Having a Circular-Arc Transverse Shape

An investigation of hydrodynamic impact loads on chine-immersed
bodies of heavy beam loading at the Langley impact basin has been
expanded to include transversely curved models in addition to models of
prismatic shape. This paper presents the results from tests of a chine-
immersed model having a circular—arc cross section with a radius of
l beam. The results were obtained from fixed-trim impacts made in smooth
water over a wide range of trim and initial flightapath angles. Most of
the impacts were made at a beam—loading coefficient of 18.59 with a few
impacts at beam-loading coefficients of 27.59 and 56.57.

The data are presented in tables, and the coefficients of loads and
motion are presented in figures as a function of trim and initial flight—
path angles. The circular-arc model experienced loads greater than loads
predicted by theory for this configuration by about 10 percent. These
loads are as much as 12 percent less than the loads measured under similar
conditions for a model with concave-convex cross section with a similar
effective angle of dead rise.

Investigations of hydrodynamic impact loads on chine—immersed bodies
at the Langley impact basin have dealt largely with models of flat and
V-bottom transverse shapes such as reported in references 1 and 2. This
study was expanded in reference 5 to a model with a concave-convex trans-
verse shape (a ccnstant-force-type bottom). The concave—convex model
yielded maximum loads comparable to loads predicted by theory for a
V—bottom.of the same effective dead—rise angle and indicated that such
shape deviations from the conventional V-bottom have little effect on the
maximum load. Further studies of the effect of transverse shape on hydro-
dynamic impact loads, with greater deviations from the V-configuration,
were made on a model of circular-arc cross section having a radius of
l beam.

This bottom shape was installed on a model having a straight Keel,
and a series of fixed—trim impacts in smooth.water was made at the
Langley impact basin. Most of these impacts were made at a beam-loading
coefficient of 18.59 and covered a range of trim and initial flight-path
angles; however, a few impacts were made at a trim angle of 8° with beam—
loading coefficients of 27.59 and 56.57. The purpose of this investiga-
tion was to obtain loads and moment data on a chine-immersed model having
a circular-arc transverse shape.