Highly accurate and precise heave decay tests on a sphere with a diameter of 300 mm
were completed in a meticulously designed test setup in the wave basin in the Ocean
and Coastal
Engineering Laboratory at Aalborg University, Denmark. The tests were dedicated to
providing
a rigorous benchmark dataset for numerical model validation. The sphere was ballasted
to half
submergence, thereby floating with the waterline at the equator when at rest in calm
water. Heave
decay tests were conducted, wherein the sphere was held stationary and dropped from
three drop
heights: a small drop height, which can be considered a linear case, a moderately
nonlinear case,
and a highly nonlinear case with a drop height from a position where the whole sphere
was initially
above the water. The precision of the heave decay time series was calculated from
random and
systematic standard uncertainties. At a 95% confidence level, uncertainties were found
to be very
low—on average only about 0.3% of the respective drop heights. Physical parameters
of the test
setup and associated uncertainties were quantified. A test case was formulated that
closely represents
the physical tests, enabling the reader to do his/her own numerical tests. The paper
includes a
comparison of the physical test results to the results from several independent numerical
models
based on linear potential flow, fully nonlinear potential flow, and the Reynolds-averaged
Navier–
Stokes (RANS) equations. A high correlation between physical and numerical test results
is shown.
The physical test results are very suitable for numerical model validation.
