EM 1110-2-1100 (Part II)
30 Apr 02
EXAMPLE PROBLEM II-1-6
Applicable wave theory for waves in (a) and (b). Which of these waves is a long wave?
(a). d = 15 m, H = 12.2 m, T = 12 sec; (b). d = 150 m, H = 30 m, T = 16 sec.
(a) Calculate dimensionless parameters necessary for using Figure II-1-20. These are
gd . 12
UR . 55
From Figure II-1-20, the applicable theory is cnoidal.
(b) In a similar fashion, compute
gd . 40
UR . 1.5
With these values, Figure II-1-20 indicates the applicable theory is Stokes third- or fifth-order. It is noted
that the linear theory is also applicable.
Based on the values of Ursell parameter, neither wave (a) or (b) is a true long wave. Wave (a) may be
considered a long wave in comparison to wave (b).
Water Wave Mechanics