Wave Related Defination

Significant wave height, HS
The average height (trough to crest) of the highest one-third waves in the indicated time period, also denoted H1/3.

Peak Period, TP
It is the inverse of the frequency at which a wave energy spectrum has its maximum value.

Zero-up-crossing period, TZ
It is the average time interval between two successive up-crossing of the mean sea level.

Keulegan-Carpenter number, KC
KC=VT/D
Where,

• V = flow velocity; 
• T = period;
• D = pipeline diameter.

Keulegan-Carpenter number also known as Period Number. It generally describes two things:

1. Relative importance of drag force over inertia force (Small KC number, inertia dominates; large KC number, the drag force is important);
2. Wave ellipse size relative to the pipeline diameter (Small KC number, current dominated; large KC number, the wave is current-like)