Schlichting Shallow-Water Correction

Speed reduction for a given delivered power when a ship enters shallow water - Schlichting's 1934 correction.

ResistanceShallow water

Ship speed (deep water)knWater depth hmDraft Tm

Shallow-water speed (same power): 6.83kn

Speed loss: 51.2%

Changing the inputs requires JavaScript. The calculator above shows its default inputs and result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

\frac{V_\text{shallow}}{V_\text{deep}} \approx \tanh\sqrt{h/8T} \quad (h/T < 8)

Symbol	Meaning	Unit
$V_\text{deep}$	Deep-water speed at rated power	kn
$V_\text{shallow}$	Shallow-water speed at same power	kn
$h$	Water depth	m
$T$	Draft	m

Source: Schlichting (1934); ITTC 7.5-04-01 Shallow Water

In short

Speed reduction for a given delivered power when a ship enters shallow water - Schlichting's 1934 correction.

Learn the theory Ship resistance and powering