Systematic studies for recording squat and trim together with ship-induced pressure and wave systems when passing through channels in confined shallow water

Author: K. Uliczka

Boundary conditions

The studies into the dynamic behaviour of very large Post-Panamax container ships when passing through waterways of confined width and depth were conducted in BAW-DH’s shallow water basin (length approx. 100 m, width approx. 35 m, max. water depth 0.7 m) at 1:40 scale in accordance with Froude’s model laws.
The dimensions and investigated parameters for the model ships used were as follows:

Designation	Length	Beam	Draught	UKCR*	cB-value**	SR+	Weight trim	KG++
-	m	m	m	m	-	-	-	m
JUMBO	320	40	14,5	1-2	0,740	6,29	Hard	11,8
MEGA-JUMBO	360	55	15,5	1-1,5-2	0,677	6,10	Hard	10,2

*UKCR: under-keel-clearance, **cB: block coefficient , +SR: slenderness ratio, ++KG: centre of gravity above keel The Froude numbers amounted to 0,27 < Fr_h < 0,68. The Reynolds numbers were determined to be 3,1 · 10⁶ < Re < 6,2 · 10⁷ (factor 10 > Re_KRIT,erf). Fulfilling the geometric and dynamic similarity conditions ensured that the studies would deliver valid forecasts. The waterway cross-sections and (partial-)cross-sectional ratios are presented in Figure 1 taking the MEGA-JUMBO as an example:

• Trapezoidal profile, central course, cross-sectional ratios n = 25, 20, 15, 10.
• Trapezoidal profile, off-centre course, partial cross-sectional ratios nT = 10/5, 20/10, 25/10.
• Combined profile, off-centre course, partial-cross-sectional ratios nT = 25/10, 20/10, 10/5.

Comments:
Cross-sectional ratio n = A / A_S
where: A wetted area of waterway
A_S submerged midship cross-section
Partial-cross-sectional ratio n_T = A_T / 0,5 A_S
where: A_T area of wetted partial-cross-section (from course to bank)

As well as measuring ship dynamics (squat, trim), the speed-dependent changes in the water level in a transverse profile were also assessed and analysed. Selected results are presented and evaluated below.