## 4 Case study and Results
Figure 7: Ships advance on circular trajectory in deep and shallow waters (depending on _T/H_), received by calculation (lines), real ship experiments (G class container ship, container ship 9000 TEU, bulk ship 80,000 t) and calibrated simulator (G class container ship, container ship 9000 TEU, bulk ship 80,000 t). The compliance between the results of the calculations and the experiments is quite high (the difference does not exceed 10 percent (Table 1)) (Figure 8), and therefore it can be concluded that the methodology presented in Section 3 for the calculation of the ship's engine power increasing during sailing at low depths can be used for practical purposes for the assessment of the performance of ships when sailing through channels and other similar locations with low depths. The port of Klaipeda was chosen for the case analysis. The passage of a standard LNG tanker from the entrance channel to the southern turning basin of the port was analyzed (Figure 9). \begin{table}
\begin{tabular}{l c c c c} \hline \hline \multirow{2}{*}{**Ship**} & \multirow{2}{*}{**T/IH**} & \multirow{2}{*}{**Calculated Advance, m**} & \multicolumn{2}{c}{**Difference Advance**} & \multirow{2}{*}{**Percentages from**} \\  & & & **between Experimental** & \\  & & & **and Calculation, m** & \\ \hline G class Container & 0.76 & 1430 & 30 & 2.1 \\ G class Container & 0.61 & 1350 & 48 & 3.6 \\ G class Container & 0.55 & 1330 & 32 & 2.4 \\ G class Container & 0.37 & 1260 & 22 & 1.7 \\ G class Container & 0.14 & 1120 & 18 & 1.6 \\ Container 9000 TEU & 0.73 & 1050 & 20 & 1.9 \\ Container 9000 TEU & 0.62 & 1030 & 27 & 2.6 \\ Container 9000 TEU & 0.47 & 1005 & 31 & 3.1 \\ Container 9000 TEU & 0.13 & 850 & 41 & 4.8 \\ Bulk 80,000 t & 0.83 & 790 & 22 & 2.8 \\ Bulk 80,000 t & 0.61 & 740 & 30 & 4.1 \\ Bulk 80,000 t & 0.31 & 680 & 28 & 4.1 \\ Bulk 8000 t & 0.06 & 603 & 18 & 3.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The difference (accuracy) between the results of calculation and experiments (obtained on real ships and with the help of a calibrated simulator) of ships’ advance in circulation in meters and percentages from experimental results. Figure 8: Ship’s main engine power coefficient depending on ship’s draft and depth ratio (_T_/_H_) and ship’s overall hull fullness factor (DELTA) (calculation and experimental results). The main engine power, fuel consumption and emissions of the ships were calculated according to the methodology presented in Section 3. The SimFlex Navigator simulator was used to change the clearance under the hull. Experiments were carried out on real ships (LNG standard tankers, length approx. 290 m, beam approx. 49 m, draft approx. 12 m, overall fullness coefficient approx. 0.75). The speeds adopted and used in the calculations, simulator and actual LNG carriers for the majority of the passage (up to the turning basin) were between 7 and 8 knots. The calibration of the simulator was carried out by comparing the results of a real ship and a ship in the simulator. The simulator calibration was produced by calibration coefficients for the ship's main engine power, fuel consumption and the ship's speed at high and low depths. Following the simulator calibration, experiments were carried out on the simulator at various depths and speeds in the range from 6 to 10 knots and at characteristic depths in harbor approaches and ports, i.e., a _T/H_ between 0.6 and 0.92. The main engine power, speed and fuel consumption of the LNG standard tanker in the approach and internal navigational channels of the port of Klaipeda, obtained in a calibrated simulator, are shown in Figure 10.  
The variation of the main engine power and fuel consumption factors for the LNG standard tanker sailing at a constant speed as a function of the ship's  
Figure 10: The LNG standard tanker engine power, ship’s speed and fuel consumption obtained in a calibrated simulator. Figure 9: LNG standard tanker sailing trajectory in Klaipeda port.