Trans RINA, Vol 161, Part A4, Intl J Maritime Eng, Oct-Dec 2019


where (1+k) is the form factor by Prohaska, CFS is the frictional resistance coefficient of the ship according to the ITTC-1957 model-ship correlation line, ΔCF is the roughness allowance, CA is the correction allowance, CAAS is the air resistance coefficient, CR is the residual resistance coefficient that is considered as the same value for both the model and full scale ship (ITTC, 2011a). CR is calculated as follows (ITTC, 2011c):


= − (1 + ) (9)


Here, CTM can be expressed in non-dimensional form by resistance measured of model,


= 0.5ρS


2 (10)


CFM is calculated with Re number by ITTC-1957 line as follow,


= 0.075 (log − 2)2


(11)


The form factor can be calculated by (ITTC, 2011c). In this study, only two main resistance components, CF and CR have been considered. Detailed information about other coefficients and calculations can be found at ITTC, (2011b, 2011a).


3. GEOMETRY AND TEST CASES


In this study, a modern container ship (KCS) has been selected for the CFD analysis. KCS has a bulbous bow designed by Korea Research Institute of Ships and Ocean Engineering (Van et al., 1998; Kimet al., 2001). KCS hull is widely used for validation & verification of CFD applications (Carrica et al., 2010; Simonsen et al., 2013; Gaggero et al., 2017). The main dimensions of the model families of KCS used in this study, have been given in Table 1. The general views of the KCS model have been shown for Model 1 in Figure 1.


These scale ratios used in this study have been selected since they are frequently used in the literature. The experiments of Model 1 were also carried out in Ata Nutku Ship Model Testing Laboratory of Istanbul Technical University (Delen and Bal, 2015a). The model tests of Model 2 and Model 3 (other scales) were performed in FORCE and NMRI towing tanks, respectively. Model 2 and 3 are also one of the benchmark cases (cases 2.1 & 2.10) in Tokyo 2015 Workshop on CFD in ship hydrodynamics. The CFD analyses of KCS hulls with rudder were carried out in calm water at design Fr number as in the experimental conditions.


Figure 1: Views of KCS hull (Model 1). 4.


EXPERIMENTAL SETUP


KCS model was produced in accordance with the ITTC (2011c) Recommendation Procedures and Guidelines at 60.75 scale ratio in the laboratory workshop in 2014. Resistance tests of KCS hull were conducted in the towing tank of Ata Nutku Ship Model Testing Laboratory. The towing tank has a length of 160 m, a width of 6 m, a water depth of 3.5 m. The maximum speed of the towing carriage is 5.5 m/s. Uncertainty analysis of resistance tests had also been estimated for this model with ITTC, (2002) and ITTC, (2014). For this study, the experiments have been extended to include the trim values of Model 1 into results. The resistance, trim and velocity signals have been measured simultaneously by taking into account the ITTC procedures (ITTC, 2002a, 2011a, 2011c). Tested model had a certain freedom of movement (sinkage and trim) during tests. The measurement data have been processed considering the same time domain. The expanded uncertainty value of total resistance coefficient of KCS


A-470 ©2019: The Royal Institution of Naval Architects


Table 1: Main particulars of KCS. Parameter Model 1 Model 2 Model 3


ʎ


LPP (m) B (m) T (m)


S (m2)


(w/rudder) ∇ (m3)


CB


LCB (%LPP), fwd+


V (m/s) Fr Re


1.584 2.006 0.26 5.26E+06 1.07E+07 1.40E+07 2.49E+09


60.75 3.786 0.530 0.178


2.585 0.232


37.89 6.070 0.850 0.285


6.644 0.956


0.643 -1.48


2.196 12.346 31.6


7.278 1.019 0.342


9.553 1.649


Full scale


1.0


230.0 32.2 10.8


9539 52030


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