Does the towing tank temperature affect model-ship extrapolation?

Answer to the question, “Does the towing tank water temperature affect the model-ship extrapolation?” was sought in this study. The answer could indicate whether warm or cold water leads to a more favourable assessment of hull resistance. Specifically, we investigated the potential temperature-sensitivity of the towing tank during the model-ship extrapolation process. To make a long story short, colder water temperatures result in a lower evaluated ship-scale resistance. This temperature-sensitivity arises from two main factors. One, the imperfection of the ITTC 1957 correlation line. Two, the disregard for changes in the form factor with temperature (i.e. Reynolds number).Model-scale Computational Fluid Dynamics (CFD) simulations were conducted for two ship models, KCS and KVLCC2, under different water temperatures. The study evaluates how well the ITTC friction line accounts for temperature variations and their effect on resistance extrapolation. Using the ITTC 1978 method, we determined that water temperature significantly influences model-ship extrapolation, revealing limitations in the ITTC 1957 friction curve, which fails to capture the full effect of temperature on skin friction. Additionally, we analysed the temperature-sensitivity of various friction curves, including the Kármán–Schoenherr (ATTC) formula, Grigson formula, Katsui equation, and an "imaginary" friction curve designed to match the CFD results