Some Experimental Results with Ship Model Acceleration Waves

The wave resistance of a ship moving at a constant speed can be calculated using information obtained from its wave pattern. One of the basic assumptions in wave survey methods is t1he existence of a time-independent model speed. In towing tanks initial acceleration is unavoidable. Wehausen (1964) showed that the effect of initial acceleration on wave resistance has a decaying and oscillating character. Çalişal (1977) gave the general form of the initial acceleration potential and showed the existence of a two-dimensional wave of the formζT=AcTsin[14k0(x−cT)+ϕ(t)]+0(cT)−2(1)To study the validity of the theoretical results, some experiments were performed. The variation of the measured spectra and the frequencies within the recorded total resistance pitching moment are of interest. Results indicate that models should travel a distance proportional to the square of the Froude number before wave data collection can begin, that the predicted encounter frequency exists in the recorded total resistance and pitching moment signals, and that special effort is required to avoid initial acceleration waves due to wall effects.