Techniques for Ship Frictional Resistance Measurements

摘要

Total ship resistance consists of two components, frictional resistance and pressure (residual) resistance. Frictional resistance can be obtained by the integration of the measured shear stress distribution over the hull, and pressure resistance can be obtained from the integration of the measured pressure distribution on the hull. Pressure resistance is further divided into a wave component and a viscous component (form drag). Wave resistance can be measured by a method which takes a longitudinal or a transverse cut of the wave pattern. The expressions for computing the frictional and the pressure resistance from the measured shear stress and normal pressure distributions are derived. Experimental techniques for measuring the magnitude as well as the direction of shear stress were explored in detail by hot-film shear probes. These probes are recommended for measuring the shear stress distribution on small models for measuring the shear stress distribution on small models tested in towing tanks; hot-film shear probes with ambient temperature compensation and directional Preston probes are recommended for use in tests of full-scale ships and large-scale models. (Author)