Temporal Model for Ship Twin-Propeller Jet Induced Sandbed Scour

Abstract

This research paper proposes the use of empirical equations to estimate the temporal maximum scour that is induced by twin-propeller ( ε t w i n = Ω t [ l n ( t ) ] Γ t ) when acting over non-cohesive bed materials. A purpose built experimental apparatus is used to obtain the measurement data required for the calculation of the empirical constants. The output from rigorous experimental investigations demonstrates that the maximum scour depth produced from the operation of twin-propeller ( ε t w i n ), within the confines of a harbour basin, varies as a logarithmic function of time. A dimensional analysis of the standard single propeller configuration is used as the foundation upon which the scour equation is postulated. This is extended to include the influence of the operating distance between the twin-propeller configurations for the first time. The division of scours by twin-propeller and single-propeller ( ε twin / ε m ) enables the establishment of mathematical relation to calculate C1, C2, A, and B. The constants are C 1 = 366.11, C 2 = 0.3376, A = 0.859, and B = 0.1571. The proposed scour equation is more reliable within the time zone up to two hours based on the experimental data.