The turbulent jet produced by a ship propeller may impact the seabed even for distances of the order of tens of times the diameter of the propeller itself. The result is the formation of a scour hole close to the propeller and a deposition mound. The present work aims at investigating, for the first time, the scaling behavior of the high-order structure functions for this turbulent jet, by discussing the experimental results in light of monofractal or multifractal models. This latter would explain the possible existence of intermittency. To this end, an experimental test was performed in a laboratory flume in still water condition, simulating the case of a ship in a harbour basin. The propulsion system was constituted by an electric motor turning a propeller (8.2 cm in diameter) with four blades. The flow field induced by the propeller rotation was measured with an Acoustic Doppler Velocimeter (ADV). Specifically, the longitudinal structure functions were studied in this work using Taylor’s hypothesis.

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The Scaling Behavior of High-Order Structure Functions for a Turbulent Jet Induced by a Rotating Propeller

  • Nadia Penna,
  • Giuseppe Curulli,
  • Roberto Gaudio

摘要

The turbulent jet produced by a ship propeller may impact the seabed even for distances of the order of tens of times the diameter of the propeller itself. The result is the formation of a scour hole close to the propeller and a deposition mound. The present work aims at investigating, for the first time, the scaling behavior of the high-order structure functions for this turbulent jet, by discussing the experimental results in light of monofractal or multifractal models. This latter would explain the possible existence of intermittency. To this end, an experimental test was performed in a laboratory flume in still water condition, simulating the case of a ship in a harbour basin. The propulsion system was constituted by an electric motor turning a propeller (8.2 cm in diameter) with four blades. The flow field induced by the propeller rotation was measured with an Acoustic Doppler Velocimeter (ADV). Specifically, the longitudinal structure functions were studied in this work using Taylor’s hypothesis.