The densimetric Froude number, F0, which depends on the propeller rotational speed, n, and on the median diameter of bed sediments, d50, is the main parameter considered by researchers for analysing the propellerinduced scouring process. Common literature equations for evaluating the three-dimensional (3D) geometric characteristics of the scour hole and deposition mound are functions of F0. In this paper, the agreements among the data and these literature equations are critically discussed, demonstrating that the use of other two dimensionless parameters (the propeller Froude number, F0p, and d50/Dp where Dp is the propeller diameter), which are separately dependent on n and d50, returns more satisfying results than using F0 solely. Also, the influence of the water depth, h, on the scour hole and the deposition mound is here analysed. Researchers commonly neglected the effects of h, because the ratio between it and Dp was large enough. This is reasonably true when h/Dp is considerably high, but no clear cut-off value was found in the literature. For the first time, by investigating a larger range of h, the present study underlines that the effects of h on the scour hole and the deposition mound are negligible for h/Dp ≥ 2.44.

Improved formulation for the geometric characteristics of the scour hole and deposition mound caused by a rotating propeller jet on a mobile bed

CURULLI G.
;
PENNA N.;GAUDIO R.
2023-01-01

Abstract

The densimetric Froude number, F0, which depends on the propeller rotational speed, n, and on the median diameter of bed sediments, d50, is the main parameter considered by researchers for analysing the propellerinduced scouring process. Common literature equations for evaluating the three-dimensional (3D) geometric characteristics of the scour hole and deposition mound are functions of F0. In this paper, the agreements among the data and these literature equations are critically discussed, demonstrating that the use of other two dimensionless parameters (the propeller Froude number, F0p, and d50/Dp where Dp is the propeller diameter), which are separately dependent on n and d50, returns more satisfying results than using F0 solely. Also, the influence of the water depth, h, on the scour hole and the deposition mound is here analysed. Researchers commonly neglected the effects of h, because the ratio between it and Dp was large enough. This is reasonably true when h/Dp is considerably high, but no clear cut-off value was found in the literature. For the first time, by investigating a larger range of h, the present study underlines that the effects of h on the scour hole and the deposition mound are negligible for h/Dp ≥ 2.44.
Propeller scour; Unconfined scouring process; Water draft effects; Eroded area; Eroded sediment volume
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11770/340616
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