A pseudo-analytical model for CSD spillage due to rotational velocity-induced flow

Abstract

This paper proposes a classification of the concurrent sources of Cutter Suction Dredger (CSD) spillage as well as a pseudo-analytical model for a-priori computation of spillage rates due to high rotational velocity-induced flow. As of yet, in literature, no analytical models exist that describe spillage due to centrifugal advection. Based on work performed by Miedema (2017) and Nieuwboer (2018), a preliminarymodel is set up that includes most relevant cutting variables, or a simplification thereof. However, in this preliminary model, the axial pump effect described in Den Burger is not explicitly accounted for and the pressures exerted on the cutterhead contour are heavily simplified. An adaptation of a governing dimensionless velocity ratio proposed by Steinbusch et al. (1999) and Dekker et al. (2003) is used for model calibration using experimental data for sand from Miltenburg (1983) and rock from Den Burger (2003). Model parameters were identified for which sand spillage can be estimated within a 5 percentage point bandwidth of the experimental data. Moreover, the shape of the model plot appears to resemble that of the data for sand accurately, i.e. the model behaves as expected. The preliminary model is not capable of accurately estimating rock spillage rates over a wide range of mixture velocities. This inaccuracy may be ascribed to the concurrence of other spillage sources. The preliminary proposed model may not entirely capture the centrifugal effect of the cutterhead for larger grain sizes. Recommendations are given for further research.