Experimental Measurements of the Minor Loss due to Fixed Screens at Suction Entrance for a Cutterhead Model Dredge
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The cutter suction dredge ranks among all types of dredges as one of the most widely used due to its capability to tackle almost any kind of soil for many different environments, depending on its size and power. Dredges of this type are often employed in locations where the seabed has debris and unexploded ordinances, which should be blocked from entering the suction line given their inherent system damage potential. Dredgers are required to install a screen over the suction inlet to keep not only these undesired particles, but also small animals and larger rocks from joining the produced slurry and reaching the pumps. However, with the installation of such fixtures the operator must account for minor losses, which must be taken into consideration in the overall calculations for the design of the system. The goal of this research was to evaluate the behavior of a designed fixed screen with 55% of its area cut out, and evaluate experimentally the minor loss coefficient across different values of flow rates, ladder arm swing speeds and cutterhead rotational speeds. Intending to cover all combinations of operating settings, a total of 72 tests for three different screen configurations with different opening areas were run and provided data that were further analyzed and compared to previous experimental research. Preliminary results showed only a weak relationship between the specific gravity of the slurry and increasing values of the previously mentioned dredging parameters, which raised the hypothesis of the potential effect of the magnitude of the operating parameters on the overall results. This research also presented results that confirmed the effect of the high cutterhead rotational speed over the conducted set of tests and its influence over the prediction of minor loss coefficient (k). The results from the proposed screen showed close correspondence with formerly developed prediction equations for the range of velocities employed and served as inputs for the computation of a new exponential model whose curve fit comprised all the data found in the literature for the phenomena under investigation. Moreover, the author found that the constants present in the prediction equation are actually functions of the cutter rotational speed and their study is recommended for future experiments across a wider range of fixed screen opening areas and operating parameters.
minor loss coefficient
cutterhead suction dredge
cutterhead model dredge
Texas A&M University
de Oliveira Junior, Paulo Tadeu (2016). Experimental Measurements of the Minor Loss due to Fixed Screens at Suction Entrance for a Cutterhead Model Dredge. Master's thesis, Texas A & M University. Available electronically from
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