Estimation of Shallow Water Effects Using Empirical and Numerical Methods for Inland Vessels

Abstract

Due to the increased demand for transportation of cargoes through waterways, there is a need for more and efficient inland vessels. The Inland Waterways Authority of India (IWAI) has planned initiatives to augment the inland waterways sector through strategic development, complementing one activity with others to ensure efficient and effective movement of goods within the country for in-bound and out-bound destinations. A key element of this plan will be the design of specific vessels that are well adapted to the navigation on the National Waterway NW-1. DST has supported design of inland vessels for National Waterway-1 as a part of Jal Marg Vikas Project. The vessel design is mostly depending on the features of channel and payload. The design needs to be optimized such that the entire voyage becomes economical. Such designing of a low-draught vessel for inland waterways is always critical due to the complexities involved in its powering calculations because of shallow depth of the channel. These situations demand a study for the effect of the bottom surface on powering of the vessel. In this study, a hull proposed by Inland Water Authority of India (IWAI) for National Waterway-1 is taken as the reference hull, and resistance study has been done for both deep water and shallow water cases. Also, different standard empirical methods are used to estimate the resistance. Since the Computational Fluid Dynamics (CFD) tools present a better alternative to experimental studies, we explored the application of such tools for such investigations and validated the results with empirical calculations. Upon validation of results, the best empirical method and its limitations are proposed for future studies. The CFD analysis is done by using SHIPFLOW where both potential solver and RANS solvers are integrated in an optimized way so that computation becomes faster compared to other CFD tools. In all the simulations, the vessel is restrained from trim and sinking. For each hull, the squatting effect due to shallow water is also investigated. The simulations are run for low Froude no: conditions where frictional resistance dominates the wave resistance component in deep water conditions.