Showing papers by "K. Murali published in 2010"

Rans Predictions of Free Surface Effects on Axisymmetric Underwater Body

Abstract: The aim of the current investigation is an assessment of the influence of free surface effects on hydrodynamic coefficients of an axisymmetric underwater body using Reynolds averaged Navier-Stokes (RANS) solver. This paper mainly focuses on the capabilities of turbulence models (two high-Re models, k-e Re-Normalised Group (RNG) and k-e Realizable and one low-Re model, k-e Abe-Kondoh-Nagano (AKN) together with volume of fluid (VOF) method for hydrodynamic investigation of an axisymmetric underwater body (Afterbody1) near the free surface. The current numerical investigations were carried out to simulate measured hydrodynamic coefficients for several experimental parameters, including velocity variations from 0.4 m/s (Reynolds number Rev = 2.12x 105) to m/s (Reynolds number Rev = 7.42 x 105), depth of submergence from 0.75D to 4.0D, and angle of attack 0° to 15° on a vertical plane for a model scale of 1:2. Numerical simulations were conducted at a grid density of 0.46 million cells based on grid in...

Estimation of hull-propeller interaction of a self-propelling model hull using a RANSE solver

Abstract: Viscous flow around the self-propelled hull was investigated at model scale with a RANSE solver using k-ϵ turbulence model by coupling the flow around the hull model with the flow generated by the rotating propeller. Hence, the challenges involved in the coupling of flow past ship hull with propeller flow of lower-order scale have been brought out and addressed here. Propeller rotation is accounted for by mesh motion; the solution domain is represented by a rotating cylindrical domain encompassing the propeller and a fixed rectangular domain around the hull for the remaining part of the solution domain; both these domains are interfaced by sliding interfaces. Comparisons are made between the simulated results and corresponding experimental results for hull resistance, propeller thrust and propeller RPM. It is shown that the flow field in the self-propelling condition is well reproduced in the simulation, and the estimated thrust deduction factor and RPM agree well with the measured ones. Among the various...

Identification of Suitable Grid Size for Accurate Computation of Run-up Height

Abstract: A numerical investigation has been carried out to obtain a non-dimensional grid size (grid size/ tsunami base width) for the near shore discretisation of computational domains for long wave modelling. A 1D domain has been considered in which, the flow has been solved by 1D shallow water equations with vertically integrated flow variables. The sensitivity study of the grid size was carried out in the 1D channel with an open boundary at one end and shelf boundary at the other end. The grid size was varied from 10 m to 1000 m and its effect on the computation of the tsunami run-up along the shoreline has been investigated. The non-dimensional grid size for the computation of run-up was optimised by comparing the non-dimensional run-up (tsunami run-up/initial tsunami height) and a threshold value of 5.0e-4 was obtained. Further, the study was extended to real scenario by adopting various grids for the shelf region of northern Tamil Nadu coast, south east coast of India in 2D and a suitable grid size was obtained.