Numerical Simulation of Full-Scale Ship Self-Propulsion for Japan Bulk Carrier

The self-propulsion simulations of JBC (Japan Bulk Carrier) were performed in model and full scale with two approach: one is the body force method using steady blade element theory (lift lines theory) and infinite blade propeller, the other is 3-D discretized propeller method. All simulations were investigated using an in-house CFD code which is based on the finite difference method to discretize the governing equations. A dynamic overset technique was used and any revolutions of the propeller can be achieved in the simulation. In order to obtain the self-propulsion point, a PI speed controller was utilized to adjust the rate of revolutions of the propeller. To obtain self-propulsion factors, resistance and open water tests are also computed. Thrust identity method was used to obtain wake fraction. The full scale total resistance coefficient was obtained according two extrapolation methods: the first is the ITTC 1978 recommended procedure, while the second is the extrapolation method based on Grigson friction line. Wake fraction was revised following ITTC recommended procedures in full scale. All the results of the simulation have a reasonable agreement with experimental results. The computational results presented in this paper also provide evidence to the full scale self-propulsion prediction ability of the in-house code.

The friction line between “lying” and “truth”, Oedipal conflict, and traumatic speaking and silence in Pat Barker’s Regeneration

The present article analyses the first part of Pat Barker’s trilogy Regeneration (1991-1995), of the same title. It is set in the First World War and turns around the encounter between psychiatrist E. M. Rivers and War poet Siegfried Sassoon when the latter suffers from shell shock and publishes a complaint against the war politics of the British government. From the analysis of Sassoon’s Declaration, my main contention is that the novel addresses the liminal territory between “truth” and “lying” when representing and memorialising a traumatic event like WWI. In the second part, I delve into the poetics of psychoanalysis and (poetic) language as the narratives Barker uses to articulate the rapport between generations: fathers furthering a war in which their sons are involved. With this in mind, the paper analyses their oedipal conflict, as well as that between healer (Rivers) and trauma victim (Sassoon) both at a personal and national level.

Comparative modeling of hull form resistance for three ocean going vessels using methodical series

This paper presents a comparative estimation of the hull form resistance for Cargo ship, Ocean-going Tug and Container ship. The research study evaluates the influences of various ship hull parameters in relations to the vessel speeds and level of turbulence (Reynolds number). The modeling was done using MATLAB software and the model test technique based on the ITTC, ATTC, Granville and Hughes friction line application. The result shows that the hull form resistances follow the same trend in the ITTC, ATTC and Granville models, while the Hughes model gave a different trend with other techniques. It further revealed that as the speed increases by 10knots, the frictional resistance coefficients decrease by 11.86% for the ITTC & Granville models, and 12.03% for the Hughes model. For Ocean-going Tug and Container Ship, the frictional resistance coefficient decrease by 12.31% for the ITTC & Granville models, and 12.14% for the Hughes model. The Reynolds number increase by 62.52% for every 10knots increase in the speed of the Cargo ship and 62.23% for every 10knots increase in the speed of the Ocean going tug and Containership. At various experimental speeds, the results showed that for every 1 knots increase in the speed of the Containership, the effective power developed increases by 9.45%. This provides a technical and analytical guide on hull form resistance trend for engineers and ship operators.

Scaling of Resistance From Surface-Effect Ship Model Tests

In the case of conventional (displacement) hulls, model testing is based on the assumption (with or without certain refinements) that the total resistance can be expressed as:RT=RF+RR(1)where Rt is measured in the towing tank, and the frictional resistance, Rf, can be accurately estimated by the application of a friction line and the use of the calm-water wetted surface. It is assumed that the dimensionless residuary resistance RR is the same for the model and the prototype vessel. Our article may be considered to be an extension of the classic article by Wilson, Wells, and Heber (1978) to the more complex case of the surface-effect ship, as follows. Specifically, we opine that:RT=RF+RW+RH+RS+RM+RSPRAY(2)Here, Rw is the wave resistance of the vessel (caused by a combination of the actions of the cushion pressure and the two sidehulls), RH is the transom (hydrostatic) drag, Rs is the seal drag, Rm is the momentum drag, and RspRay is the spray drag. Rt is the only one of these quantities that is measured during the model test. The other components require the use of a variety of estimates. In the article, we present specific examples of our approach as applied to a number of tests on surface-effect ship models that we have studied in recent years.

Study and Control of a Radial Vaned Diffuser Stall

The aim of the present study is to evaluate the efficiency of a boundary layer suction technique in case of a centrifugal compressor stage in order to extend its stable operating range. First, an analysis of the flow pattern within the radial vaned diffuser is presented. It highlights the stall of the diffuser vanes when reaching a low massflow. A boundary layer separation in the hub-suction side corner grows when decreasing the massflow from the nominal operating point to the surge and finally leads to a massive stall. An aspiration strategy is investigated in order to control the stall. The suction slot is put in the vicinity of the saddle that originates the main separating skin-friction line, identified thanks to the analysis of the skin-friction pattern. Several aspiration massflow rates are tested, and two different modelings of the aspiration are evaluated. Finally, an efficient control is reached with a removal of only 0,1% of the global massflow and leads—from a steady-state calculations point of view—to an increase by 40% of the compressor operating range extent.

Influence of the Slant Angle of 3D Bluff Bodies on Longitudinal Vortex Formation

This paper presents the experimental results and analytical arguments concerning simplified geometries of the rear window and windscreen of automotive vehicles in order to contribute to a better understanding of the swirling structure formation and vortex bursting processes. Static pressure distributions and skin friction line visualizations on both sides of the edge where the swirling structure is generated on the rear window of an Ahmed body are presented for different slant angles. Results show the influence of the slant angle on the swirling structure formation and further show that the vortex bursting process can be promoted by small rear window angles. These results are then extrapolated with the help of analytical demonstrations to the windscreen configuration to demonstrate that large windscreen slopes would have the same disintegration effect.

An Optimization Study for the Bow Form of High-Speed Displacement Catamarans

ABSTRACT Interest in high-speed marine transportation has acquired a wide variety of hydrodynamic research activities on catamarans, including shape optimization for minimum total resistance. This study attempts to utilize the mathematical programming in optimizing the bow form of twin hulls for minimum total resistance as well as in analyzing the optimization by physical model tests. The total resistance is assumed to be composed of wave-making and frictional components, which are formulated using Michell's thin-ship theory and ITTC-1957 friction line, respectively. The optimized hull form is analyzed by means of a computational flow solver before going through the experimental analysis. The study demonstrates the capabilities of the optimization procedure, presented for catamarans, in reducing the total resistance, as well as its limitations to be used as a design tool in a relatively high-speed zone.