Application of simulation technology to the performance evaluation of HMS Victory as an exemplar of the ships at the battle of Trafalgar

Summary:The production of a computer-based simulation representing an early 19th Century sailing warship is described. HMS Victory is used as a basis ship throughout the work. A broad overview is presented of the goals of the project. The particulars of HMS Victory are given and basic hydrostatic data calculated. The design and construction of both a 1:40 towing tank and wind tunnel scale models are described. The experimental procedures used during both sets of tests are detailed, along with the subsequent data analysis. Sample results are presented and regression functions fitted for use within the simulation. The software design decisions are outlined before the overview of Virtual Trafalgar's software architecture is presented. The implementation of the ship manoeuvring theory in the simulation physics engine is described and results from initial evaluations given

Development of high performance composite bend-twist coupled blades for a horizontal axis tidal turbine

Development of a design methodology for a composite, bend-twist coupled, tidal turbine blade has been undertaken. Numerical modelling was used to predict the response of the main structural member for the adaptive blade. An experimental method for validation is described. The analysis indicates a non-linear blade twist response

Use of cryogenic buoyancy systems for controlled removal of heavy objects from the seabed

The concept design of a lightweight cryogenic marine heavy lift buoyancy system has been investigated. The approach makes use of a novel cryogenic system for provision of buoyancy within the ocean environment. The objective is to be able to lift or lower large displacement objects under full remote control. The nature of subsea lifting and lowering operations requires a high degree of precise control for operational safety, reasons and to preserve the structural integrity of the load. The lift operation occurs in two phases: Development of lift to overcome seabed suction, and then rapid reduction of buoyancy to maintain a controlled ascent. Descent involves controlled release of the buoyancy. The proposed buoyancy system consists of a buoyancy chamber and an integral cryogenic gas generation unit. The application of an on-board gas generation unit allows the removal of the engineering challenges associated with use of compressors and the concomitant complex manifold of connecting umbilical pipe work. It provides for a fully remote system completely eliminating all risk associated with extensive physical surface to subsea connection throughout the entire lift operation. The opening stages of the project work include the development of a system that will operate efficiently and effectively to a depth of 350m. An initial general arrangement for the buoyancy system has been developed. A number of these systems involve considerable design and development, these include: structural design of the buoyancy chamber, mechanical systems to control and connection to the lift device, the cryogenic system itself and overall process control systems. As part of the design process for such an arrangement, numerical simulation of the complete system has been undertaken in order to develop mechanical, cryogenic and process control systems efficiently and effectively. This system simulation has been developed using Matlab Simulink. This paper considers the overall design concept and associated system development issues. These are illustrated through use of the time accurate simulation of alternative design configurations that confirm the viability of the concept. A main conclusion is that minimisation of the dry weight of the system is critical to cost-effective operation of the project

Fluid-structure interactions of anisotropic thin composite materials for application to sail aerodynamics of a yacht in waves

In recent years technological innovations has allowed large improvements to be made in sail design and construction. Sails and in particular kite-sails have application for sport, ships’ auxiliary propulsion and even power generation. Sails are divided into upwind and downwind sails (Fig.1), where upwind sails operate as lifting surfaces with small angles of attack whereas traditional downwind sails acted as drag device. New designs of downwind sails have reduced the area of separated flow and increased the lifting behaviour of the sails. In order to capture the lifting behaviour and regions of separation present in both types of sail careful application of computational fluid dynamic analysis tools are required. Solutions of the Reynolds averaged Navier- Stokes equations (RANSE) are often used as a part of the design process of high performance sailing yachts.The present paper discusses some initial investigations and future guidelines in order to get a more detailed description of the physics involved in sail FSI. Three main fields are therefore covered: the use of CFD in order to accurately capture flow features and a comparison with experimental results; structural modelling; and approach to couplin

Wind tunnel tests on the effect of a ship hull on rudder-propeller performance at different angles of drift

This report presents the experimental results from a series of wind tunnel tests. The tests investigated the influence of various upstream bodies on the performance of a representative ship rudder-propeller combination for different angle of drift. All the tests were carried in the 3.5m x 2.5m low-speed wind tunnel at the University of Southampton and are an extension to basic rudder-propeller tests which have already been carried out and are reported elsewhere. The model rudders tested were all-movable and the model propeller used was based on a Wageningen B4.40. Rudder forces and moments and propeller thrust, torque and revolutions were measured for all conditions tested. A standard series of flow conditions were used. These were free-stream flow (no propeller present) and tests at propeller open-water advance ratio of J of 0.94, 0.51 and 0.36. For these conditions, forces were measured at rudder angles between -40 degrees and +40 degree. In addition, a select sample of tests were carried out for both larger rudder incidence and for tests in the second quadrant and at a low advance ratio J of 0.17.Three types of test were carried out:1) the rudder-propeller combination alone was tested at drift angles of -15 degrees, -7.5 degrees, +7.5 degrees, and +15 degrees;2) at two angles of drift of -15 degrees and +7.5 degrees, three different lengths of centre-board were place upstream of the rudder-propeller combination to simulate the effect of a thin upstream hull on performance;3) at two angles of drift of -15 degrees and -7.5 degrees a representative ship hull form based on the stern of the Mariner class of vessels was mounted upstream of the rudder-propeller combination to assess the influence of hull thickness.Pressures were measured at 200 locations distributed over the rudder surface for the rudder-propeller combination alone and the results are given as both chordwise pressure distribution for eight spanwise locations and as distributions of spanwise sectional load distributions.The results give an essential insight into the behaviour of flow around the stern of a vessel providing rudder force data for use in more realistic manoeuvring simulations and detailed data for the validation of numerical models of the ship rudder-propeller-hull interaction problem

An analysis of a swimmer’s passive wave resistance using experimental data and CFD simulations

The passive resistance of a swimmer on the free surface has previously been researched experimentally. The contribution of wave resistance to total drag for a swimmer with a velocity around 2.0 m.s-1 was found to vary from 5% for Vorontsov and Rumyantsev (2000), to 21 % for Toussaint et al. (2002) and up to 60% according to Vennell et al. (2006). The exact resistance breakdown of a swimmer remains unknown due to difficulties in the direct measurement of wave resistance. As noted by Sato and Hino (2010), this lack of experimental data makes it difficult to validate numerical simulations of swimmers on the free surface.This study is therefore aimed at presenting direct measurements of a swimmer’s total drag and wave resistance, along with the longitudinal wave cuts which may be used to validate numerical simulations. In this paper, experimental data of a swimmer’s resistance are presented at two different velocities (case 1 = 1.7 m.s-1 and case 2 = 2.1 m.s-1). Total drag was measured using force block dynamometers mounted on a custom-built tow rig (Webb et al., 2011). Moreover, a longitudinal wave cut method was used to directly evaluate wave resistance (Eggers, 1955).The two conditions tested were simulated using the open-source Computational Fluid Dynamics (CFD) code OpenFOAM (OpenFOAM® (2013)). The body geometry is a generic human form, morphed into the correct attitude and depth using the above- and under-water video footage recorded during the experiment. 3D Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations were performed using the Volume of Fluid (VOF) method to solve the air-water interface. A similar numerical technique was used by Banks (2013a) to assess the passive resistance of a swimmer. Two cases were simulated and the error in total drag compared to the experimental data was found to be 1 % and 22 % respectively. In this paper, the resistance components over a swimmer’s typical range of speeds are investigated and compared with the experimental dat

The effect of swimsuit resistance on freestyle swimming race time.

It is known that swimming equipment (suit, cap and goggles) can affect the total resistance of a swimmer, and therefore impact the resulting swimming speed and race time. After the 2009 swimming world championships (WC) the international swimming federation (FINA) banned a specific type of full body suit, which resulted in an increase in race times for subsequent WC events. This study proposes that the 2009 suits provided a reduction in swimming resistance and aims to quantify this resistance reduction for male and female freestyle events. Due to the practical difficulties of testing a large sample of swimmers a simulation approach is adopted. To quantify the race time improvement that the 2009 suits provided, an equivalent 2009 “no-suit” dataset is created, incorporating the general trend of improving swimming performance over time, and compared to the actual 2009 times. A full race simulation is developed where the start, turn, underwater and surface swimming phases are captured. Independent resistance models are used for surface and underwater swimming; coupled with a leg propulsion model for underwater undulatory swimming and freestyle flutter kick, and a single element arm model to simulate freestyle arm propulsion. A validation is performed to ensure the simulation captures the change in swimming speed with changes to resistance and is found to be within 5% of reality. Race times for an equivalent “no-suit” 2009 situation are simulated and the total resistance reduced to achieve the actual 2009 race times. An average resistance reduction of 4.8% provided by the 2009 suits is identified. A factor of 0.47 ± 10%, to convert resistance changes to freestyle race time changes is determine

Technical manual and user guide for the surface panel code: PALISUPAN

This report describes the theoretical background and the method of use of a general purpose lifting surface panel code Palisupan. This code, originally developed in Occam for use across arrays of transputers, has been rewritten in ANSI C and a serial version is available for use on Unix based machines. The code uses dynamic memory allocation to maximise the available problem size for a given computational environment. The two available methods for preparing geometry definition files are described as are the production of various types of post-processing information. A section describes the importance of the validation process. An exercise in the form of a validation tutorial introduces the user to the limitations of three-dimensional potential flow analysis using a surface panel code. A final section describes an assignment for users to implement in order to develop increased familiarity with the solution of a practical design problem. In this case the analysis of yacht keel-bulb hydrodynamic performance