Characteristics of a series of high speed hard chine planing hulls - part II: performance in waves

An experimental investigation into the performance of high speed hard chine planing hulls in irregular waves has been conducted. A new series of models representative of current design practice was developed and tested experimentally. Measurements of the rigid body motions and accelerations were made at three speeds in order to assess the influence of fundamental design parameters on the seakeeping performance of the hulls and human factors performance of the crew, with an aim to provide designers with useful data. Response data, such as heave and pitch motions and accelerations, are presented as probability distributions due to the non-linear nature of high speed craft motions. Additionally statistical parameters for the experimental configurations tested are provided and the most relevant measures for crew performance discussed. Furthermore, an example of the use of these statistical parameters to evaluate the vibration dose value of the crew onboard a full scale high speed planingcraft is given. It is confirmed that at high speed craft motion leads to recommended maximum values of vibration dose value being exceeded after only short durations. In practice, therefore, mitigating strategies need to be developed and/or employed to reduce crew exposure to excessive whole body vibratio

Race-time prediction for the Va’a paralympic sprint canoe

The 2016 Paralympic Games in Rio de Janeiro will see 200m sprint canoe events for the first time, using the Va’a class. The aim of this study is to predict race times for the Va’a over a 200m sprint event, through simulation of the hydrodynamic resistance of the hull (with outrigger) and the propulsion provided by the athlete. Such a simulation, once suitably validated, allows investigation of design and configuration changes on predicted race performance. The accuracy of the simulation is discussed through a comparison to times recorded for an athlete over a 200m race distanc

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

Intermolecular O-H...O and C-H...π(C5H5), and intramolecular C-H...O interactions in 2-(ferrocenyl)thiophene-3-carboxylic acid

The title compound, [Fe(C₅H₅)(C₁₀H₇O₂S)], an important precursor en route to organometallic donor-π-acceptor systems, forms dimers in the solid state through cyclic intermolecular carboxylic acid O-H...O hydrogen bonds, graph set R²₂(8) [O...O 2.661 (2) Å and O-H...O 175°]. Intermolecular Ccp-H...πcp interactions between the unsubstituted cyclopentadienyl (Cp) rings and Cthiazole-H...πcp interactions link neighbouring molecules into a three-dimensional network [C...Cg 3.753 (7) Å and C-H...Cg 156°, and C...Cg 3.687 (3) Å and C-H...Cg 129°; Cg is the ring centroid]. Intramolecular C-H...O interactions are present, graph set S(7) [C...O 2.925 (3) Å and C-H...O 120°, and the closest C-H...Sthienyl contact has a C...S distance of 3.058 (2) Å]

Simulation of ship manoeuvring performance in calm water and waves

Traditional manoeuvring and seakeeping theories do not usually include any study of the interaction of the manoeuvring and seakeeping performances of a ship. A unified mathematical model, which brings together both aspects of ship manoeuvring in a seaway, has been proposed by Bailey, 1999 [9] and a time simulation has been developed on this basis.This study summarises the principles of the unified mathematical model and the verification of software, in which preliminary results for a Mariner vessel are presented. Then it extends the use of the model for another ship, the British Bombardier tanker, in order to further the validation process. The influence of parameters of the model, such as the mesh or the viscous ramp used at low frequencies, is investigated. Then, the predictions of circle manoeuvres and zigzag manoeuvres are compared with full-scale trials results. The comparisons are detailed and it shows that, although non linear effects have to be considered, the software predicts good tendencies in the evolution of ship manoeuvring characteristics, when some parameters such as rudder angle change. The investigation finally includes a preliminary study of the effect of waves on the ship's manoeuvring characteristics, for following and head seas

Interdisciplinary research collegium in advanced maritime systems design

The education of naval architects, marine engineers and others who are the active contributors to the ship design processes is heavily focussed on engineering fundamentals, often aligned with traditional university course constraints. The concept of a research collegium is described whose aim is to provide an environment where young people in their formative postgraduate years can learn and work in a small, mixed discipline group drawn from the worldwide maritime community to develop their skills whilst completing a project in advanced ship design. The brief that initiates each project sets challenging user requirements which encourage each team to develop an imaginative solution, using their individual knowledge and experience, together with learning derived from teaching which form a common element of the early part of the collegiu