W Amin

Bio: W Amin is an academic researcher from Australian Maritime College. The author has contributed to research in topics: Slamming & Computational fluid dynamics. The author has an hindex of 8, co-authored 22 publications receiving 172 citations. Previous affiliations of W Amin include University of Tasmania.

Non-linear unsteady wave loads on large high-speed wave piercing catamarans

Abstract: The current work investigates the slamming characteristics of wave piercing catamarans through the analysis of sea trials data of the 98 m Incat sea frame “Hull 061”, built in Tasmania, Australia and currently serving in the US Navy combat fleet. The importance of this sea trials data is that the ship was tested in severe sea conditions to assess her suitability for military operations and to define her operational envelope. New signal processing techniques such as Wavelet Transforms are used in analysing slamming data for two main purposes, slamming identification and modal analysis in time and frequency domains simultaneously. The Wavelet Transforms were found superior to conventional signal processing tools such as Fast Fourier Transform and Short Time Fourier Transform. The structural strength of wave piercing catamarans is studied by introducing a novel sea trials analysis for structural performance assessment in an attempt to simulate real loading conditions. The methodology was tested on normal linear wave loading (without slamming) and was found satisfactory. A “Reverse Engineering” approach is introduced to predict slamming loads during sea trials by using the capabilities of Finite Element Analysis using the well known software PATRAN/NASTRAN1. To increase the efficiency of this approach, the load parameters, spatial location and distribution, were investigated through model tests of a similar but larger 112 m Incat hydro-elastic model in the Australian Maritime College towing tank facility. Based on pressure measurements, proper slam load models can be more accurately and efficiently introduced in the finite element analysis. Quasi-static analysis was first performed to examine its suitability to analyse such fast time varying loads. Difficulties in comparison procedures between numerical simulations and trials data have strongly highlighted the need for dynamic analysis. Direct transient dynamic analysis was performed using the dynamic solver of the same software package. Good agreement with trials data was found. The suggested procedure and slamming loading patterns used in the numerical simulation is then verified and can be regarded as a solid base for verification of other theoretical design models.

Numerical Prediction of Symmetric Water Impact Loads on Wedge Shaped Hull Form Using CFD

Abstract: Over the past two decades high-speed vessels have extended their service areas from protected waters to the open ocean where frequent and large water impacts can result in structural damage. The accurate prediction of slamming loads, and their consequences on light-weight high-speed vessels, is an essential element of efficient structural design. The aim of this work is to understand and accurately predict the behavior and local slam loads of quasi-2D wedge shaped hull forms impacting water. The computed results, using finite-volume Computational Fluid Dynamics (CFD), are validated against drop test experimental data and compared to a previously published numerical simulation using Smoothed Particle Hydrodynamics (SPH). The CFD results show good agreement with the experimental measurements.

Review of ship slamming loads and responses

Abstract: The paper presents an overview of studies of slamming on ship structures. This work focuses on the hull slamming, which is one of the most important types of slamming problems to be considered in the ship design process and the assessment of the ship safety. There are three main research aspects related to the hull slamming phenomenon, a) where and how often a slamming event occurs, b) slamming load prediction and c) structural response due to slamming loads. The approaches used in each aspect are reviewed and commented, together with the presentation of some typical results. The methodology, which combines the seakeeping analysis and slamming load prediction, is discussed for the global analysis of the hull slamming of a ship in waves. Some physical phenomena during the slamming event are discussed also. Recommendations for the future research and developments are made.

Hydrodynamic performance of a floating offshore OWC wave energy converter: An experimental study

Abstract: To investigate the dynamic response of a floating moored oscillating water column device under realistic sea states, a focused wave technique was developed in this study to generate user-defined wave trains in a wave basin equipped with a piston-type wavemaker. The experimental setup allowed for simultaneous measurements of the designed focused wave trains, internal chamber wave elevations and air pressure, dynamic tendon response and the model's global motion responses. Based on the experimental results it was found that to accurately replicate the theoretical wave time series, a minimal focal reconstruction of 200 components was required which resulted in a focused wave regeneration accuracy greater than 93% with strong repeatability. The tested model showed typical motion responses to that of generalised tension leg platform systems with significant surge offsets along with stiff heave and pitch motions. Applying vertical tendons to the system allowed for the floating offshore device to be exposed to deeper waters, and hence the larger energy source associated with deep water ocean waves.