Slamming loads of ships - experimental approaches

Over the past century, considerable research efforts have been spent to accurately predict slamming loads on marine structures using both experimental and theoretical approaches. However, very limited three-dimensional (3D) tests have been conducted on catamaran vessels and as such it is not currently possible to validate numerical predictions for 3D catamaran hullforms impacting water. The aim of the present work is to provide researchers and designers with available experimental techniques to assess slam loads. The study highlights the pros and cons of three techniques that were employed to charactrise wetdeck slamming loads. Results of recent seakeeping tests, and 3D water-impact tests at approximately constant relative velocities are discussed. The results of the seakeeping tests that were conducted at the Australian Maritime College, deemed to be realistic and logical when compared with results of constant speed water impact tests. However, due to the complexity associated with towing tank experiments and the relatively high cost, this approach might not be available for many researchers and designers. By reviewing the advantages and limitations of both the free-falling drop test technique and the controlled speed water impact tests, a proposed gas-gun impact facility could present a promising technique. In this technique the model is propelled with an actuator (compressed gas gun) to the required velocity, then allowed to fall into the water freely. This technique would enable researchers to measure the slam loads at more realistic corresponding velocity traces.