PSI - Issue 45

Mark Mogeke et al. / Procedia Structural Integrity 45 (2023) 36–43 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

39

4

GPS

SG-1

SG-3

SG-2

Fig. 1. (a) Royal Australian Navy HMAS Maryborough (II), and (b) schematic of profile view showing analysed strain gauge locations.

The presented analysis employs measurements of strain, acceleration, and ship speed acquired from the HMS. Data from three of the strain gauges is analysed (Table 1). Fig. 1b is a schematic of the ship’s profile and these strain gauge locations.

Table 1. Analysed sensor locations. ID Approximate location

Sample rate SG-1 Port side, underside of main deck plating, approx. 2925 mm off centreline 50 Hz (0.02 s) SG-2 Centre of flange on keel 100 Hz (0.01 s) SG-3 Port side, underside of main deck plating, approx. 2925 mm off centreline 50 Hz (0.02 s) GPS Top of mast ~0.0625 Hz (~16s)

2.3. Wave environment data sources

2.3.1. Wave buoy (deployed during sea trials) Wave buoy observations are considered an accurate method to obtain significant wave statistics because they directly measure the ocean surface. During the operational period of the HMS installed on Maryborough (II), a set of sea trials were conducted which included direct measurement of the wave environment (non-directional data) using a modified Micro Air-Launched Expendable Wave Buoy (MAXWB). (QinetiQ North America, No date) The sea trials were conducted from 31 May to 2 June 2016 and involved HMAS Maryborough (II) conducting runs at fixed speed and heading relative to waves (10, 15, 20, and 25 kn) and (0°, 45°, 90°, 135°, 180°), respectively. We consider measurements from the MAXWB installed to be the “source of truth” during these trials. 2.3.2. Wave hindcast In addition to wave buoy measurements, hindcasting provided another method of obtaining wave environment data. Only free and open-source data sources were utilised for hindcasting and are summarised below:  Copernicus Marine Environment Monitoring Services (CMEMS) – The European Union’s CMEMS provides data and services on a global and regional scale. The GLOBAL_REANALYSIS_WAV_001_032 is a global wave re-analysis of past sea states from 1993 to 2019. The model is based on the Meteo France Wave Model (MFWAM), a third generation wave model takes into account oceanic currents from GLORYS12 physical ocean reanalysis, and assimilates significant wave height observed from historical altimetry missions and directional wave spectra from a number of satellites (Chune, 2019, Chune et al., 2020). Temporal and spatial resolution are 3 hrs and 0.2°, respectively.  National Oceanic and Atmospheric Administration (NOAA) – The United States’ NOAA provides free and open- source marine data in addition to NOAA’s WAVEWATCH III (WWIII), described in Tolman (1991), is a hindcast spectral wave model consisting of different global and regional grids. The input forcing fields are wind input from the Global Forecast System and algorithm-generated ice fields. No wave data assimilation is performed. Temporal and spatial resolution are 3 hrs and 0.5° respectively  Collaboration for Australian Weather and Climate Research (CAWCR) – Australia’s Bureau of Meteorology and Commonwealth Scientific and Industrial Research Organisation provides higher resolution data on a local scale (Australiana and Western Pacific regions in the aus_4m dataset). Using WWIII (TEM) version 4.18,