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These are reference origins, phase origins, the rotational inertia matrix and the centre of buoyancy. WAMIT uses a horizontal reference frame for reporting its output, but some quantities that are imported into OrcaFlex need to be expressed using the OrcaFlex vessel axes. Again, and for similar reasons, these values must be set before importing WAMIT data.
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In a WAMIT analysis where the hull model represents a vessel at non-zero heel and trim, those angles should be entered as the datum rotations for the OrcaFlex vessel type. This is why the OrcaFlex vessel centre of mass must be set before import. out file (which are relative to the WAMIT vessel origin) and the centre of mass coordinates of the OrcaFlex vessel type (which are relative to the OrcaFlex vessel type origin). OrcaFlex deduces the position of this WAMIT vessel origin, relative to OrcaFlex's vessel origin, from the difference between the centre of mass coordinates in the. You must ensure that the vessel type centre of mass coordinates are set appropriately in OrcaFlex before importing WAMIT data.Īlmost all of the WAMIT data (with momentum-conservation QTFs being the sole exception) have their reference origin at WAMIT's vessel origin. Position vectors used for reference during import of hydrodynamic data from WAMIT If the length unit cannot be determined then the raw data will be imported from the file unscaled and a warning will be issued. If this is successful, then OrcaFlex will convert the data from non-dimensional to the units prevailing in the OrcaFlex model, using WAMIT's length scale $L$ (converted to the length unit of the OrcaFlex model) and the current OrcaFlex values of $g$ ( acceleration due to gravity) and $\rho$ ( nominal water density), using the scaling factors defined in the WAMIT user manual. The length unit in use in the file will be determined, if possible, from the value of $g$ and the knowledge that the unit of time is the second. Similarly, the control surface option is not available for the Newman QTFs. But in this particular file the load RAOs results are present for the diffraction method only, so the Haskind option is disabled and may not be selected in this case.
#Conversion orcaflex coordinate full#
In this example, a choice may be made between the different calculation methods employed by WAMIT for the Newman QTFs and the full QTFs. out file you have selected, as illustrated in the following figure: The requested data page of the import vessel data form allows you to choose between the methods that are available in the.
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Choice of calculation methodsįor some types of data (load RAOs, Newman QTFs, full QTFs) WAMIT may offer results from various different calculation methods. The data are almost all non-dimensional, the main exceptions to this being acceleration due to gravity $g$, and WAMIT's length scale $L$, used to non-dimensionalise the data. out extension and OrcaFlex can import data from such a file. These issues should be given a due consideration in calculations of ecological risks and EIA of any moored objects.WAMIT outputs its results to a text file with an. due to changes in biogeochemical cycling and light penetration. In addition to the direct effect on benthic habitats, sediment erosion by mooring lines will effect a whole range of ecosystem processes, e.g. In regular waves of 6 m height and 8 s period, the area of benthic habitats adversely affected by the mooring lines may exceed 60 m 2. The results show that the area of benthic habitats adversely affected by the leading mooring line on a typical wave energy converter (WEC) monotonically increases with the increase in wave height.
#Conversion orcaflex coordinate series#
The output from OrcaFlex is then imported to Matlab, where the affected area is calculated using the time series of coordinates of touch down points of the mooring lines. An OrcaFlex model is used to assess the scouring effect on bottom sediments and consequent disruption of benthic habitats, and open water tests are being conducted to compare the model performance with the actual observations. This paper presents the research carried out in the marine renewables group of Heriot-Watt University, where the physical models of wave energy converters are first tested in the wave basin, and the results of their behaviour are then compared to the simulations performed using mathematical modelling.