And the variation of effective tension at both cable ends can reach 1.67 times that of cable ends under usual random waves. When extreme waves appear, pitch, heave and heave acceleration of the laying ship and tension of the cable ends increases obviously. The current also has some influences on the submarine cable laying, and the maximum effective tension of cable produced by the combined wave-current action is 1.35 times that of cable with the wave action alone. Research results show that the tension and curvature of the cable are large under the condition for wave direction perpendicular to the ship axial direction, which is a relatively bad sea condition. Moment on beam at node A (kNm, kNm, kNm), axis system of node A. The beam arrives at this axis system along the X-axis. The axis system that the B-end of the beam is connected to. The beam leaves this axis system along the X-axis.
usual waves, waves with current combined and possible extreme waves. The axis system that the A-end of the beam is connected to. The motion response of laying ship and the hydrodynamic characteristics of submarine cables are simulated here under three sea conditions, i.e.
Orcaflex coordinate system software#
The numerical model is established with the Orcaflex software employed. Coconut Creek (Florida), ISSN 0749-0208.īased on real sea conditions of the national wave energy demonstration site in Wanshan sea area of Zhuhai City, China, some numerical experiments are carried out to simulate the submarine cables initial laying process of the Wave Energy Booster Station in this demonstration site. Then, the data is imported into OrcaFlex software, and the model of lifting system is established in OrcaFlex. Journal of Coastal Research, Special Issue No. The lifting pipe is vertical and a three-dimensional coordinate system X. (eds.), Air-Sea Interaction and Coastal Environments of the Maritime and Polar Silk Roads. Numerical study on initial laying process of submarine cables for wave energy booster station in real sea states. Most of the data and results are given relative to the global axes, including the positions of objects, current and wave directions. The coordinate system used in Orcaflex is shown in Figure 7.1. For non-periodic files, if extrapolation in time is required it is performed by clipping to the defined range.Hu, J. Orcaflex uses one global coordinate system (GXYZ) and a number of local coordinate systems (Lxyz), generally one for each object in the model. Graphical view of the closed loop simulation with Matlab-OrcaFlex. If the file is periodic, as recorded in the file header, OrcaFlex will interpret the data accordingly. A fixed reference frame is defined as an orthogonal reference frame whose -axis is. bts file format supports periodic time histories. If you have the wind speed $v(h)$ at some other height h (in metres), then the wind speed $V(10)$ at 10m can be estimated using the formula $v(10) = v(h)\,(10/h)^$ respectively. Figure 31 shows the vessels offset to the initial reference system. If you are using the OCIMF model for wind load on vessels, the speed is expected to be that at an elevation of 10m (32.8 ft) above the mean water level (MWL). Figure 10: OrcaFlex 10.2d Calculation Definition. Negative factors may be used, allowing you to model reversing wind profiles.Ī value of '~' means that there is no vertical variation. To do so, you define a vertical variation factor variable data source. To specify a vertical wind speed profile, you may define the wind speed variation with height above the mean water level (MWL) as a dimensionless multiplicative factor. Wind speed is assumed to be the same at all heights, unless a vertical wind speed profile is specified. The value here is fixed and cannot be edited. The air density is assumed to be constant and the same everywhere. Unless otherwise stated the parameters listed above will be Dt 0:2, n e 10 and q 0 270 ‘for beam sea and q 0 225 ‘for quartering sea. You may choose whether or not wind loads are included for vessels, lines, 6D buoys and 6D buoy wings. ORCAFLEX followed by a comparison of their respective per-formance in regards to natural periods, element and time step convergence and the stochastic response in beam sea and quarter-ing sea. 6D buoys – see lumped buoy added mass, damping and drag and spar buoy and towed fish drag.Lines – see hydrodynamic and aerodynamic loads.
OrcaFlex includes the effects of wind on: