ANSYS Aqwa Hydrodynamic Time Response

Workshop 2.2 14.5 Release

ANSYS Aqwa Hydrodynamic Time Response

Time Domain Simulation Open Workbench and open project using File > Open Browse to MooredShip.wbpj

Open Hydrodynamic System Double click on Model cell in the Hydrodynamic System System This is a similar model to that used in Workshop 2.1 and has already been solved. Close the Hydrodynamic System

Adding the time response

Drag and drop the Hydrodynamic Time Response to the WB Project Schematic while sharing the solution from hydrodynamic diffraction Double-click on Setup

Add fairlead connection points Add four fairlead locations for the mooring system Under Geometry in the Outline select Mooring Ship > Add > Connection Point Enter X,Y,Z coordinates in details panel as below (in global system!) Repeat for other 3 connection points •

Point 2 20, -14.2, 8

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Point 3 180, 16, 8

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Point 4 180, -16, 8

Rename Connection Points as Fairlead 1 through 4

Add anchor fixed points Add four anchor locations for the mooring system Under Model in the Outline select Geometry > Add > Fixed Point Enter X,Y,Z coordinates in details panel as below Repeat for other 3 fixed points •

Point 2 -1000,-1000,-500

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Point 3 1000,1000,-500

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Point 4 1000,-1000,-500

Rename Fixed Points as Anchor 1 through 4

Set up mooring line properties We are going to use composite catenary lines for the mooring system. These are lines made up of one or more segments with varying properties e.g. chain/wire/chain Select Connections > Catenary Data > Insert Catenary Data > Catenary Section. Note we can also define intermediate buoys and/or clump weights.

Mooring line properties Provide data for Mass/Unit Length, Equivalent Cross Sectional Area, Stiffness, Maximum Tension and Equivalent Diameter as below. Rename as LineProp1 •

Note we can also define bending stiffness, non -linear axial properties

Repeat for two additional sections

Mooring line connections To add a line select Connections > Insert Connection > Cable Choose Fixed Point & Structure for Connectivity and Non-Linear Catenary for Type We need to define end connection points and the segments along the line, plus some data defining the possible dZ range of the fairlead (explained in Workshop 3.2). Rename mooring line as Cable 1

Mooring line connections Click on cell adjacent to Fixed Point and select Anchor1 (Fixed) from drop down menu. Click on cell adjacent to End Connection Point and select Fairlead 1 (MooringShip) from drop down menu.

Mooring line configuration The composition of the line is now defined •

Segment allocation

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Line length

Segments are defined from the anchor location up to the fairlead Section 1 type should be set to LineProp1 Length 400 m Repeat for sections 2 and 3 as shown Finally set the Positive dZ Range under Cable Properties to 10m

Mooring line configuration Repeat these steps for the other three lines

Mooring line configuration Note that as you construct the line configuration the line properties are reported in a window called Catenary Cable Definition Data The Joint 1-2 etc refers to connection data such as clump weights weights or buoys

Mooring line configuration Select Connections in the Outline to see s ee the final mooring configuration configuration

Time domain simulation options Set Analysis Type to regular wave response Set Use Cable Dynamics to No Set Convolution Convolution to  to No Set Finish Time to 180 seconds

Define the environment RMB on Hydrodynamic Time Response > Insert > Regular Wave Set Wave Type to Airy Wave Theory Set Amplitude to 1 m Set Period to 10 s Set Direction Direction to  to 90 degrees Run the analysis by clicking on Solution and

Check the solution RMB Solution to Insert Result > Structure Position > Actual Response Select the Global Z as the mode of motion and generate the graph (RMB Evaluate All Results)

Check the solution Add a second graph item -Insert Result > Cable Forces > Whole Cable Forces Select Tension for Cables 1 and 3 Evaluate All Results

Irregular wave simulation RMB Regular Wave and Suppress

Change the Analysis Type in Analysis Settings to Irregular Wave Response and set Convolution to Yes RMB on Hydrodynamic Time Response to Insert > Irregular Wave Pierson-Moskowitz

Set Irregular wave characteristics Set Direction Direction to  to 90 degrees Set Seed Seed to  to 10001 (this is used to generate the random phase relationships of the wave components) Set Start Frequency to 0.1 rad/s Set Finish Frequency to 2.0 rad/s Set Significant Wave Height to 0.88 m Set Zero Crossing Period to 10 s

Set Analysis Settings and Solve Set Finish Time to 1200 s Run the analysis by clicking on Solution and

Setting up parameters For design studies, several input parameters can be set as variable (such as environmental parameters) Click the square on the left hand side of the Significant Wave Height on the Irregular Wave Details P in the box will indicate that this value is a variable parameter and the value input box will be locked

...Setting up parameters Go back to Project Schematic You will see that the Parameter Set box has appeared. D-Click on the Parameter Set box

Design Points View Design Points view in workbench consists of several sub-views; •

Outline of all parameters

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Table of design points

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Properties

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Chart

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Parameters Chart Toolbox

Setting up output parameters Go back to the Aqwa window. Select the Cable Forces Result Set the maximum value of Line B as an output parameter (this will enable design point computations to be automated) Under Analysis Settings set Time Step to 0.25 s and Finish Time to 600 s (will reduce total solution time)

Setting up output parameters You will see in Outline of All Parameters window that this value is set as an Output Parameter

Setting up Design Points Go to Table of Design Points Input more periods as design points Click

The solution will take several minutes, so be patient.

Note the Exported column. If one or more of these boxes are checked then the results for that particular design point(s) will be saved. Otherwise only the initial design point (marked as Current) is preserved.

Results of Parameter Studies You can observe the result of the outputs in tabular form in Table of Design Points

... Results of Parameter Studies You can also plot them from the Parameter Charts Toolbox Select Outline Of All Parameters to see the Toolbox D-click on Parameters Chart Select X axis and Y axis parameters from Properties of Outline The resulting plot will be observed in Parameter Chart window (Note that line p roperties may be modified by RMB on the line and select Edit Properties)