ANSYS AQWA

A major development for the ANSYS AQWA suite is the introduction of a new module AQWAWB, which provides a Workbench style interface that allows importation of ANSYS DesignModeler geometry files, offers integrated meshing, and is able to undertake a Diffraction/Radiation analysis directly within the new environment. This represents the first stage in fully incorporating the ANSYS AQWA capabilities within ANSYS Workbench.

Major features include:

Built in Meshing

Using the ANSYS meshing algorithms to mesh the geometry, this means that manual input of node and element data is no longer required. The mesh size can be adjusted and it can be regenerated easily.

Validation of Input

All data input is in Workbench style tree objects, this means that it can be validated before performing the analysis. For most inputs there is also on screen graphical representation so that the positions, or directions of application, can be visually checked. Where there is a fixed range the entry will be highlighted if it is outside the permitted range.

Visual and numerical checking may be undertaken through the interface

Built in Results Viewing

Within the single environment you are able to view the hydrostatic report along with graphs that pertain to diffraction/radiation calculations. Furthermore, the pressures and motions that the structures are subject to can be displayed and animated, with the possibility to export the animation in a standard format.

The ANSYS AQWA to Microsoft Excel Interface AQL Has Been Extended with More Commands

Some new functions have been added to AQL, the interface between AQWA and Microsoft Excel:

Function	Value returned
aqltharticulation	Articulation reactions from time history analysis
aqlthfender	Fender results from time history analysis
aqlthnumsteps	Number of timesteps in a time history analysis
aqlglobal	Global parameters (depth, density, gravity)
aqlzcge	ZCGE value

For ANSYS Users the Performance of the ANSYS to AQWA Translator Has Been Improved

The capability to write out an AQWA data file from an ANSYS Mechanical model is now a command within ANSYS, rather than an APDL macro. This means that it runs much faster than previous versions.

Improved Lid for Standing Waves

The VLID card controls the creation of a lid that can be used to suppress standing waves between structures. The formulation of this lid has been significantly improved.

Hydrodynamic Interaction with Forward Speed

AQWA can now calculate hydrodynamic interaction between structures which have forward speed, as long as they have the same velocity.

Maximum Number of Interacting Structures Increased to 20

The maximum number of hydrodynamically interacting structures in a model has been increased from 10 to 20.

Print Hydrodynamic Database to ASCII File

It is often required to obtain a textual version of the hydrodynamic data created by AQWA, and this is generally only available from the .LIS file. The format of this is not constant, and changes can be inconvenient if software is written to extract this data from the listing file. It is now possible to request an ASCII output of hydrodynamic data in a concise format using a new AHD1 option.

Mooring Section Tensions Written to .PLT File

If mooring section tensions are requested using the PMST card, they are now written to the .PLT file as well as the .LIS file.

Use Current Profile for Hull Drag

It has long caused confusion that a profiled current was only applied to Morison elements, and was not used for calculating the drag force using drag coefficients in Deck 10. It is now possible to request that hull drag loading is computed from a specified current profile.

Re-Calculation of 2nd Order Forces

Any change that causes the RAOs to change (for example, re-running with additional damping) also affects the drift coefficients, because part of the drift force calculation depends on the RAOs. Until now the drift coefficients were not re-calculated, which could lead to a situation where the RAOs and QTFs in a database were inconsistent.

This has now been changed so that the QTFs are re-calculated when the RAOs change. They are also re-calculated when databases containing different sets of frequencies are merged. As a result of this merging and re-calculation it is not possible to allow so much flexibility and the DELF and MVEF cards in Deck 6 have been withdrawn.

The re-calculation of QTFs also means that the potentials and source strengths must always be available, and so the functions of the LDOP option (output of .POT and .USS files) are now always switched on.

Allow Longer File Names

It has long been a source of irritation that the names of AQWA data files were restricted to 12 characters (8 followed by the extension .DAT. Although full windows compatibility has not yet been achieved, the maximum length of file name has been increased to 32 characters (28 plus .DAT). The total length of path + filename is limited to 135 characters.

Consistent Encounter Frequency of Associated Structures in FER

When structures are connected by mooring lines or articulations, AQWA-FER now checks that they all have the same forward speed (or current). If the speeds are different it will use the maximum when calculating encounter frequency for all the structures.

Conversion to IVF

A major development in version 12.0 is the conversion to use the same Intel Visual Fortran compiler as the rest of the ANSYS programs. This is giving a considerable increase in speed compared to previous versions, although the increase will vary from one analysis to another. This change in compiler will also help facilitate future integration with other ANSYS tools, and provides the basis for taking advantage of multi-core processors and distributed networks in the future.

One consequence of the conversion is that the format of direct access binary files such as the .RES, .HYD and .PLT files has changed. When importing an “old” format file from v5.7 into v12.0, AQWA will convert the file and save a copy of the old file with a new name. This means that if you then attempt to import the same file into v5.7, you will get an error.

Performance of version 12.0 with previous version 5.7D

Test #	Description	5.7D	R12	%
1	LINE - Half symmetry model, 4860 diff elements	1267	562	44.36
2	DRIFT - Cable dynamics	7158	3771	52.68
3	DRIFT - TLP	2967	1275	42.97
4	NAUT - Quasi-static moorings and fenders, multi body	5650	3054	54.05
5	DRIFT - Cable dynamics, multi body including TUBEs	4074	2242	55.03
7	LINE - Double symmetry, 5217 diff elements	5794	2470	42.63

Microsoft Windows Vista and 64-bit

Version 12.0 of AQWA will run on Windows Vista and 64-bit operating systems. Although it is still using 32-bit architecture (i.e. it is not using the extended memory capabilities of 64-bit OS) it has been fully tested to run in a 64-bit environment.

More Flexible Ordering of Articulations

Previously it was necessary to define a chain of articulations in order along a model. In complex models it was sometimes necessary to try different orders for the articulations before a satisfactory solution was obtained. This requirement has now been removed. Unlike a FE program there is no fixed support so it is still necessary for the program to “consolidate” the articulations, but the order is now determined internally, usually starting with the most massive structure.

AQWA-LIBRIUM Creates .PLD File

When using AQL to import AQWA results into Excel, data is read from the .PLD file. Previously this file was not created automatically by AQWA-LIBRIUM, meaning that the files had to be opened in the AGS before AQL could be used. AQWA-LIBRIUM now always writes out the .PLD file.

Wave Grid Calculated by AQWA-LINE

When using the AGS to plot wave surface heights or pressures, it was always necessary to wait while the program created a .PAG file (pressures at grid points). Using a new SEAG card in deck 2, this file can now be created at the end of the AQWA-LINE analysis, meaning that there is no delay when using the AGS.

Installation and Licensing Changes

• ANSYS AQWA will be included on the ANSYS V12 Installation Package along with all the other ANSYS products. This will make installation more straightforward, particularly as many users license other ANSYS products.
• The ANSYS License Manager will be employed for AQWA. Although this is based on the FLEXlm licensing system currently used, ANSYS have added a ‘wrapper’ which guides the user towards a successful installation. Again, for those users who have other ANSYS products besides AQWA, it will mean only one licensing system is employed. It should be noted, however, that the two versions are not compatible; the ANSYS License Manager will ONLY work with V12 products, and the AQWA License Manager will ONLY work with the existing (or prior) versions.