11.5.5. The WDGA/WDGD Data Record - Wave Frequency Diagonal Added Mass and Wave Frequency Diagonal Damping

These data records represent a more convenient manner to input the added mass matrix (WDGA) and linear damping matrix (WDGD) at the frequency/period specified on the preceding FREQ/PERD/HRTZ data record, when there are no off diagonal terms coupling the degrees of freedom of motion. They are used instead of the data records WAMS and WDMP respectively, which are used only when these coupling terms exist. If the added mass or damping matrix has been read from backing file, the WDGA or WDGD data record will replace (i.e. overwrite) the existing values within that matrix. See also the note at the end of this section, when using Aqwa-Line.

      2   5  7   11        21        31        41
    - --- -- ---- --------- --------- --------- ------
   |X|   |  |WDGA|XXXXXXXXX|         |         |      ...
    - --- -- ---- --------- --------- --------- ------
   |X|   |  |WDGD|XXXXXXXXX|         |         |      ...
    - --- -- ---- --------- --------- --------- ------
       |  |   |                 |         |         |
       |  |   |                 |----------------------
       |  |   |                 |
       |  |   |                 |_(2)-(7)6 Mass/Inertia or Linear Damping Values(6E10.0)
       |  |   |                         
       |  |   |
       |  |   |_(1)Compulsory Data Record Keyword(A4)
       |  |
       |  |_Optional User Identifier(A2)
       |
       |_Compulsory END on last data record in data category(A3)

(1) This data record keyword indicates whether the values (3) refer to the added mass matrix (WDGA) or to the damping matrix (WDGD)

(2)-(7) These are the values which replace those in the leading diagonal of the added mass/damping matrix. All other elements of the matrix are set to zero.

Note: Effect of the WDGA/WDGD Data Record when Using Aqwa-Line

Input of the wave frequency added mass/damping matrix is redundant information when running Aqwa-Line as the program normally calculates these matrices. Therefore, use of a WDGA/WDGD data record will instruct Aqwa-Line not to perform a radiation/diffraction analysis at this frequency. You must then specify all other parameters which would otherwise be calculated at this frequency, i.e. the linear damping/added mass matrix, Froude Krylov and diffraction forces.

These data records are not valid for a structure with forward speed in multiple wave directions.