The nonlinear roll damping moment can be calculated in Aqwa time domain and frequency statistical analyses. For frequency domain solutions, the LDRG option should be added.

The following data record is required for the program to calculate this moment:

      2   5  7   11    16    21        31         
    - --- -- ---- ----- ----- --------- ---------  
   |X|   |  |QDRD|     |     |         |  
    - --- -- ---- ----- ----- --------- ---------  
       |  |   |     |     |       |
       |  |   |     |     |       |
       |  |   |     |     |       |_(3)Quadratic roll coefficient, Cd (F10.0)
       |  |   |     |     |
       |  |   |     |     |_(2)Node Number Two(I5)
       |  |   |     |
       |  |   |     |
       |  |   |     |_(1)Node Number One(I5)
       |  |   |
       |  |   |
       |  |   |_Compulsory Data Record Keyword(A4)
       |  |
       |  |
       |  |_Optional User Identifier(A2)
       |
       |_Compulsory END on last data record in data category(A3)

(1)-(2) These two nodes define the horizontal direction of the roll axis in the local structure axes (LSA), only the x and y coordinates of these nodes are used. The vertical coordinate utilizes the value associated with the structure center of gravity.

If any node number is less than or equal to zero, or is not defined, the roll axis is assumed to be along the x-axis of the local structure axes (LSA).

(3) The roll damping moment about the roll axis is calculated by