Learning Forum

[ashwin Gurjar]

In Ansys Aqwa, there is an option to account for drag forces on the diffracting structure. Here,

• X_X: Force (coefficient) in the X-direction (surge) due to velocity in the X-direction.

• Y_Y: Force in the Y-direction (sway) due to velocity in the Y-direction.

• Z_Z: Force in the Z-direction (heave) due to velocity in the Z-direction.

• RX_RX: Moment about the X-axis (roll) due to angular velocity about the X-axis.
• RY_RY: Moment about the Y-axis (pitch) due to angular velocity about the Y-axis.
• RZ_RY: Moment about the Z-axis (yaw) due to angular velocity about the Z-axis.
  Is this the correct interpretation? I am unable to understand how to fill this matrix for an asymmetric body.
  how to calculate the rotation drag coefficient? i.e. (Rx_RX), (RY_RY) and (RZ_RZ)? from fluent.
•  From fluent, 3 forces and 3 moments are obtained by flow along X(surge ), and it can be updated in the matrix, similarly for surge and heave. But how to update the entry of rotational RX-RX or off-diagonal RX_RY, etc?
  

[Shuangxing Du]

From Fluent, as the flow is along x direction, instead of using Morison hull drag coefficients, could you please using Current hull drag coefficients (see 7.1. Current and Wind Hull Drag)? For the detailed information on Morison hull drag, please see 7.4. Morison Hull Drag Force.