Monitoring Force Balance, Trim, and Velocity

You create several reports for the different forces such as drag, trim, and the virtual disk force components. In addition, you compute the net force in the X direction as this falls to zero when the vessel reaches its steady state velocity.

To set up reports required in monitoring the net force in the X direction:
  1. Create a report for the total drag over time:
    1. Right-click the Reports node and select New > Flow / Energy > Force.
    2. Rename the Force 1 node to Drag.
    3. Select the Drag report and set the following properties:
      Property Setting
      Direction [-1.0, 0.0, 0.0]
      Parts (Regions)[Domain:Deck, Domain:Hull, Domain:Stern]
  2. Create a report for the trim:
    1. Right-click the Reports node and select New > DFBI > 6-DOF Body Orientation.
    2. Rename this report to Trim Down.
    3. Select the Trim Down report and set Angle Report Option to Rotation Y Axis.
  3. Create a report for the thrust created by the virtual disk:
    1. Right-click the Reports node and select New > Virtual Disk > Virtual Disk Force.
    2. Rename this report to Longitudinal Thrust.
    3. Select the Longitudinal Thrust report and set the following properties:
      Property Setting
      Virtual Disk Virtual Disk
      Force Component Option Z-Axis Force
  4. Create a report for the X component of the thrust created by the virtual disk:
    1. Right-click the Reports node and select New > User > Expression.
    2. Rename this report to X Component of Thrust.
    3. Select the X Component of Thrust report and set Definition to ${Longitudinal Thrust}*cos(abs(${Trim Down})).
  5. Create a report for the net force in the X direction:
    1. Right-click the Reports node and select New > User > Expression.
    2. Rename this report to X Component of Net Force.
    3. Select the X Component of Net Force report and set Definition to ${X Component of Thrust} - ${Drag}.
  6. Create monitors and a plot from the force reports:
    1. Within Reports, multi-select the Drag, X Component of Thrust, and X Component of Net Force reports.
    2. Right-click on any one of the selected items and select Create Monitor and Plot from Report.
    3. In the Create Plot From Reports... dialog, select Single Plot.
    4. Rename the Plots > Reports Plot node to Force Balance Plot.
    5. Select the Force Balance Plot node and set Title to Force Balance.
    6. Select the Force Balance Plot > Axes > Left Axis > Title node and set Title to Force Balance Plot.
  7. Monitor and plot the X component of the net force, and the amount of trim:
    1. Within Reports, multi-select the X Component of Net Force and Trim Down nodes.
    2. Right-click on any one of the selected items and select Create Monitor and Plot from Report.
    3. In the Create Plot From Reports... dialog, select Multiple Plots (one per report).
  8. To monitor the ship velocity in the X direction:
    1. Right-click the Reports node and select New > DFBI > 6-DOF Body Velocity.
      The Body property is automatically set to Ship, as that is the only 6-DOF body available.
    2. Rename the 6-DOF Body Velocity 1 node to Ship Velocity.
    3. Right-click the Ship Velocity node and select Create Monitor and Plot from Report.
  9. Save the simulation.