Monitoring and Plotting Resistance Data

The resistance of a ship hull is defined as the force required to tow the ship in calm water at a constant velocity. Generally, a ship is designed to move through the water with as little force as possible. You can create a graph of the hull resistance over time to extract the value of this design parameter of your ship from the simulation. The drag force can be split into the two components: pressure drag and shear drag.

To analyze the drag of the ship hull:

  1. Create a report for the shear drag over time:
    1. Right-click the Reports node and select New > Flow / Energy > Force.
    2. Rename Force 1 as DragShear.
    3. In the DragShear - Properties window:
      • Set Force Option to Shear.
      • Set Parts to Regions > Virtual Towing Tank > Boundaries [all boundaries with the prefix KCS_Geometry] and click OK.
      • Set Direction to [-1.0, 0.0, 0.0].
  2. Create a report for the pressure drag over time:
    1. Copy and paste the DragShear node.
    2. Rename DragShear Copy as DragPressure.
    3. In the DragPressure - Properties window, set Force Option to Pressure.
  3. Create a report for the total drag over time:
    1. Copy and paste the DragShear node.
    2. Rename DragShear Copy as DragTotal.
    3. In the DragTotal - Properties window, set Force Option to Pressure + Shear.

  4. Create a monitor and plot for a combined display of shear and pressure drag:
    1. Multi-select DragPressure and DragShear.
    2. Right-click on any of the highlighted nodes and select Create Monitor and Plot from Report.
    3. In the pop-up window, click Single Plot.
    4. Rename Plots > Reports Plot as ShearAndPressureDrag Plot.
    5. Right-click the Plots > ShearAndPressureDrag Plot node and select Open.
  5. Create a monitor and plot for the total drag:
    1. Right-click the Reports > DragTotal node and select Create Monitor and Plot from Report.
    2. Rename Plots > DragTotal Monitor Plot as DragTotal Plot.
    3. Right-click the Plots > DragTotal Plot node and select Open.
In a later stage of this tutorial, you compare the predicted drag coefficient with an experimental value. You can obtain a mean value for the drag force using a statistics monitor.
  1. To compute the mean drag force:
    1. Right-click the Reports node and select New > User > Statistics Report.
    2. Rename the report node to Mean Total Drag.
    3. Edit the Mean Total Drag node and set the following properties:
      Property Value
      Statistic Mean
      Sample collection policy Last N Samples
      Monitor DragTotal Monitor
      Last N Samples > Sample Count 10