Estimating the Overall Erosion Rate

Create a field function and report to estimate the overall erosion rate.

To obtain an estimate of the erosion rate in g/hr for the whole restrictor, it is necessary to create a field function that multiplies the computed erosion rate in each boundary face by the face area.

To estimate the overall erosion rate:

Create the field function.
  1. Right-click the Automation > Field Functions node and select New > Scalar.
  2. Rename the User Field Function 1 node to Overall Erosion Rate.
  3. Edit the Dimensions property and set Mass to 1 and Time to -1 as shown.


  4. Click OK.
  5. Set the Function Name to OverallErosionRate.
  6. Edit the Definition property and enter the following definition in the dialog:

    $ErosionRate * mag($$Area)

  7. Click OK.

    The completed Properties window appears as shown below.



It is possible to report the overall erosion rate in units other than kg/s by creating a user-defined unit. This is demonstrated by creating a unit for g/hr. The conversion factor is:

1 g/hr = 2.777778 x 10-7 kg/s

  1. Right-click the Tools > Units node and select New > Units from the pop-up menu.


  2. Rename the Units 1 node to g/hr.
  3. Select the g/hr node and set Description to g/hr.
  4. Edit the Dimensions property and set Mass to 1.
  5. Set Time to -1.
  6. Click OK.
  7. Enter the Conversion property as 2.777778E-7.

    The completed Properties window is as shown below.



Create a report that uses the field function and unit:

  1. Right-click the Reports node and select New > User > Sum.
  2. Rename the Sum 1 node to Overall Erosion Rate.
  3. Set the Scalar Field Function to Overall Erosion Rate.
  4. Click the right half of the Parts property, expand Regions and Fluid nodes and select Restrictor.
  5. Set the Units to g/hr using the drop-down menu.

    The completed Properties window appears as shown below.



  6. Right-click the Overall Erosion Rate report node and select Run Report from the pop-up menu.

    See the Output window for the report result. A typical value is 1.858468e-01 g/hr .

The predicted quantity is for a quarter annulus only. To get the full erosion rate for the real case, it is necessary to multiply by 4. This gives a predicted erosion rate of 0.75 g/hr for the whole component.