Analyze the Results

Create a display group to view the surface of the drone. Next, create sensors and formulas to display and calculate important design factors. Finally, generate a streamline plot to see how the drone's design disperses airflow.

A display group is a combination of items and methods to control model visibility. By controlling the visibility of your model, it becomes easier to see and analyze the results of your simulation. You can also use analysis tools, such as sensors, formulas, and plots, to display and calculate pertinent quantities and to visualize your results. Use these results to evaluate the quality of your design with respect to a particular parameter, such as force, and make improvements.

In this example, you isolate the display of the drone's surface. Next, you use symmetry to visualize the entire surface of the drone. Then, you create two sensors to display the drag and lift forces, and you create two formulas to calculate the corresponding drag and lift coefficients. Finally, you create a streamline contour plot to view the movement of airflow around the drone. This information can be used to pinpoint areas of the drone that can be redesigned to optimize the forces acting on the drone.

This task shows you how to:

Create a Display Group

  1. From the Results section of the Assistant, click Display Group .
  2. Select Entities from the Item section, and then select Surfaces from the Method section.
    A list of all surfaces from the model appears in the Selection section.
  3. Select Drone Surface from the options in the Selection section, and click Replace selected .

    Tip: You can click Restore all to see the original display.

    The fluid domain is replaced by the surface of the drone that is contained within the fluid domain. The color scheme on the drone's surface depends on the active plot selection in the Plots window. For example, a plot of the gauge pressure is shown below.

  4. In the Display Groups dialog box, click Create new display group .
  5. Name the display group Drone Surface, and click OK.
  6. Click Close.

Visualize the Entire Drone

  1. From the Display section of the action bar, click Result Options .
  2. Click Model symmetry , and select Model symmetry.
  3. From the Mirror section, clear all mirror planes and select only XZ.
    The 3D area mirrors the display group you previously created, allowing you to visualize the results for the entire drone.

  4. Click Close.

Create Sensors for the Drag and Lift Forces

  1. Create a sensor to display the last converged drag force value.
    1. From the Sensors section of the action bar, click Sensor .
    2. From the Type options, select History.

      A history-based sensor allows you to display data collected by the history output request. You created the history output request earlier to gather information about the total fluid force against the portion of the drone inside the fluid domain.

    3. Name the sensor Drag Force.
    4. From the Values section, select FORCE from the Variable options.
    5. From the Quantity options, select Vector Component 1.

      Vector Component 1 corresponds to the X-axis, which is the direction of airflow and, therefore, the direction associated with the drag force.

    6. From the Parameters section, clear all selections, and select only Last.
      The sensor will display the force from the last iteration only.
    7. Click OK.
  2. Similarly, create a sensor named Lift Force to display the last converged lift force value.

    Tip: Vector Component 3 corresponds to the Z-axis, which is the direction that is vertical with respect to the drone and, therefore, the direction associated with the lift force.

  3. From the tree, expand Result > Result Of Flow Analysis Case.1 > Sensors to find the two new sensors you created and their values.
    For the portion of the drone inside the fluid domain, the corresponding drag and lift forces are approximately −14 N and 108 N, respectively. You can double these values to determine the drag and lift forces for the entire drone. You can also use these values to determine if the drone's design meets its requirements.

Calculate the Drag and Lift Coefficients

  1. From the Tools section of the action bar, click Formula .
  2. In the Formulas: Result Manager dialog box, create the parameters required to calculate the drag and lift coefficients.
    1. Create a parameter for the air density by double-clicking the text field to the right of New Parameter of type and double-clicking Density from the list.
    2. Click New Parameter of type.
      The Result Manager creates a single-value parameter with units of density and displays it in the table.
    3. Edit the name and value of the parameter to Air Density and 1.205kg_m3, respectively, and click Apply.
    4. Similarly, create a parameter named Air Velocity with units of velocity and a value of 22.352m_s.
    5. Create a parameter named Projected Area for Drag with units of area and a value of 0.327m2.

      Tip: If you have the appropriate role, you can calculate the projected area using the Generative Shape Design app.

    6. Create a parameter named Projected Area for Lift with units of area and a value of 1.733m2.
  3. Create drag and lift coefficient parameters with no assigned value.

    Note: For dimensionless parameters, select Real as the unit type.

  4. Select 'Drag Coefficient' from the table, and click Add Formula to assign a formula to the drag coefficient parameter.
    The Formulas: Result Manager dialog box closes, and the Formula Editor dialog box opens.
  5. Search the Dictionary for Parameters and Operators, and double-click items you need to add to recreate the equation for the drag coefficient.

    For more information about the equation (that is, C ⁢ =   2 F A ρ v 2 ), see the Problem Description.

    The formula reads as follows: 2 * `Result Of Flow Analysis Case.1\Drag Force\Last` / (`Projected Area for Drag` * `Air Density` * `Air Velocity` ** 2).
  6. Click OK.
  7. Similarly, select 'Lift Coefficient' from the table, and recreate the equation for the lift coefficient.
  8. Click OK to close the Formula Editor dialog box and to close the Formulas: Result Manager dialog box.
  9. From the tree, expand Result > Parameters to find the drag and lift coefficients you created and their values.

    You calculated the drag and lift coefficients using parameters that consider a half-symmetry model. In cases where a full model value is required, you may need to double half-symmetry parameters before you create these formulas.

    If you rerun the simulation with some variations to the scenario, you will see the results of the drag and lift coefficients immediately after the simulation completes.

    The drag and lift coefficients are approximately −0.14 and 0.21, respectively. You can use these values to determine if the drone's design meets its requirements.

Generate Streamline Contours

  1. In the 3D area, right-click the background and select Ambience > Dark Review to improve visibility.
  2. Add streamlines to illustrate the airflow around the drone.
    1. From the Results section of the Assistant, click Streamlines .
    2. From the Seed support options, select Rake.
    3. Specify the Rake start and Rake end coordinates by using the pointers to click two points on the drone's surface.
      Tip: Click a point near the wing tip and a point on the drone's body.

      Blue dots appear between the Rake start and Rake end. These dots indicate the spacing of the tines.



    4. Specify 20 in the Tines box.
    5. Click OK.
      The streamlines display the pressure of the air as it flows around the drone. Since the mesh you applied earlier is relatively coarse, the tines appear somewhat linear. If you refine the mesh, you are likely to accentuate the curvature of the streamlines, so it is more representative of the recirculation pattern in the wake area. You can experiment with the mesh refinement and streamline contours to witness this phenomenon.

  3. In the Plots window, expand the Plot options and select Velocity.1 to display the velocity of the air as it flows around the drone.


  4. Save your work.

Congratulations, you have successfully completed this example!