The objective of this simulation is to analyze how the drag reduction system
on a Formula 1 car affects the airflow to reduce drag.
Open a new session of Discovery.
Close the Welcome screen and then browse for the file Rear Wing DRS.dsco.
Modern Formula 1 cars use the Drag Reduction System or DRS to reach a higher top speed
and overtake the cars in front of them.
This system changes the angle of the upper part of the rear wing of the car.
With the drag greatly reduced, the car can move faster.
To begin this exercise, click External Flow from the Simulation toolbar.
Zoom out until the enclosure preview outline is fully visible.
The airflow over the wing will be moving from right to left,
so let’s click the green arrow on the right side of the enclosure preview
to define the inlet face.
Click the bottom face of the enclosure to define the ground plane.
With these 2 items defined, the fluid enclosure gets created and the simulation could be started.
Press H on the keyboard to return to the Home view.
Examine the boundary conditions in the Physics tree on the left side of the window.
It looks like we need to make a few adjustments to our operating conditions.
The fluid material for the simulation is set to liquid water by default,
but we should be using air.
Right click the Water (Liquid) entry and select Edit.
A new menu will appear on the right side of the HUD.
Open the drop-down menu next to Water and change the fluid material to Air.
Press S on the keyboard to exit the Material assignment function,
then click anywhere in the background.
The top speed of an F1 car is over 300 km per hour,
so the airflow in our simulation needs to accurately reflect this.
Click the value of the velocity next to the Flow Inlet entry and increase it to 85 m/s
and press Enter.
That’s about 306 km per hour.
The last adjustment we will make is to apply a free slip condition to the Ground Plane.
Right click the Ground Plane entry in the Physics tree and select Edit,
then click the Free Slip option on the right side of the HUD.
Press S on the keyboard and click anywhere in the background to exit the menu
and deselect the faces.
Press Z on the keyboard to zoom out to the model extents.
Let's start the simulation to see how the results look.
Locate the green Solve button in the bottom right corner of the window and click it.
The simulation will begin running.
While Discovery is performing calculations, a white indicator will travel around the hexagon.
Once the simulation has finished, the hexagon will be solid green and we can examine our results.
Let's go to the Model Tree at the top left of the window
and locate the Enclosure in the list of components.
You may need to expand the entry for the model to locate it.
Select the Hide/Unhide icon to hide the enclosure.
The default display style for the results is streamlines.
Let’s turn the streamlines off for now by clicking the Streamlines button.
Show the Contours by clicking the appropriate button in the results panel.
Hover the mouse cursor over the Contours button to access the options
and set the Surface Display Priority to Outer.
Next, click the Cut Plane button to get a better view of the airflow
around the rear wing.
If necessary, the cut plane orientation can be changed by selecting the plane
and double clicking the red rotation handle.
Press S on the keyboard to exit any active tools.
Click the Y axis on the orientation tool to align the view with the screen.
The end plate on the wing is blocking our view of the airflow
passing over the wing elements.
Right click the Cut Plane and select Clip with Plane > Clip
to get a better visualization of the airflow, then zoom in.
As the designers and engineers performing these simulations,
it's up to us to make sure that they're as realistic as possible,
otherwise the results that we generate may not be accurate.
Once the simulation finishes running, we can examine the results.
Can you identify any problems?
As you may have noticed, the airflow seems to be passing through a portion of this upper wing segment.
As we've learned in a previous video, there are some models where it will be necessary
to increase the fidelity to get more accurate results.
The default fidelity value on this machine is 17.52 mm.
Depending on your machine, the range of values along the fidelity bar can vary.
Try to match the fidelity value we show in the video to the best of your ability.
Let’s improve the resolution of the wing geometry.
Let’s start by pausing the simulation and increasing the fidelity to the maximum value.
After increasing the fidelity to the maximum setting, the value is 10.83 mm.
We can adjust the distance between the enclosure boundaries and the model.
This is ok for the scope of this exercise.
Disable the results display, then unhide the Enclosure from the Model Tree.
Start the Pull tool from the Design tab and click the top face of the enclosure.
Using the Ruler option, adjust the position of the top face
so the total height is 1400 mm.
Use the bottom face of the enclosure as the baseline for the dimension.
Then select the left face and specify an offset of 395 mm from the end plate with the Ansys logo.
Repeat this process for the opposite face.
Finally, select the outlet face and use the Ruler option to specify an offset of 2700 mm to the Inlet.
Press Esc on the keyboard and click anywhere in the background to exit the Pull tool
and deselect the faces.
Return to the Model Tree and hide the enclosure again.
Restart the simulation to see the updated fidelity value.
On our machine adjusting the enclosure size has improved the fidelity to about 9 mm.
Enable the Contours display again.
Let’s check the drag force on the model by creating a monitor.
Click the Monitors button in the Simulation tab.
Expand the “Select a Variable...” drop-down menu and click Force.
Click and drag a box around the entire model.
The quantity we’re interested in determining is the drag force.
Using the orientation tool as a reference,
we can see that this force will act in the negative X direction.
Ensure that X is selected from the menu on the right side of the HUD
and click the green check mark,
The monitor will display automatically.
Right click “X Force 1” from the monitors list in the top righthand corner of the window
and select Rename.
Let’s call this monitor Drag.
Then, click anywhere in the background to deselect the model.
The Monitor creation tool should remain open.
Let’s define one more monitor to calculate the downforce acting on the rear wing.
Click and drag a box around the model again.
The downforce acts in the negative Z direction,
so click Z from the menu on the right side of the HUD,
and click the green check mark.
Click anywhere in the background and press S on the keyboard to exit the Monitors tool.
Rename the second monitor “Downforce”.
Once the simulation converges, the monitors will automatically display the results.
The corresponding values will also be listed in the table in the top right corner.
Remember that the forces are acting in the opposite direction of their respective axes,
and thus the reported values are negative.
Let's look at the results with streamlines enabled.
Remember to disable the Contours as well.
We can make some adjustments to the streamline emitter to get a better view.
Rotate the model to see the entire emitter, then click the emitter boundary
and adjust the shape and size
so the streamlines are concentrated in the center of the rear wing.
Notice the large empty space behind the wing elements.
If we disable the streamlines and switch to the Contours with the cut plane enabled,
we can see a large area of slow-moving blue air.
This is caused by flow recirculation behind the wing elements.
Change the result display to Static Pressure.
Disable the Cut Plane and change the Contours Surface Display Priority to Inner.
In the Model tree, hide the Lower Wing, DRS, and the End Plates.
Looking at the results now we can see the front of the wing is red,
indicating areas of high pressure.
Rotating the model, we can see areas of much lower pressure on the back.
These low-pressure areas create a suction effect.
Unhide the 4 solid bodies of the rear wing.
Change the Result Display back to Velocity and the Contours Surface Display Priority
to Outer,
then Disable the Contours and enable Streamlines.
The Drag Reduction System, or DRS, is activated by rotating the top wing to reduce its obstruction
of the incoming air and decrease the drag,
thereby increasing the top speed of the car and providing an advantage when passing a
competitor's car in front.
Let's activate the DRS now and examine the values for downforce and drag.
To do this, expand the Advanced Selection menu in the bottom right corner of the window
and click the driving dimension labeled DRS Angle.
This has been predefined to allow us to rotate the top wing by entering a value.
Type in a value of negative 45 degrees, then press Enter.
As we can see, the top wing has rotated
and there's a much larger gap between the two wings now.
If necessary, restart the simulation by clicking the Solve button again
and allow the simulation to converge.
Notice that both the down force and the drag values have dropped substantially.
Examine the streamlines.
The new position of the upper wing reduces its resistance to the incoming air,
streamlining the flow behind the two wings.
Almost no recirculation is detected there.
This can also be seen in the velocity contours.
Let's change the result display to Pressure.
Disable the streamlines, enable Contours
and set the Surface Display Priority to Inner once again.
Examine the pressure contours.
Notice that the bottom wing, which remains in its fixed position,
has a higher pressure on the top face, compared to the top wing in the open position.
Looking at the underside of both wings,
we can see a low-pressure area on the underside of the bottom wing,
while for the top wing the pressure reduction is milder.
This concludes the demonstration on analyzing the decrease in drag produced by a change
to the geometry of an F1 rear wing.