# DBF Workshop Session 1 - Aerodynamic Study of Model Plane (Part 2)

## Link to part 1 of the tutorial:

DBF Workshop Session 1 - Aerodynamic Study of Model Plane (Part 1)

## Introduction

Welcome to the second part of the step-by-step tutorial for the simulation of a model airplane. In this part of the tutorial we will show you how to setup a simulation to investigate different angles of attack without changing the mesh.

## Simulation Setup for Different AOA

Now we will go through the setup of the simulation for the modified angle of attack. It doesn’t involve as many steps as before! We will just modify some of the boundary conditions.

### Duplicating a Simulation

Right click on your simulation, and click on Duplicate. This will create a copy of the simulation we just set up.

Rename your simulation to “H-Config - 20 deg” (optional) and click save.

### Boundary Conditions

In order to save time and computational capacity, we don’t want to use two different models and two different meshes to see the effects of a different angle of attack. So how do we change the angle of attack without changing the model? We can simply change the angle of incidence of the air, which will lead to a different angle of attack.

Here you can see that the AOA is the angle between the centerline and the flow direction. In this case, air is moving straight past the wing with no incidence angle, and as such the AOA is simply theta. This is the first simulation we did.

But here, the air has an angle of incidence beta, and as such, the AOA for this wing becomes theta + beta. This is exactly what we will do within the boundary conditions.

First, go to the boundary conditions, right click on Inlet and select Delete. Do the same for Outlet.

Next, go to the Sides boundary condition and remove all the faces except bundingBox3. This will remain as a normal slip wall.

Create a new boundary condition and rename it to “Inlet/Outlet” (optional).

Change the Type to Custom, and do the following:

1. Velocity: Inlet-outlet
a. x value: 0
b. y value: 5.847
c. z value: -19.126

Here we just defined that air is moving at 20 m/s with an angle of 17 degrees from the horizontal plane (this would be beta in the above diagrams). When you add it to the original angle of attack (theta = 3 degrees) you get AOA = 20 degrees.

1. Pressure: Set gradient to zero

2. Turbulent kinetic energy (k): Inlet-outlet
a. Inlet value: 0.06

3. Specific turbulence dissipation rate (omega): Inlet-outlet
a. Inlet value: 4.666

4. Select boundingBox1, boundingBox2, boundingBox5, and boundingBox6.

Click Save

### Lift & Drag

Wing CL

Now we’re going to adjust the result control items so that they match the new angle of attack/angle of incidence.

Go to Wing - CL

Under Type select Force and moment coefficients and change the following values:

1. Center of Rotation - should be the center of gravity of the object
a. x value: -0.511
b. y value: 0.081
c. z value: -0.122

2. Lift direction - the vector that describes the direction in which lift is acting (perpendicular to the flow direction).
a. x value: 0
b. y value: 0.95630476
c. z value: 0.2923717

3. Drag Direction - because we are concerned with lift in this result control item, don’t change anything for this setting

4. Pitch axis
a. Change the x value to 1

5. Freestream velocity
a. Change it to 20 which is the speed at which the plane is travelling

6. Reference length - this is the chord length of the wing
a. Change to 0.29

7. Reference area - this is the area that you projected to a plane parallel to the flow direction
a. Change to 0.27211108

8. Write control - this specifies how many times should this result be written to the solution. We don’t need it to be saved every step so change it to 50

Select the wing (solid_0_RightWing).

Click Save to save your changes.

Wing - CD

Now we will calculate the drag coefficient

Go to Wing - CD

Under Type select Force and moment coefficients and change the following values:

1. Center of Rotation - should be the center of gravity of the object
a. x value: -0.511
b. y value: 0.081
c. z value: -0.122

2. Lift direction - because we are concerned with drag in this result control item, don’t change anything for this setting

3. Drag Direction - the vector that describes the direction in which drag is acting.
a. x value: 0
b. y value: 0.2923717
c. z value: -0.95630476

4. Pitch axis
a. Change the x value to 1

5. Freestream velocity
a. Change it to 20 which is the speed at which the plane is travelling

6. Reference length - this is the chord length of the wing
a. Change to 0.29

7. Reference area - this is the area that you projected to a plane perpendicular to the flow direction
a. Change to 0.27211108

8. Write control - this specifies how many times should this result be written to the solution. We don’t need it to be saved every step so change it to 50

Select the wing (solid_0_RightWing).

Click Save to save your changes.

## Post-processing

When your simulation is completed, proceed to Post-Processor tab in order to post-process your results.

We will show the post-processing only for the first simulation results. You can then follow the same steps in order to post-process other configuration results

Once in Post-Processor, click on Solution fields under H-Config - 3 deg in order to load the results in the viewer. Due to fine mesh it can take a while to load the results in to the viewer.

Once the results have loaded, right click on Solution fields and select Add results to viewer - this will also take a while. The first set of results that loaded will be used only for the fluid, and this second set will be used for the surfaces of the plane.

Once the second set has loaded, under Mesh Regions select only the regions that correspond to the surfaces of the plane: solid_0_Body, solid_0_RightWing, and solid_0_Tail. You can select multiple entities using Ctrl + click.

Additionally, under Cell Arrays, select only the following variables: p, wallShearStress, and yPlus. These are the values of greatest interest directly on the surface of the wing.

Click Apply

Hide the fluid region by clicking on the small eye to the left of the the first results.

We will now start visualizing the results.

### Filters/Visualization

#### Slice

Make sure you click on the first set of results (so that it is highlighted in blue) and then click on Add Filter

From the list click on Slice

Once it has loaded, change the following:

1. Change Origin to -0.001, 0, 0

2. Uncheck Show Plane.

3. Click Apply to save the changes.

You can hide the airplane to get a better look at the slice.

Velocity

Change the Field to U [point-data] in order to see the velocity field. Zoom the results with the mouse roller and drag from middle mouse button to get a reasonable view. Turn on the color bar and drag it by holding mouse left button to the bottom.

#### Streamlines

Click on the small eye next to the slice to hide it. And do the same for the result with the surfaces in order to see the plane.

Make sure you click on the first set of results, select Add Filter and then select Stream tracer.

You are free to play around with the Center and Number of Points to get a visualization you like. You can also choose what field you want to visualize, and remember to turn on the color bar. For this case we used:

• Center: (-0.3, 0, -1)
• Number of points: 50
• Field: U [point-data]

#### Pressure Distribution on Plane

Hide the Stream Tracer by clicking on the eye to the left of it. And click on the second set of results (the one that has the surfaces)

Under Field select p [point-data]. This will show you the pressure distribution on the surface of the plane.

You can also select wallShearStress [point-data] and rescale it from 0 to 2. In this case you can see that there is no sign change so we are getting no flow separation.

### Screenshots & Saved States

Under the button View you can generate a screenshot from the viewer instead of having to screenshot your screen - this will get you a higher quality image.

And besides the Add filter button you can also select Save State which will save the filters you applied for later viewing. This means you don’t have to load everything from the start if you want to check your results again.

### Lift & Drag

Finally, the most important part of the results is analyzing lift and drag for the wing of the airplane.

In the Navigator on the left, expand Force coefficients plots and click on Wing - CL. SimScale calculates other coefficients, but in this case we are only interested in Lift Coefficient which for this model airplane is 0.3314

The formula for lift is:

Where:
rho is the density of the air = 1.1965 kg/m3
V is the velocity = 20 m/s
Aw is the reference area = 0.27211108 m2
CL is the Lift Coefficient = 0.3314

By plugging in the numbers we get that each wing produces 21.6 N of lift.

Now click on Wing - CD under Force coefficients plots and this time look at Drag Coefficient which is 0.03305

The formula for drag is:

Where:
rho is the density of the air = 1.1965 kg/m3
V is the velocity = 20 m/s
Aw is the reference area = 0.03840402 m2
CD is the Drag Coefficient = 0.03305

By plugging in the numbers we get that each wing produces 2.2 N of drag.

1 Like

Hi,
When I am adding the filters, the rendering is very laggy and the colours do not form properly. I am not sure if it is a problem with my laptop or the interface. The interface becomes extremely laggy when I am trying to rotate the geometry.

First of all sorry for the delayed response! Do you still have this issue or is everything fine now? If you need help please let me know

Best,

Jousef

No problem.
I still have the issue, but it improves when I switch rendering from remote to local.

I will continue working on local rendering for now.

Many thanks.

Alright @anarayan_das!

If it becomes too laggy again please contact me privately. We will figure out a solution to that! It is also hard to know what “laggy” means when I have no reference - so what seems to be slow for you could be smooth for me. If you have time and could create a small video/GIF that would be great!

Enjoy the workshop and happy SimScaling!

Jousef

Hello, I have uploaded my assignment yet I did not receive any confirmation, e.g. via email. Is it ok?

Hi @Olin!

Usually everybody who hands in his assignment will receive a confirmation email. @AnnaFless, any input from your side?

Best,

Jousef

Hi,
I added all the filters shown in step by step tutorial and saved state next to the filter button.
But after loading my project some hours later I cannot find the saved state and all the filter I applied has disappeared.
Is there some other buttons from where I have to load my saved state.

Next question:
(image of quarter Sun) button that enable local rendering.
If I downloaded my results and enabled local rendering then will my laptop be used for viewing the results thus removing all the lags when you view the results in remote configuration.
I had to go through a lot of lags when panning,zooming my results I want know if this solves my problem.

Thank you.

I have tried to upload my link several times. Every time it shows the sign that my assignment was uploaded successfully, but that is it. No email, no confirmation at all. Please check it out. Thank you a lot.

1 Like

Hi @Aabhushan!

Have you tried to save the state again? Try it with a simple filter first and see if it still ignores your settings. Feel free to share the project with us so that we can have a more detailed look at it.

Downloading the results is useful when you want to have the full benefit of the offline post-processing power of Paraview but is not related at all to the performance of the platform. Are you able to generate a GIF and share it with us? That would be great.

All the best!

Jousef

Hi, i didn’t know that it was possible to run 2 simulations at the same time. I had time to do this Homework only this weekend and as I had some difficulties to learn it, I don’t think it will be finished until 11:59. Both my simulation are running now and it will be finished only after 11:59. Can I submit them after the time? Initially I thought that I could simulate a case only after the previous was finished, so it delayed all the work until I got know I could run some cases simultaneously.

That should be fine @skfelix! No worries there

All the best!

Jousef

1 Like

Hi Jousefm,
I am wondering if that is okay for submitting a later time.
Sorry for that & Got a quite busy period.

Sure @czhang!

Cheers!

Jousef

Hi @Olin,

Cheers,
Anna

Hi, I have submitted my homework just now, I do apologize for late submission but we had our semester exams going on for the past week so I couldn’t submit or work on it earlier. I hope you accept the late submission. _

1 Like

Anna, I submitted my HW several weeks ago , however I never got a confirmation email. I copy pasted the link from the dashboard into the homework link field as per the new instructions.

Hi @akpcorp!

If you have seen the message that you successfully submitted the homework, everything is okay. As far as I know there has not been a separate email sent out for this workshop. More information will be given by my colleague @AnnaFless.

Cheers!

Jousef

I still haven’t gotten a response to my issue of hw 1&2 submissions.

Thanks!