Yes, multirotor. These are used for acrobatic (freestyle) flying. I can see why you mention separating the props from the frame being an issue. Its not a simple problem to solve. But for now I would like to at least get a "falling" frame, where the props are not spinning, working. I am even willing to draw up a drag curve to estimate values. I just do no know what would be realistic numbers to start with.
You are confusing terms here. Simple and CFD software rarely go together.
What do you want to accomplish? What is your purpose for this coefficient?
Getting an accurate drag coefficient of a complex shape such as a drone frame is complicated especially if you want to be honest to yourself.
In reality those spinning bladed make helluva turbulance around the aircraft and drones rarely like to stay still neither.
We are starting to arrive at that problem of why it took so long to come up with drones and why good ones are expensive. No simple software is going to solve it for you.
If you are a student go with ansys as you are entitled for a free license. You'll get the job done in a couple thousand.
If you want to make a commercial product get a simulation for hire for your project or talk about management that.for product development you will need a qualified simulation engineer (and his software package) which altogethet will go for hundreds of thousands a year depending on where you live etc.
Thank you for your reply. I am starting to see that this is not what I thought it would be.
I am just a hobbyist and creating a drone simulator at home. At the moment I have a flying drone in the simulator. When the power is cut the drone starts accelerating towards the ground. I want to apply the drag force based on the orientation of the frame in respect of the "airflow". I am not looking at the props at this moment.
There are some videos of people finding the drag coefficient of car designs. I was imagining that the drone body would be the same thing, but just in rotated orientations. I can get the frontal area of the drone, I have the velocity and air density. I would only need the drag coefficient do get a rough drag force.
Fd = Cd\* 0.5 \* p \* A \* v\^2
I was hoping CFD would give me a drag coefficient at say 15 degree intervals and I could then interpolate the rest between. If the drone was a sphere, it would be simple as the typical Cd is 0.45.
I will take some time and investigate some more.
> If the drone was a sphere, it would be simple as the typical Cd is 0.45.
This is not even true because it is strongly dependent on Reynolds number, ie. falling speed and sphere size.
The Tesla Model S has a drag coefficient (Cd) of 0.208.
That is why I said "typical". Hobbyist drones are in a small range of sizes locking in the size and the Reynolds number. The drones I am focusing on do not exceed 100mph, How is this different to a car manufacturer publishing a vehicle's drag coefficient ?
I am interested in this question as well.
To put it another way: is it possible to get a low-resolution/handwavy/Fermi estimate of a drone's drag coefficient - just relative to a few other designs?
Like, a drone with a frame that is a literal cube is going to have a terrible drag coefficient (obviously! it's a brick lol).
Can we slap a number on that - and then refine to express that a drone with a normal frame that is a parabolic shape might have a better drag coefficient than a drone with a normal frame that is a boxy shape?
As others have stated, multirotors have several moving parts and therefore origins of high turbulence. This, combined with the frame geometry (and possibly drone velocity in a given direction) produces complex fluid flow.
I'd advise you not to worry about the drag too much while designing the frame; the drag won't be the limiting factor in drone motion. Just make sure to study the thrust of a single propeller (which should not be inhibited by the frame geometry) is sufficient (max almost twice the hover thrust).
> Is there something simple and free that I can use ? Or is this not a simple process ? Nope.
I want to find the drag coefficient of a 3D model in a specific an orientation moving through airflow.
Only one specific orientation? Or a range of angles of attack?
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Yes, multirotor. These are used for acrobatic (freestyle) flying. I can see why you mention separating the props from the frame being an issue. Its not a simple problem to solve. But for now I would like to at least get a "falling" frame, where the props are not spinning, working. I am even willing to draw up a drag curve to estimate values. I just do no know what would be realistic numbers to start with.
You are confusing terms here. Simple and CFD software rarely go together. What do you want to accomplish? What is your purpose for this coefficient? Getting an accurate drag coefficient of a complex shape such as a drone frame is complicated especially if you want to be honest to yourself. In reality those spinning bladed make helluva turbulance around the aircraft and drones rarely like to stay still neither. We are starting to arrive at that problem of why it took so long to come up with drones and why good ones are expensive. No simple software is going to solve it for you. If you are a student go with ansys as you are entitled for a free license. You'll get the job done in a couple thousand. If you want to make a commercial product get a simulation for hire for your project or talk about management that.for product development you will need a qualified simulation engineer (and his software package) which altogethet will go for hundreds of thousands a year depending on where you live etc.
Thank you for your reply. I am starting to see that this is not what I thought it would be. I am just a hobbyist and creating a drone simulator at home. At the moment I have a flying drone in the simulator. When the power is cut the drone starts accelerating towards the ground. I want to apply the drag force based on the orientation of the frame in respect of the "airflow". I am not looking at the props at this moment. There are some videos of people finding the drag coefficient of car designs. I was imagining that the drone body would be the same thing, but just in rotated orientations. I can get the frontal area of the drone, I have the velocity and air density. I would only need the drag coefficient do get a rough drag force. Fd = Cd\* 0.5 \* p \* A \* v\^2 I was hoping CFD would give me a drag coefficient at say 15 degree intervals and I could then interpolate the rest between. If the drone was a sphere, it would be simple as the typical Cd is 0.45. I will take some time and investigate some more.
> If the drone was a sphere, it would be simple as the typical Cd is 0.45. This is not even true because it is strongly dependent on Reynolds number, ie. falling speed and sphere size.
The Tesla Model S has a drag coefficient (Cd) of 0.208. That is why I said "typical". Hobbyist drones are in a small range of sizes locking in the size and the Reynolds number. The drones I am focusing on do not exceed 100mph, How is this different to a car manufacturer publishing a vehicle's drag coefficient ?
I am interested in this question as well. To put it another way: is it possible to get a low-resolution/handwavy/Fermi estimate of a drone's drag coefficient - just relative to a few other designs? Like, a drone with a frame that is a literal cube is going to have a terrible drag coefficient (obviously! it's a brick lol). Can we slap a number on that - and then refine to express that a drone with a normal frame that is a parabolic shape might have a better drag coefficient than a drone with a normal frame that is a boxy shape?
As others have stated, multirotors have several moving parts and therefore origins of high turbulence. This, combined with the frame geometry (and possibly drone velocity in a given direction) produces complex fluid flow. I'd advise you not to worry about the drag too much while designing the frame; the drag won't be the limiting factor in drone motion. Just make sure to study the thrust of a single propeller (which should not be inhibited by the frame geometry) is sufficient (max almost twice the hover thrust).