3d Shape with lowest drag coefficient subsonic ground level

In summary, for a motorcycle with dimensions of 60cm width (at 45%), 120cm height (at 45%), and 220cm length, a teardrop shape with a truncated tail would likely have the lowest drag coefficient at ground level and subsonic speeds (0-150kph). However, the naca 0021 airfoil may also be a good choice, with a fineness ratio of 3:1 in the air and 5:1 on the ground. Stretching the naca 0021 airfoil to meet the required dimensions may be difficult and its drag coefficient cannot be tested. It is also unknown if there is a shape better than the naca 0021 for achieving speeds
  • #1
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Hello,

What shape has the lowest drag coefficient at ground level and at subsonic speeds (0-150kph) with the following dimensions?

Width 60cm (at 45%)
Height 120cm (at 45%)
Length 220cm

These dimensions will fit my motorcycle (not too narrow and not too long).

I am thinking it would be a symmetrical airfoil with a truncated tail but I do not know for sure. That is why I am asking.

The shape will have 10-20cm ground clearance.

Thank you for your time, this stuff is way over my head.
 
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  • #2
A teardrop shape would likely be pretty close to ideal. Truncating the tail would likely increase drag.
 
  • #3
I'd have to agree with you there.

I have been looking at airfoiltools.com.

Stretching the naca 0021 airofoil to 128.7% gives the required 60cm thickness with a 220cm chord. However the widest point is at 30% length not 45% length. It is impossible to change this. Also the changed airfoil cannot be tested to determine it's drag coefficient.

The same naca0021 airfoil would be stretched vertically to double the thickness to reach the required height of 120cm. However this is impossible to create and impossible to test.

Considering that a naca0021 airfoil with a fineness ratio of 3:1 is perfect in the air and 5:1 ratio on the ground I definitely want to get as close to the latter ratio.

Using the perfect shape of the naca 0021 airfoil I should be able to achieve sub 0.1 drag coefficient and reach speeds of around 200kph at 10kw.

It is unknown if there is a shape better than the naca 0021.
 

1. What is a 3D shape with the lowest drag coefficient?

A 3D shape with the lowest drag coefficient is a shape that produces the least amount of resistance to airflow when moving through a fluid, such as air. This is important for minimizing drag, which can slow down and impede the movement of an object.

2. How is the drag coefficient of a 3D shape determined?

The drag coefficient of a 3D shape is determined by conducting experiments in a wind tunnel or through computational fluid dynamics (CFD) simulations. These methods measure the forces acting on the shape and calculate the drag coefficient based on the shape's characteristics and the fluid properties.

3. What is the significance of having a low drag coefficient for a subsonic ground level object?

A low drag coefficient is significant for a subsonic ground level object because it means that the object will experience less resistance and therefore require less energy to move. This can result in improved fuel efficiency and increased speed for vehicles or other objects.

4. What factors affect the drag coefficient of a 3D shape?

The drag coefficient of a 3D shape can be affected by various factors such as the shape's geometry, surface roughness, speed, and the properties of the fluid it is moving through. For example, a streamlined shape with a smooth surface will have a lower drag coefficient compared to a shape with sharp edges and a rough surface.

5. How can the lowest drag coefficient be achieved for a 3D shape at ground level?

To achieve the lowest drag coefficient for a 3D shape at ground level, it is important to consider the shape's design and surface properties. This can include streamlining the shape, reducing surface roughness, and optimizing the shape's dimensions. Using wind tunnel testing or CFD simulations can also help in identifying the most efficient shape for minimizing drag at ground level.

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