Aerodynamic question
Discussion
Afternoon. I'm doing a design, but aerodynamics are not my specialism so could use some advice, please. Using this image to demonstrate:
To reduce drag, assuming airflow from the left, am I better with a smaller frontal area (~50%, profile 1) or more of a taper to give "streamlining" (profile 2)? As a side note, a colleague has claimed that a profile similar to 3 will improve things, but I'm not convinced: wouldn't it give a larger frontal area and a larger recirculation zone behind the bulbous section, further increasing drag?
Many thanks in advance.
To reduce drag, assuming airflow from the left, am I better with a smaller frontal area (~50%, profile 1) or more of a taper to give "streamlining" (profile 2)? As a side note, a colleague has claimed that a profile similar to 3 will improve things, but I'm not convinced: wouldn't it give a larger frontal area and a larger recirculation zone behind the bulbous section, further increasing drag?
Many thanks in advance.
In order of drag, low to high, from a non qualified wally on the www
1, 2, 3.
For me the order of 2 and 3 depends on air speed. 2 would be better at higher speeds and 3 better at lower speeds. I think 1 will always offer the lowest drag, just due to reduced frontal area.
1, 2, 3.
For me the order of 2 and 3 depends on air speed. 2 would be better at higher speeds and 3 better at lower speeds. I think 1 will always offer the lowest drag, just due to reduced frontal area.
Edited by Kawasicki on Monday 21st December 13:18
Kawasicki said:
In order of drag, low to high, from a non qualified wally on the www
1, 2, 3.
For me the order of 2 and 3 depends on air speed. 2 would be better at higher speeds and 3 better at lower speeds. I think 1 will always offer the lowest drag, just due to reduced frontal area.
That was my thought, but I've seen a lot about tapering, particularly in aircraft and automotive.1, 2, 3.
For me the order of 2 and 3 depends on air speed. 2 would be better at higher speeds and 3 better at lower speeds. I think 1 will always offer the lowest drag, just due to reduced frontal area.
Edited by Kawasicki on Monday 21st December 13:18
McAndy said:
That was my thought, but I've seen a lot about tapering, particularly in aircraft and automotive.
Have a lookhttp://s1271.photobucket.com/user/aerohead2/media/...
This app will allow you to test custom shapes in a virtual wind tunnel.
http://aerodoodle.swan.ac.uk/
http://aerodoodle.swan.ac.uk/
Kawasicki said:
Thanks. Parallel sided looks good, then!Tapering helps by reducing turbulence behind the object, however all 3 of your shapes look to have the same rear area, the taper will help reduce the turbulence a bit because the flow is already directed inwards slightly at the rear of the body, but probably not enough to offset the increased frontal area. Tapering to a point at the rear would reduce the drag further, but it will also be dependant on the speed, take a look at Reynolds Number id you're not familiar with it, which related flow speed and a reference length to the drag characteristics.
However... depending on what you're trying to achieve, I would expect a scaled down version of 3 to be able to provide lower drag for a given structural strength.
It's a long time ago I last did any aerodynamics though.
However... depending on what you're trying to achieve, I would expect a scaled down version of 3 to be able to provide lower drag for a given structural strength.
It's a long time ago I last did any aerodynamics though.
I require a flat surface on the right, so the "Kamm" tail needs to stay. The length over which the profile sits is ~85 mm at present, with a parallel sided option having a nose of ~Ø20 mm and the bulbous/tapered ~Ø40 mm. Having not done any maths, I'm beginning to err towards a Ø25 mm nose with a small taper. I'm sure that there used to be a Java applet somewhere that quickly calculated Cd!
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