Laminar Flow Airfoils
 

I understand that laminar-flow foils didn't work in the past because, but I have heard more recently about development in laminar flow technology on airfoils.

Do they actually produce as smooth a flow as the laminar-flow-control concepts which use boundary layer suction through small holes in the leading edge, or the leading-edge and upper wing?

Not so much what you hear Jay as what you read and understand.
There is no agreement on what produces lift on a wing anyway so how can we begin to unravel this question?

They work very well in high-performance gliders.

regards,
HN39

....which only fly on weekends and are kept highly polished in a closed container for 99% of their life on earth!

Laminar flow aerofoils work well on most jet aircraft. The design problem is, how much does it cost to have a wing with even more laminar flow? The nature of air is that it prefers not to adhere to the rear section of a wing (or any surface) aft of maximum thickness unless the designer gives it some encouragement. Shape it the vital feature used in most designs. Anything else requires complex engineering and/or large amounts a energy to run. A glider pilot can justify the cost of increased laminar airflow but an airline operator will have to stick to the 40% or so they get as standard. Currently, there is unlikely to be an economic payback if more of the wing remains laminar. But if the price of fuel continues to increase, that may well change.

PM

You can even clean the wings while flying, e.g. YouTube - Bugwiping during flight

Okay, to rephrase the question

1.) What is the L/D ratio of a DC-8 wing, and what percentage of the flow is laminar?

2.) What kind of percentage of the flow is laminar, theoretically speaking, on a plane that used small holes on the wing (including leading edges) with pumps to suck away the turbulent flow and artificially establish laminar flow at:
- Mach 0.8
- Mach 0.9
- Mach 2.0
- Mach 3.0


3.) What kind of percentage of the flow, hypothetically is laminar on a laminar-flow airfoil (one that does not use suction and small holes) designed for:
- Mach 0.8
- Mach 0.9
- Mach 2.0
- Mach 3.0

Robyn
 

Robyn may I suggest something here please. Multiple choice answers to questions here in the UK, began with the GED (Aged 16 yrs first formal exam) Physics paper around 1969 to 1971. It was pioneered by the Nuffield Science foundation and really made good ground in physics education.

It was found that a maximum of four variables worked well to assess the ability of the student. When more options were added the results became worthless. So in this light I would be most grateful if you could limit the options to four.

It is best not to ask for two variables in one question. So if you have one fixed, then give the possible answers in the options you will get more replies. So really asking a question that depends on, or is premised on, a question is counter productive and makes the concept more complicated than it really is.


Hope this helps.
Regards

P.S The big intake fans on the jet engines have some really wonderful BLADE profiles..far more interesting than wing profiles.

DERG

Understood, I edited the previous post to reflect 4 variables.

I've never seen any fan-blade profiles used on modern commercial jets. Looking at the tips though it almost looks like they have some inverse camber (which wouldn't be surprising as at high RPM you tend to get supersonic velocities and inverse camber is well suited for supersonic airflow).

Robyn

If you go onto the GE website they have some really nice pics of those blades on the front fan. GENx I think they call the new one. They really are stunningly beautiful. In my view nature inherently seeks the form that is beautiful. Do you agree? For instance the A380 is not good looking.