How calculate lift/drag using static pressure taps in wind tunnel test?

[Jurgen M]

An airfoil section in a wind tunnel has many static ports/holes/taps on its upper and lower surface. These static ports can only read static pressure which acts perpendicularly to the local airfoil surface.

In place A are static ports that read a pressure value of relative -100 Pa . This pressure acts perpendicularly to the airfoil surface, so it is not perpendicular to the wind / x horizontal co-ordinate. Do we need to convert only this vertical component when we put this value in a diagram when we draw the pressure distribution? The pressure in place A has a vertical component (lift) and also a horizontal component (thrust) ... So how would the integral "know" in which direction the pressure acts?

Can you please explain with an example from start (pressure measurement) to end (calculated lift/drag) how this procedure looks like? (Are the experimentally measured pressures at static ports given in relative or absolute pressure?)

 

[Arjan82]

This seems to be a duplicate

 

[FactChecker]

The pressure in place A has a vertical component (lift) and also a horizontal component (thrust) ... So how would the integral "know" in which direction the pressure acts?

Certainly, a person who is designing a wing knows how it is shaped and what the tilt of the surface is. A wing would usually not have a shape that has a simple, closed-form equation. Some sort of numerical method would be used to estimate the integral. Wind tunnels measure the forces directly.
On one of your other threads, @cjl made an interesting point that only the projection of a surface section on the horizontal axis is needed

 

[Jurgen M]

This seems to be a duplicate

Moderators please delete this topic, members at classic physics is far more active than here so I ask there. Plus aerospace is branch of classic physics.

 

[FactChecker]

Plus aerospace is branch of classic physics.

No. Aerospace is an application. It includes anything that is needed for that application -- specialized physics, math, structures, engine design, control law design, materials, navigation, etc. I would think that practically none of the aerodynamic subjects are adequately covered in classic physics.

 

[Jurgen M]

No. Aerospace is an application. It includes anything that is needed for that application -- specialized physics, math, structures, engine design, control law design, materials, navigation, etc. I would think that practically none of the aerodynamic subjects are adequately covered in classic physics.

Physics...classic physics...mechanics...fluid mechanics...fluid dynamics...aerodynamics(aerospace=astronautics+aeronautics)

tasks/question with calculation is not well accepted here, I have feeling here people don't want to calculate, rather talk in general..

I need people who love explain with real example "talk with math". Some members from Classic department are genius.

 

[russ_watters]

1. This is the correct forum for the question. People who haven't studied aerospace specifically won't necessarily be familiar with this issue.

2. Much of the reason you don't get many/good responses is that you don't ask good questions. You ask overly-broad questions and ask for a lot of information in response while not showing you've done much of your own research. It doesn't make people want to put in a lot of effort to help you. The concept you are asking about is demonstrated in standard aero labs in college. A quick google turns up tons of experimental procedure walk-throughs and reports. For example, here's the first link from a google of "wind tunnel lab lift from pressure array":
http://maecourses.ucsd.edu/callafon/labcourse/handouts/Wind_TunnelExpt_Writeup.pdf
Please read it (or others) and refine your questions if you have any remaining.

 

[FactChecker]

Physics...classic physics...mechanics...fluid mechanics...fluid dynamics...aerodynamics(aerospace=astronautics+aeronautics)

tasks/question with calculation is not well accepted here, I have feeling here people don't want to calculate, rather talk in general..

I need people who love explain with real example "talk with math". Some members from Classic department are genius.

A standard old reference on the subject is "Theory of Wing Sections"
There are some real experts on the subject (I am not one) that contribute to this section. IMHO, any person who tries to answer your question, giving an actual example and doing the calculations, is probably full of BS. And anyone who says that this is just a part of classical physics is full of BS.

PS. I worked at a major airframe manufacturer with the flight control design group for 35 years and know that the majority of people doing that work were from aeronautical engineering departments, not from physics departments.

 

[Jurgen M]

@russ_watters you can close this thread.

 

[russ_watters]

Closed on OP request.