Pitot-static probes in transonic flow

Carter Nelson

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Dec 17, 2003, 1:06:13 PM12/17/03

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Does anyone have any data or references for the performance of a simple
pitot-static probe in transonic flows with varying amounts of flow angle? By
simple pitot-static probe I am referring to probes of this design:

http://www.unitedsensorcorp.com/pitot.html

I am interested in how the probe measured total and static pressure vary
with both flow angle and Mach number, with flow angle varying over +/- 30
degrees and Mach ranging from 0.3 (or some incompressible low end) up to
1.3.

I have some subsonic (incompressible) information, but I am also curious how
the formation of shocks at the higher Machs will play into things.

Thanks,
Carter

Steve S

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Dec 18, 2003, 7:17:04 PM12/18/03

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First, probes of this design are not intended for the flow angle
variations you describe, regardless of flow regime. This type of
probe has a very narrow band of flow angle variation to be able to
resolve static and total pressures. Now, if you were able to null the
probe (i.e. rotate with flow angle to find maximum pressure at the
total pressure port), then you can resolve total and static quantities
as well as know the flow angle based on the angle of the probe.
Transonic adds additional considerations, such as a shock wave. If
one is present, you would need to correct your readings accordingly -
a calibration would be required to determine these corrections.

What are you ultimately trying to determine? We may be able to select
a different type of probe depending on your needs.

Carter Nelson

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Dec 19, 2003, 12:52:52 PM12/19/03

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I am trying to determine how bad is bad. Realizing that all of the things
you mention will occur, I want to know how these will effect the probe
readings:

PtProbe / PtInf = f(Mach, Flow Angle)
PsProbe / PsInf = g(Mach, Flow Angle)

What would these surfaces look like over the ranges I mentioned in my
previous post (Flow Angle = - 30 to +30 deg, Mach = 0.3 to 1.3) ?

I have no target application at this time. However, in the course of my job,
I have come across the need to answer this question a few times. In these
instances, the application has been the surveying of a flow field in which
the flow angle and Mach number varies over the ranges mentioned above.
Someone then asked, "Well, what if I just stick this pitot-static probe in
there and use that? How bad would that be?" My guess is, "pretty bad", but I
am curious if somewhere out there is quantifiable data to back this up.

Greg Esres

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Dec 19, 2003, 8:12:12 PM12/19/03

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<<Does anyone have any data or references for the performance of a
simple pitot-static probe in transonic flows with varying amounts of
flow angle?>>

Have you checked the NACA server? I read at least one article there
discussing Pitot tube accuracy, but don't recall if they went into the
transonic range.

Mary Shafer

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Dec 22, 2003, 12:36:25 PM12/22/03

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Try going to the Dryden Web site, at www.dfrc.nasa.gov and going to
the research paper archive. Ed Haering did a lot of good work on
pitot-static calibration and correction.

You can also look at Shafer's paper on upwash and sidewash corrections
for the F-8 DFBW. That has a bit about some interesting shock
impingement on the beta vane on the NACA noseboom.

You might also looks for SEADS research on the Orbiter. SEADS is a
flush air data system (FADS). Dryden also flew the X-15 ball nose,
but I don't know if that was in unlimited-access reports.

Mary

--
Mary Shafer Retired aerospace research engineer
mil...@qnet.com

Ed Ruf

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Dec 22, 2003, 12:37:13 PM12/22/03

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To help out the NACA archive sever may be found at
http://naca.larc.nasa.gov