Seven-Hole Pressure Probe

David Sumner, Ph.D., P.Eng., Professor

Department of Mechanical Engineering, University of Saskatchewan

 
 

Overview

The seven-hole pressure probe is a non-nulling, directional velocity probe used to measure the local time-mean velocity vector in wind-tunnel flows.  The origin of the seven-hole pressure probe was at the U.S. Air Force Academy.  The objective was to obtain meaningful velocity information at flow angles where a five-hole probe becomes ineffective.  The probe is sensitive to flow angles up to 80° from the probe axis.  Calibration of a seven-hole probe requires subjecting the probe to flows of known direction.  Two calibration data-reduction methods are commonly employed; namely, the (i) polynomial curve-fit method of Gallington and the (ii) direct-interpolation method of Zilliac.  In Gallington’s method, the calibration data are used to develop a set of response equations using a least-squares fit of directional pressure coefficients to third-order polynomials. In Zilliac’s method, the calibration data are interpolated directly without the need to determine response equations.

 

The probe is conical-shaped, with a cone angle between 30° and 45°, and has six outer pressure ports (1 through 6) surrounding a central port (7).  Pressure information from the seven holes is combined to compute four pressure coefficients, representing the local pitch angle, yaw angle, total pressure, and dynamic pressure. This information then yields the local velocity vector.

 

Seven-hole pressure probe (manufactured at the University of Waterloo in 1992).

Seven-hole pressure probe (manufactured at the University of Saskatchewan in 1999).

Measuring the tip vortex behind a NACA 2412 wing section in the low-speed wind tunnel.

Seven-hole probe nomenclature and reference angles.

 

 
Our Seven-Hole Probe

Our 3.45-mm diameter seven-hole probe was manufactured at the University of Saskatchewan by Engineering Shops.  The probe is machined with a cone angle of 30°.  The probe is comprised of seven, close-packed 1-mm diameter stainless steel tubes, fitted into an outer stainless steel sleeve.  An automated variable-angle calibrator was designed to mount the probe in the wind tunnel test section.  Two stepping motors are used to position the probe in pitch and yaw.  The in-situ calibration eliminates uncertainty caused by differences between the test flow conditions and the calibration flow conditions, such as unsteadiness and turbulence levels, often encountered when using a calibrator jet (such as for a hot-wire anemometer).  We use both of the prevailing calibration data-reduction methods.

 
 
Selected Seven-Hole Probe References

Cogotti, A., 1986, Car-wake imaging using a seven-hole probe, Aerodynamics: Recent Developments, SAE Publication SP-656, pp. 1-25.

Everett, K.N., Gerner, A.A., Durston, D.A., 1983, Seven-hole cone probes for high angle flow measurement: theory and calibration, AIAA Journal, 21, 992-998.

Gallington, R.W., 1980, Measurement of very large flow angles with non-nulling seven-hole probe, Aeronautics Digest, USAFA-TR-80-17, 60-88.

Gallington, R.W., Hollenbaugh, C.F., 1979, A fast method for accurate manufacture of small five-hole probes, Aeronautics Digest, USAFA-TR-79-7, 114-119.

Gallington, R., Sisson, G., 1980, Flow visualization using a computerized data acquisition system, Flow Visualization II, Proceedings of the Second International Symposium on Flow Visualization, Bochum, West Germany, pp. 777-784.

Gerner, A.A., Maurer, C.L., 1982, Calibration of seven-hole probes suitable for high angles in subsonic compressible flows, AIAA Paper No. 82-0410.

Gerner, A.A., Maurer, C.L., Gallington, R.W., 1984, Non-nulling seven-hole probes for high-angle flow measurement, Experiments in Fluids, 2, 95-103.

Payne, F.M., Ng, T.T., Nelson, R.C., 1989, Seven-hole probe measurement of leading edge vortex flows, Experiments in Fluids, 7, 1-8.

Pettersson, B., 1987, Calibration of seven-hole probes within Mach number range 0.50 - 1.30 in FFA high speed wind tunnel facility, Proceedings of the International Congress on Instrumentation in Aerospace Simulation Facilities, Williamsburg, VA, USA, pp. 156-164.

Rediniotis, O.K., Hoang, N.T., Telionis, D.P., 1993, The seven-hole probe: its calibration and use, Proceedings of the Forum on Instructional Fluid Dynamics Experiments, ASME FED Vol. 152, pp. 21-26.

Rediniotis, O.K., Pathak, M.M., 1999, Simple technique for frequency-response enhancement of miniature pressure probes, AIAA Journal, 37, 897-899.

Schlapkohl, S.R., Buzzell, W.A., 1982, Determination of the frequency response characteristics of a redesigned seven-hole pressure probe, Aeronautics Digest, USAFA-TR-82-3, 78-103.

Sumner, D., 2002, A comparison of data-reduction methods for a seven-hole pressure probe, ASME Journal of Fluids Engineering, 124, 523-527.

Sumner, D., Heseltine, J.L., Dansereau, O.J.P., 2004, Wake structure of a finite circular cylinder of small aspect ratio, Experiments in Fluids, 37, 720-730.

Zilliac, G.G., 1993, Modelling, calibration, and error analysis of seven-hole pressure probes, Experiments in Fluids, 14, 104-120.

Zilliac, G.G., 1989, Calibration of seven-hole pressure probes for use in fluid flows with large angularity, NASA Technical Memorandum 102200.

 

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Last updated: November 6, 2012