This report describes the calibration of a non-nulling, conical, seven-hole pressure probe over a large range of flow onset angles. The calibration procedure is based on the use of differential pressures to determine the three components of velocity. The method allows determination of the flow angle and velocity magnitude to within an average error of 1.0° and 1.0% respectively. Greater accuracy can be achieved by using high quality pressure transducers. Also included is an examination of the factors which limit the use of the probe, a description of the measurement chain, an error analysis, and a typical experimental result. In addition, a new general analytical model of pressure probe behavior is described and the validity of the model is demonstrated by comparing it with experimentally measured calibration data for a three-hole yaw meter and a sevenhole probe.

Modelling, calibration, and error analysis of seven-hole pressure probes

Extensive parametric study of vortices shed from the tips of airfoil vortex generators has been conducted to determine the dependence of initial vortex circulation and peak vorticity on elements of airfoil geometry and impinging-flow conditions. The vortex generators were symmetric airfoils examined in subsonic airflow on the surface of a straight pipe. The circulation and peak-vorticity data were derived from cross-plane velocity measurements acquired with a seven-hole probe one chord length downstream of the airfoil-trailing-edge-tip location. Circulation and peak vorticity are observed to be proportional to the freestream Mach number, the angle of attack, and the span-to-boundary-layer-thickness ratio

Parametric Study of Vortices Shed from Airfoil Vortex Generators

We present the development of a data reduction algorithm for non-nulling, multihole pressure probes in compressible, subsonic flowfields. The algorithm is able to reduce data from any 5- or 7-hole probe and generate very accurate predictions of the velocity magnitude and direction, total and static pressures, Mach and Reynolds number and fluid properties like the density and viscosity. The algorithm utilizes a database of calibration data and a local least-squares interpolation technique. It has been tested on four novel miniature 7-hole probes that have been calibrated at NASA Langley Flow Modeling and Control Branch for the entire subsonic regime. Each of the probes had a conical lip with diameter of 1.65 mm

The Compressible Calibration of Miniature Multi-Hole Probes

A fault-tolerant neural network algorithm was successfully developed for use with flush air data sensing systems. This algorithm is composed of a combination of aerodynamic and neural network models used to translate a discrete pressure distribution from the nose of an aircraft into a set of air data parameters, including static pressure, dynamic pressure, Mach number, angle of attack, and angle of sideslip. Techniques were developed to detect and eliminate the effect of a lost signal from the measured pressure distribution. This system was evaluated with archived data, and its performance was compared with a signal processing system based completely on aerodynamic models

Fault-Tolerant Neural Network Algorithm for Flush Air Data Sensing

Described here is the calibration of a non-nulling, conical, seven-hole pressure probe over a large range of flow onset angles The calibration procedure is based on the use of differential pressures to determine the three components of velocity The method allows determination of the flow angle to within 05 deg and velocity magnitude to approximately 10 percent Also included is an examination of the factors which limit the use of the probe, a description of the measurement chain, an error analysis, and a typical experimental result In addition, a new general analytical model of pressure probe behavior is described and the validity of the model is demonstrated by comparing it with experimentally measured calibration data for a three-hole yaw meter and a seven-hole probe

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Calibration of seven-hole pressure probes for use in fluid flows with large angularity

A non-nulling seven-hole conical pressure probe capable of measuring flow conditions at angles up to 75 deg relative to its axis is described. The theoretical rationale of the seven-hole probe is developed and the calibration procedure outlined. Three-variable third-order polynomial functions are used to represent local values of relative flow angles, total pressure, and total minus static pressure. These flow properties are determined explicitly from measured probe pressures. Flow angles are determined within 2.5 deg and Mach number within 0.05 with 95% certainty. The probe can be used in subsonic compressible and incompressible flows.

Seven-hole cone probes for high angle flow measurement Theory and calibration

A seven-hole conical pressure probe capable of measuring flow conditions at angles up to 75 deg relative to its axis is described. The theoretical rationale of the seven-hole probe is developed and the calibration procedure outlined. Three-variable third order polynomials are used to represent local values of total pressure, static pressure, Mach number and relative flow angles. These flow conditions can be determined explicitly from measured probe pressures. Flow angles may be determined within 2.5 deg and Mach number within 0.05 with 95% certainty. The probe was calibrated in subsonic compressible and incompressible flows. Results of a calibration of four seven-hole probes are presented.

K. N. Everett

Papers

Seven-hole cone probes for high angle flow measurement Theory and calibration

Theory and calibration of non-nulling seven-hole cone probes for use in complex flow measurement