A novel method for extending the calibration range of five-hole probe for highly three-dimensional flows

Velocity, vorticity, and mach number

A Comparison of Data-Reduction Methods for a Seven-Hole Probe

It is common in the calibration of multihole probes to curve-fit the calibration data in order to determine a relationship between measured port pressures and flow properties. The parameters used in these techniques typically lack a theoretical background. In this article, a functional relationship is developed, based on theoretical considerations, that relates the port pressure directly to the flow properties and details a procedure that enables flow properties to be determined from the measured pressures of the multihole probe. The method is simple, easy to implement and provides a better understanding of the multihole probe operation in a three-dimensional flow.

Development of a functional relationship between port pressures and flow properties for the calibration and application of multihole probes to highly three-dimensional flows

Multihole pressure probes are frequently used to gather e ow data, sometimes in highly three-dimensional e ow. If the e ow is reversed, no method currently exists for determining whether the multihole probe is facing the right direction for data acquisition, and that the e ow is as such. A seven-hole probe is rotated in yaw by 360 deg, and rules are formulated to determine if a seven-hole probe is in a reversed e ow. The current study allows seven-hole probes to be used for gathering data in steady reversed e ows and gives an indication whether a pressure probe is insufe cient for the measurement instrument, as in the case of highly recirculating unsteady turbulent e ows. An application of the technique thus developed is also given.

Examining the Effect of Flow Reversal on Seven-Hole Probe Measurements

In this paper, a non-nulling calibration method using a seven-hole pressure probe in the range of at intervals both in yaw and in pitch planes is developed and reported. Calibration is carried out in two stages, low angles (for the maximum centre hole pressure) and high angles (other cases). On the basis of the maximum probe pressure reading, the calibration region is divided into seven zones; one central zone and six side zones. The calibration coefficients are derived for each zone. For interpolation, a localized two-variable polynomial is used at each point with the calibration data surrounding it. Zone extension is another useful feature developed here, in which each boundary point of every zone is extended to the nearest calibration point of the adjacent zone. By doing so, for a measuring point falling in between the boundaries of two adjacent zones, one employs the extended zone boundary data for fitting a polynomial. In addition to calibration data, additional data are acquired in the calibration tunnel. These data are used as measured data and calibration curves of suitable zones are used to derive flow parameters. In general, the interpolation errors in flow angles are found to be within and the errors in total and static pressures are within 0.5% and 1% of the dynamic pressure respectively.

A method of calibration of a seven-hole pressure probe for measuring highly three-dimensional flows

The present paper reports results of an experimental investigation on the effects of tip clearance in a high deflection annular turbine rotor cascade. The measurements are carried out at the inlet, in the blade passage and at the exit of the cascade using a five-hole probe and a seven-hole probe. The results indicate that the incoming flow to the rotor cascade is uniform and the incidence is about ′2°. When the clearance is increased, the size and the magnitude of the tip clearance loss region increase. The flow near the hub experiences overturning, whereas near the casing the flow substantially underturns due to tip clearance. The underturning increases with tip clearance. Secondary and tip clearance losses steeply increase downstream of the blade trailing edge indicating losses due to the wake and clearance flow mixing with the main flow.

C. Venkateswara Babu

Papers

A method of calibration of a seven-hole pressure probe for measuring highly three-dimensional flows

Experimental investigation of tip clearance effects on flow field in an annular turbine rotor cascade