Experimental investigation of a vane probe blockage effect in a small wind tunnel

• Experimental investigation of the effects of vane probe positioning in a small test section. • Calibration results are most influenced by the probe’s insertion depth. • Comparative measurements revealed no systematic errors. • The blockage effect can be minimised by examining velocity perturbation fields. The blockage effect of a vane probe with a high blockage ratio is investigated in a small, open-circuit wind tunnel with a box-type test section. A laser Doppler anemometer is utilized to determine a reference air velocity. The study examines how different cross-sectional and axial positions of the vane probe in the test section affect the calibration results. The experiments were designed so that no access to the test section was required during individual test series, in which the probe was moved along a single direction within the test section. The results highlight the importance of the positioning of the vane probe, in particular the effect of insertion depth. The test results were also analysed in the context of literature-based uncertainty estimates related to blockage effects. Measurements of the velocity fields upstream of the vane probe showed that the points for the reference velocity measurement were in regions where the velocity disturbances caused by the vane probe were minimal. Comparative measurements conducted in a larger, closed-circuit wind tunnel revealed no systematic shifts directly attributable to the applied calibration procedure or blockage effects. With the aim of minimizing the blockage effects, the presented approach based on measurement of velocity perturbation fields allows a qualitative assessment of the adequacy of selected reference velocity measurement points.