Jovan Isaković

The flow parameters control in wind tunnels is an area of intense research in recent years, with the aim of improving quality and efficiency of the wind tunnel operation. In this paper, an attempt is made to contribute to a better understanding of the stagnation pressure control in supersonic blowdown-type facilities. The stagnation pressure control strategy in the VTI Belgrade T-38 wind tunnel is discussed. An improved mathematical model for a supersonic wind tunnel is suggested and applied to the T-38 facility. Comparisons of simulation and experimental data are made to demonstrate accurate prediction of the facility response in supersonic flow conditions by the mathematical model. The model is used to incorporate a modified feedforward control in the original T-38 wind tunnel control system. The actual wind tunnel tests confirm model-predicted decrease of flow stabilization time and increase of available measurement time, bringing significant improvement in the wind tunnel operation efficiency.

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A necessity to test a standard model testing for establishing confidence in the wind-tunnel flow quality and the validity of the test-data has been recognized in the Experimental Aerodynamics Laboratory of the Military Technical Institute (VTI) in Belgrade. A new-implemented procedure for data quality assurance has been applied to the standard AGARD-B model testing in the VTI's large-subsonic wind-tunnel. Test-data obtained at Mach number 0.4 have been analized and correlated with those of the physically same model performed in the Canadian NAE (today operates as IAR) 5ft trisonic wind-tunnel and the T-38 trisonic wind-tunnel of VTI. Within-facility comparisons and inter-facility correlations of the standard test-data were done to certify an overall reliabilty of the subsonic facility as an initial step in the establishing the confidence prior to a forthcoming customer test.