Abstract
This article deals with a new approach to the investigation of unsteady transonic flow fields around aerodynamic models and in blade cascades using a schlieren method of flow visualisation. The principle and the application of the Colour Streak Schlieren Method (CSSM) are defined. The characteristic flow field features were observed and analysed around an oscillating NACA 0012 airfoil under the conditions of transonic free stream Mach number (M∞ = 0.9), initial angle of attack (α = +4 deg), one amplitude of oscillation (Δα=±3 deg), and three frequencies of model oscillation (f = 1, 15, 30 Hz). There is a description of the terminal shock wave hysteresis across the investigated area, which was revealed in particular cases. Application possibilities of CSSM and its further development are discussed.
Highlights
Optical methods of flow visualisation are firmly connected with experimental research techniques in the field of high-speed aerodynamics
The aim of this paper is to describe a new method of flow field analysis which can reveal some hardly observable phenomena in unsteady transonic flows, and can obtain some quantitative data from schlieren video sequences
The Colour Streak Schlieren Method represents a new approach to flow field analysis based on optical records
Summary
This article deals with a new approach to the investigation of unsteady transonic flow fields around aerodynamic models and in blade cascades using a schlieren method of flow visualisation. The principle and the application of the Colour Streak Schlieren Method (CSSM) are defined. The characteristic flow field features were observed and analysed around an oscillating NACA 0012 airfoil under the conditions of transonic free stream Mach number (M¥ = 0.9), initial angle of attack (a = + 4 deg), one amplitude of oscillation (Da = ± 3 deg), and three frequencies of model oscillation (f = 1, 15, 30 Hz). Application possibilities of CSSM and its further development are discussed. Chord distance between streaks frequency of oscillation free stream Mach number streak thickness angle of attack amplitude of oscillation streak deflection density video sequence
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