1 Abstract Experimental investigation of flow field above a laminar airfoil in a transonic wind tunnel was conducted. The aim of the research was to provide a quantitative information about the shock position for various angles of incidence at Mach number = 0.7. The flow field in a test section of high speed blow down wind tunnel was investigated by means of Particle Image Velocimetry (PIV). The resulting instantaneous vector velocity field was processed in order to determine the variation of shock position above the airfoil. As expected, the shock moved closer to the leading edge while the angle of incidence was increased. More interestingly, the experimental data revealed an increase in shock oscillation amplitude for angle of incidence between 3° and 5°. Experiments allowed to quantitatively describe the transonic flow field above the airfoil by non-intrusive method. 1 General Introduction One of the most investigated fields of aviation research [19] is optimization of the aerodynamic performance of new aircrafts at low [2][8][21] and transonic speeds. Especially for airline transport the balance between the time of traveling and economy of flight require cruising speeds in proximity of critical Mach number of used airfoils. In such conditions the flow is often affected by the presences of nonlinearities and instabilities. The flow field oscillations are caused by interaction of the shock with the boundary layer. This interaction influences the development of the shock-induced separation bubble or rear separation [7]. The unsteady flow field with shock wave oscillations might cause unsteady buffet loads acting on airplane structure. Therefore, applied research on the transonic flow are important for control, economics and safety reasons. The experimental investigations of unsteady transonic flow over an airfoils was carried out since 1950s. Complex phenomena such as creation of shock, oscillations, buffet onset and shock wave boundary layer interaction was examined with pressure [9] and stress measurements [20], the flow filed was visualized Schlieren method [10]. A comprehensive review of recent progress in shock wave/boundary layer interactions research can be found in [6]. The Particle Images Velocimetry (PIV) is instantaneous whole field velocity measurements technique [12] applied in fluid dynamic research, aerodynamics [15][16] and related fields [18]. The PIV method was used for instantaneous whole field velocity measurements of flow at transonic speeds [5][11][13]. The SWBLI was investigated with PIV method by Giepman [3]. Hartmann [4] performed time resolved stereo PIV measurements of unsteady shock-boundary layer interaction on a supercritical airfoil. This paper presents application of PIV method for investigations of shock oscillations above the surface of an airfoil. The experiments was performed in high speed wind tunnel N-3 in Institute of Aviation, Warsaw, Poland. In a course of presented study a 2D vector velocity field of the flow over an airfoil for Mach number of 0.7 has been determined. The PIV measurements results were used for determination of the shock wave position in relation to the chord of the airfoil. The various angles on incidence for fixed freestream Mach INVESTIGATION OF UNSTEADY TRANSONIC FLOW FIELD ABOVE LAMINAR AIRFOIL BY PIV METHOD Wit Stryczniewicz*, Robert Placek*, Paweł Ruchała* *Institute of Aviation, Krakowska 110/114, 02-256 Warsaw, Poland Keywords: airfoil flow, transonic flow, shock oscillations, PIV