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Experimental study of laminar separation phenomenon combining with numerical calculations

The accuracy of experimental results basically depends on the accuracy of wind tunnel and the quality of smoke on density and constitutive materials. Experimental results permit to determine the position of separation and the form of turbulent region followed from the separation point. Numerical studies were simultaneously realized. Based on obtained experimental and numerical results, the report presents also the comparison between the laminar separation and the turbulent separation. | Vietnam Journal of Mechanics, VAST, Vol. 33, No. 2 (2011), pp. 95 – 104 EXPERIMENTAL STUDY OF LAMINAR SEPARATION PHENOMENON COMBINING WITH NUMERICAL CALCULATIONS Nguyen Manh Hung, Hoang Thi Bich Ngoc Hanoi University of Technology Abstract. The separation is much more sensitive for laminar flow than for turbulent flow. These remarks have been attested for both subsonic and supersonic flows. However, they are not applicable to transonic flows when there are interactions between boundary layer and shock wave. Along with the Reynolds number, the Mach number is a necessary dimensionless parameter for the condition and the mechanism of separations. The report presents one part of studies on laminar separation with Mach number of incompressible flow. The laminar regimes correspond to flows through wind turbine blades. Our experimental work for laminar separation phenomenon was carried out in a subsonic open circuit wind tunnel by taking photographs. The accuracy of experimental results basically depends on the accuracy of wind tunnel and the quality of smoke on density and constitutive materials. Experimental results permit to determine the position of separation and the form of turbulent region followed from the separation point. Numerical studies were simultaneously realized. Based on obtained experimental and numerical results, the report presents also the comparison between the laminar separation and the turbulent separation. Keywords: Laminar separation, Experimental study, Numerical calculation. 1. INTRODUCTION For subsonic flows over a plane plate or a profile, Reynolds number Re= 105 can be considered as Reynolds number of transition [1]. With Re< 105 , flow is laminar. The Reynolds number characterizes the turbulence. The condition of separation still depends on pressure gradient concerning the geometry and the incidence. In the same conditions of geometry and incidence, the laminar flow has a separation, but the turbulent flow can have not one. The higher .