Upper Surface Of Airfoil Research Articles

Separation Control of NACA0015 Airfoil using Plasma Actuators

Separation control of NACA0015 airfoil using plasma actuators was investigated. Plasma actuators in spanwise array, which consists of 21 electrodes, were located at the leading edge of the airfoil to give temporal periodic disturbances with phase variations into its boundary layer. The cord length of the airfoil was c = 100mm and corresponding Reynolds number was fixed at Re = 63,000. Non-dimensional frequency of the disturbance was chosen at F+ = 0.5 or 6. The gap between adjacent electrode was set as 1mm, and phase difference of the temporal periodic disturbances between adjacent electrode was set at φ = 0 or π. Velocity field was measured by conventional two-component PIV using a CCD camera (Imperx, B1922, 1920 x 1460pixels) and Nd-YAG laser (Quantel, Evergreen, 140mJ/pulse). Both large field of view (FOV) images capturing whole wing with surrounding flow and smaller FOV images focused on the separation bubble near leading edge were evaluated. Surface pressure was monitored by pressure transducers through pressure taps on the upper surface of airfoil. Lift and drag against the airfoil were measured using a two-component force balance.

0207 ステップ後方流れに生じる剥離剪断層の再付着

In low Reynolds numbers region, a laminar separation and laminar separation bubble was observed on upper surface of airfoil. This flow field could be realized over a backward-facing step. The numerical calculation over a backward-facing step was carried out to examine both separation and reattachment of shear layer at Reynolds number of 2,000 based on the step height. The flow after the separation reattached of being instability of separated share layer by amplifying the disturbance. In reattachment region, the time change of reattachment position indicated that the dominant spectrum was the high and frequency components. The reattachment position was locally increased by this high frequency component. As a result, we confirmed that the reattachment position of span-wise direction was three-dimensional.

Numerical study of separation on the trailing edge of a symmetrical airfoil at a low Reynolds number

This study focuses on the trailing-edge separation of a symmetrical airfoil at a low Reynolds number. Finite volume method is adopted to solve the unsteady Reynolds-averaged Navier–Stokes (RANS) equation. Flow of the symmetrical airfoil SD8020 at a low Reynolds number has been simulated. Laminar separation bubble in the flow field of the airfoil is observed and process of unsteady bubble burst and vortex shedding from airfoil surfaces is investigated. The time-dependent lift coefficient is characteristic of periodic fluctuations and the lift curve varies nonlinearly with the attack of angle. Laminar separation occurs on both surfaces of airfoil at small angles of attack. With the increase of angle of attack, laminar separation occurs and then reattaches near the trailing edge on the upper surface of airfoil, which forms laminar separation bubble. When the attack of angle reaches certain value, the laminar separation bubble is unstable and produces two kinds of large scale vortex, i.e. primary vortex and secondary vortex. The periodic processes that include secondary vortex production, motion of secondary vortex and vortex shedding cause fluctuation of the lift coefficient. The periodic time varies with attack of angle. The secondary vortex is relatively stronger than the primary vortex, which means its influence is relatively stronger than the primary vortex.

Experimental Research on Transition and Flow Separation of Laminar Airfoil

Experimental research on transition and flow separation of laminar airfoil and the influence of transition and flow separation on the performance of laminar airfoil are carried through. The experimental device and instruments used in the research are introduced. It is shown from the experimental results that at certain scope of attack angle, flow transition shifts from 50%c to 30%c on the upper surface of airfoil model along with 1 degree increase of airfoil attack angle; For flow speed of 35m/s and 50m/s with attack angle from 4 degree to 8 degree, flow separation position don’t vary but only separation scope increase; For flow speed of 15m/s laminar flow separation on the upper surface of airfoil take place at attack angle of 4 degree, flow become attaching at attack angle of 6 degree and turbulent flow separation take place at attack angle of 8 degree.