Abstract: The different relative thickness of elliptic airfoils was simulated to study the laminar flow separation and the structure of flow field in the range of low Reynolds numbers by the method of computational fluid dynamics. The results showed that a leading-edge separation bubble forms on the thin elliptical airfoil at low Reynolds numbers， which accounts for high lift coefficient and lift-drag ratio at a small angle of attack. The laminar separation bubbles gradually disappear at the leading edge and appear at the trailing edge with the increase of relative thickness. The size of the leading-edge separation bubbles of the thin elliptic airfoil gradually reduces with the increase of Reynolds numbers. However， the phenomenon of transition and reattachment disappears at lower Reynolds numbers; at the same time， the size and position of the vortex at the trailing edges of the airfoil are also greatly affected by the appearance of laminar separation bubbles. The relative thickness and Reynolds number change the aerodynamic characteristics by influencing the size and position of laminar separation bubbles on the upper surface of the elliptic airfoil and the structure of separation vortex at the trailing edge.

Key words: elliptic airfoil; low Reynolds number; relative thickness; aerodynamic characteristics; laminar separation bubble