196 Fermentation and Biochemical Engineering Handbook Figure 10b. Typical profile of airfoil at an angle of attack that gives fluids separation from the airfoil surface A310 22% 09A312 35% 88 315 7% Figure 11. Solidity ratio defined as a ratio of blade area to circle area. The solidity ratio for four different fluidfoil impellers is shown196 Fermentation and Biochemical Engineering Handbook Figure lOb. Typical profile of airfoil at an angle of attack that gives fluids separation from the airfoil surface. Figure 11. Solidity ratio defmed as a ratio of blade area to circle area. The solidity ratio for four different fluidfoil impellers is shown