Abstract: Rotational velocity changes, via shear stress modification, due to air bubbles injection in a rotary device experimentally investigated. Air bubbles injected to the water flow crosses the neighbor of the hub which can rotate just by water flow shear stresses. Increasing air void fraction lead to decrease of shear stresses exerted on the hub surface until in high void fractions, the hub motion stopped as observed. Amount of skin friction decrease has been estimated by counting central hub rotations. Wall shear stress decreased as bubbles were injected in the all range of Re changing from 60378 to 61238 and also by increasing air void fraction from 1.22 to 3.06%. Skin friction reduction more than 80% achieved in this study as maximum measured volume of air fraction injected to fluid flow. Remarkable obtained skin friction reduction in this special case indicates the possibility of drag reduction by injection of low amount of air on rotary parts in liquid phase (e.g., water) while this effect is unfavorable in cases where shear stress is a useful phenomena (e.g., mixing).