Flow separation in a two-dimensional space occurs at a point and is determined by a change in the sign of wall shear stress. Post-separation flow may re-attach, forming a laminar separation bubble at a relatively lower Reynolds number, or it may not re-attach depending on Reynolds number, flow geometry, etc. When we transform the flow separation phenomenon to a three-dimensional plane, then the point of separation is not a point but a line over the surface of the body. In three-dimensional space, the flow has an additional direction to manoeuvre when it encounters an adverse pressure gradient. In our present work, we have carried out experimental investigation over the surface of a symmetrical, cam-bered NACA wing (streamlined body) and sphere (bluff body) in the low-speed wind tunnel to determine the separation lines. Our experiments were in the range of Reynolds number between 0.7 − 1.4 × 105, and we did oil flow visuali-sation to study the flow patterns. We have observed laminar separation bubble and quantified flow separation lines. Pressure measurement over surface of the body was used to corroborate the results observed from oil flow observations.


Flow leaves tell-tale signs as it moves over a solid body. Depending on the geometry of the body, pressure distribution over the body differs, and flow adjusts to local pressure distribution. In our present work, we have attempted to identify such flow patterns and their relation to Reynolds number and flow geometry.