Hello everybody on forum

I would like to know whether which side (i.e pressure or suction side ) of turbine /pump blade will have more boundary layer effects.

regards

sameer mohrir

Boundary layers effects are most important on the suction side - the decelleration in the downstream part of the suction side makes the boundary layers grow and can cause separation.

On the pressure side you can sometimes have separation close to the leading edge, but other than the boundary layer effects are often quite small compared to what happens on the suction side.

In the case of supersonic turbines you will also sometimes have shock-boundary layer interaction phenomena on the suction side.

Hello Jonas Larsson

Thanks for clarification

sameer

(1). I would say that in general it is true under design conditions, that suction side will subject to adverse pressure gradient and thus it will have thicker boundary layer. (2). But in real world operating conditions, the mass flow rate can change, the RPM can change, so the flow separation can occur on on either side of the blade. This is similar to an aircraft flying upside down, the pressure side suddenly becomes the suction side. (3). So, I would say that it depends on the actual operating condition, whether it is design condition or off-design condition.