CFX Turbo blade loading not matching to expected theory
 

Hi folks,

Has anyone seen results like this before?

I recently performed the example problem: workshop #3 “Centrifugal Pump with Volute” which I found at https://support.ansys.com/AnsysCusto...ANSYS+CFX+16.2

In Turbo the chart “Blade Loading” If I plot Streamwise vs. Pressure it looks as expected…. ( I used what is labeled as “Blade 6”)

Attachment 64919

But when I ask for it to plot Streamwise vs. Velocity I get the following:

Attachment 64920

Now the problem with the above chart is it seems to go against the theory given in Centrifugal pump books such as (two examples being Stepanoff and the other being Gulich).

The first picture above shows the pressure going up fairly evenly along the blade path. This is to be expected. However the second picture shows that velocity profile showing that the higher velocity switches from one side of the blade to the other. Higher velocity should be located on the suction side of the blade (according to theory). See “Centrifugal Pumps”, 3ed. By Gulich, page 86. So I am trying to gain an understanding of why this is happening on the velocity vs. Streamline graph.

Any help would be appreciated.