# [TurboGrid] Backward Facing Step at Hub

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 August 18, 2020, 22:10 Backward Facing Step at Hub #1 New Member   Join Date: May 2019 Posts: 7 Rep Power: 7 Hello everyone, For my thesis work I am meshing an axial turbine blade with ANSYS Turbogrid. The geometry provided, however, has a backward-facing step on the stator-rotor interface. My intention was therefore to divide the rotor inlet into two parts (which would be set as inflow and wall boundary conditions). Would anyone have any idea how it is possible to split blocks on a reference surface? Otherwise, a possible alternative would be to import the Turbogrid mesh into Pointwise. However, I cannot find a suitable way to do this conversion. Has anyone ever had to switch from Turbogrid to Pointwise? Thank you in advance! Andrea

 August 19, 2020, 10:05 #2 Member   Henrique Stel Join Date: Apr 2009 Location: Curitiba, Brazil Posts: 93 Rep Power: 17 Could you attach images to give a better idea about what you want to do?

 August 19, 2020, 10:29 #3 New Member   Join Date: May 2019 Posts: 7 Rep Power: 7 Thank you for your reply! To explain in a better way what I meant I attached a previous mesh created into Pointwise. In the picture inlet surface is splitted in two parts: the orange one is set as inflow boundary condition, while the yellow one (the backward facing step at hub) is set as wall boundary condition. Rotor_Step.jpg So what I am asking for is if it is possible to split the entire mesh at a certain radius (more or less as what Turbogrid do to create a shroud gap, but keeping the blade).

August 20, 2020, 07:29
#4
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Henrique Stel
Join Date: Apr 2009
Location: Curitiba, Brazil
Posts: 93
Rep Power: 17
Quote:
 Originally Posted by Turbofan Thank you for your reply! To explain in a better way what I meant I attached a previous mesh created into Pointwise. In the picture inlet surface is splitted in two parts: the orange one is set as inflow boundary condition, while the yellow one (the backward facing step at hub) is set as wall boundary condition. Attachment 79736 So what I am asking for is if it is possible to split the entire mesh at a certain radius (more or less as what Turbogrid do to create a shroud gap, but keeping the blade).
I'm still not 100% sure if I understood the problem, but from what I see you have a small step at the bottom of the inlet facing in the same direction of the inlet, right?

Well, if this is the case, so I don't think you will be able to split that on TurboGrid, either during the meshing process or by manually managing the hub/shroud (not sure to whom the step belongs to) curve points.

What you can do, however, is to displace the inlet back or forth so that the step will become a part of the hub itself, not the inlet (you can make it as a part of the rotor or the stator).

Another thing that you could try is to make the step as a part of the inlet as if there was no step at all, and then import the mesh on ICEM and try to manually assign the bottom faces as another part (the step). This one is tricky and "highly non-ideal" if we can call it that way but it's just something you could try, maybe it can serve you any purpose.

 Tags backward facing step, pointwise, turbine, turbogrid