Learning Forum

[BainJT]

Hello, 

Using Ansys CFX I'm working on an array of tidal stream turbines, using the actuator disk theory to model them. It is a staggered array, with two turbines upfront with a third turbine behind in the wake of the front two. 

I have successfully drawn, meshed and applied the subdomains to the turbines. A momentum sink has been applied to the turbines as I have made them a subdomain. The momentum sink is a function of the fluid velocity before the turbine. For the front two turbines, the expression is easy enough to determine as the velocity required is equal to that of the inflow condition of the control volume. 

The third turbine, or rear turbine in the array, is where I am facing difficulty. The expression still remains the same for the momentum sink of the turbine, but due to the flow interacting with the front two turbines the velocity before this rear turbine needs to be determined. 

Is there a way in which I can select a particular point in the flow field and say the velocity at this point is the velocity to be inputted into the momentum sink expression? 

I'll be happy to elaborate further if required. 

Many thanks, 

James. 

[Rob]

You should be able to use the velocity at a point/face/volume in the expression. Check the location syntax for CFX Expressions. 

[BainJT]

Many thanks once again!