# Simulation of an Actuator Disk - Question about Fan Boundary Condition

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 March 17, 2021, 13:58 Simulation of an Actuator Disk - Question about Fan Boundary Condition #1 New Member   Yael Join Date: Apr 2020 Posts: 3 Rep Power: 4 Dear all, As part of my school project I need to simulate a rotor disk to simplify the flow of a propeller. I'm working based on the results of an investigation ("CFD actuator disk solutions for a helicopter rotor in hover flight": http://www.tfd.chalmers.se/~hani/kur...tudyReport.pdf) Since no more details of how the simulation proceeds are given, my thesis supervisor told me I either have to use the Intake/Exhaust Fan conditions for a disc with a very small thickness, as shown in the image below: Rotor Disk.png However, I'm not sure if this is the correct approach. Reading "ANSYS FLUENT 12.0 User's Guide" I understand that I should use the Fan Boundary Condition for a disc with zero thickness, because that's where I can specify my Radial and Tangential Velocity, and from that, I can obtain the Pressure Jump Profile, but I'm also not sure of how to obtain this profile. When I specify the Velocity Profiles using UDFs I don't see any mass flow nor residuals of velocity. If anyone could give me a little guidance regarding the simulation of rotor disks would be very much appreciated! PS: The process, as described in the research, is as follows: "To solve this problem with the Fluent commercial code, it is necessary to specify in the CFD code the azimuthal and radial velocities, and the jump of pressure but the pressure jump equation is not known. For this, the first CFD case is created with a real disk to obtain the total pressure. It is assumed that there is no interaction between the flow above the disk and the flow below the disk if the total pressure is solved infinitely close to the disk. In order to apply the velocity profiles, a program in C language (called User Defined Functions) is created." Thank you once again for your attention!

 October 8, 2021, 13:33 #2 Member   Adithya Join Date: May 2021 Posts: 73 Rep Power: 3 Hi I am simulating a propeller powered aircraft and am also struggling with implementing the fan boundary condition. I don't have a solution for you, but rather more questions. I am using ANSYS Design modeleer and ANSYS meshing and Fluent. Did you create a surface and define it as a disc? Is this surface a second part in your tree, i.e, you do not boolean subtract it from the fluid domain like you would for walls? Are there any methods to be used while meshing the disc?

 April 20, 2022, 16:07 #3 New Member   Join Date: Feb 2022 Posts: 2 Rep Power: 0 Hi! Did you manage to find a solution? I am also working on a pretty similar model where I model the propeller as an actuator disk and used fan boundary condition. I have specified the pressure jump as constant and I have found an analogy for the tangential velocity (still trying to figure out radial) but my results are still not validated by the wind tunnel data. So, maybe we can help each other! Thanks!

 June 15, 2022, 16:25 #4 New Member   Sab Join Date: Jun 2022 Posts: 1 Rep Power: 0 Hi! I am working on a similar case right now and struggle to find the tangential velocity profile (polynomial coefficients). How did you set your tan velocity?

 Tags fan boundary condition, fluent, radial velocity, rotor, tangential velocity

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