Learning Forum

[Metin]

Hello,nI'm currently analyzing a wind turbine (only one blade is being analyzed). I have a flow domain and there is a blade which is extracted from the flow domain with the Boolean command. I selected the faces of the blade in the name selection. nWhat should I choose for the boundary conditions of this blade if I'm using MRF method(blade is a wall obviously)? Should I leave it as it is which is basically stationary wall/relative to cell zone? Or should I change it to moving wall/relative to cell zone and give 0 rpm rotation to it? nI read that when we are using MRF approach, it's as if we're standing on the blade and therefore blade is stationary for us and everything else is rotating. I would really appreciate if someone can clarify this boundary condition.nBest Regards,

[Rob]

You set the fluid as rotating (frame motion) and the blade moving at zero relative velocity. Make sure you get the axis right! You also need to read up on cyclic periodic boundary conditions. n

[Metin]

Here is a picture of my domain.nHere is my blade displayed by itself only. nBlade is supposed to rotate COUNTERCLOCKWISE.nHere are the settings for my flow domain. I tried using -72 and +72 rpm in my analysis and -72 rpm seems to give reasonable results. nHere is my question. When we use the right hand rule, our thumb should point in the Z direction and I gave it a value of 1 in the Z as you can see in the Rotation-Axis Direction section. According to this information, +72 rpm should be in the counterclockwise direction but it gives wrong results. I checked Ansys course on Edx and they also choose a negative rpm value even though the blade in that course is rotating clockwise. nCould you also clarify the logic behind this negative and positive rpm values?.