K2 Engingeering _ Wind Load Application Inputs

Grasshopper Kangaroo
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Hi Cecilie,

I am using K2 & K2 Eng to analyze a mesh where i need to apply some wind load on it.
To be sure I apply it correctly, I would like to understand what is needed to input in the nA input of the component.

I seems to be a vector normal direction, but the unit is described as m2, which i am a bit confused.

Thanks for your help !

flo

@c.brandtolsen @AndersDeleuran

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Hi Florian, you can inspect the source code here:

I’m afraid I can’t offer more information than what is provided there (i.e. "VertexNormals", "nA", "The vertex normals scaled according to the associated voronoi area [m2]"). Which is probably the same information you already have.

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Hi @florian_r

The nA input to the “MeshWindLoad” component is a normal vector at a mesh vertex but instead of a unit vector it has to be scaled according to its tributary area (hence why the unit is m2).This is simply to reduce the number of inputs. I could also have asked for the vertex area in m2 and a vertex normal as two separate inputs.

The point is that the magnitude of the wind load acting at a vertex is related to the tributary area and the wind pressure. And sometimes it is useful to work with projected areas in relation to the wind direction. You can get that by specifying a plane in the “MeshVertexArea” component. This component outputs the “nA” for you so you don’t need to do that yourself.

Take a look at the “Cablenet” example file to see an example of how to use these components together:

I hope that answers your question.

Best,
Cecilie

1 Like
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Hi @c.brandtolsen @AndersDeleuran

Thanks for the reply !

So as i can understand, the wind force vector direction can be applied to the normal of mesh face/vertex.
I also understand that this vector direction is calculated for a certain geometry, considered as fixed, for example after a first form-finding step done by Kangaroo.

Is there a way to update the vector direction after each iteration of kangaroo ?
In my case, i am trying to apply wind force on a fabric which is free to move and therefore does not have equilibrium state.

I am trying to compare if the wind force from K2 Enginnering and the Wind goal from K2 itself gives any different results.

Thanks,

Florian

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Hi @florian_r

I think you should consider whether K2E is the right tool for your project? What are you trying to achieve? If you’re looking for a simulation of a fabric moving in the wind that behaves approximately right then just use K2 without K2E. If you’re trying to e.g. extract reaction forces or check the forces in the fabric in it’s equilibrium state then use K2E.

I do have an example of a force goal that updates iteratively during the simulation. Refer to the Pressure goal here:

But the point is that the structure reaches an equilibrium state even with this iterative load.

//Cecilie

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Thanks Cecilie,

I will check that.

Florian
@c.brandtolsen