K2 Engingeering _ Wind Load Application Inputs

florian_r · December 28, 2020, 4:33pm

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

AndersDeleuran · December 15, 2020, 3:23pm

Hi Florian, you can inspect the source code here:

github.com

CecilieBrandt/K2Engineering/blob/master/K2Engineering/K2Engineering/MeshWindLoad.cs

using System;
using System.Collections.Generic;
using Plankton;
using Grasshopper.Kernel;
using Rhino.Geometry;

namespace K2Engineering
{
    public class MeshWindLoad : GH_Component
    {
        /// <summary>
        /// Initializes a new instance of the MeshWindLoad class.
        /// </summary>
        public MeshWindLoad()
          : base("MeshWindLoad", "MWind",
              "Calculate wind load on a mesh",
              "K2Eng", "2 Load")
        {
        }

This file has been truncated. show original

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.

c.brandtolsen · December 16, 2020, 8:33pm

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

florian_r · December 19, 2020, 5:41pm

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

c.brandtolsen · December 20, 2020, 9:50am

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:

github.com

CecilieBrandt/K2Engineering/blob/master/K2Engineering/K2Engineering/Pressure.cs

using System;
using System.Collections.Generic;
using Grasshopper.Kernel;
using Rhino.Geometry;
using Plankton;
using KangarooSolver;

namespace K2Engineering
{
    public class Pressure : GH_Component
    {
        /// <summary>
        /// Initializes a new instance of the Pressure class.
        /// </summary>
        public Pressure()
          : base("Pressure", "Pressure",
              "A pressure load goal following the principle of the Ideal Gas Law and with forces perpendicular to the mesh faces",
              "K2Eng", "2 Load")
        {
        }

This file has been truncated. show original

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

//Cecilie

florian_r · December 22, 2020, 12:52am

Thanks Cecilie,

I will check that.

Florian
@c.brandtolsen