A wind profile represents a property of a load case to which the "Wind Simulation" analysis type is assigned (see the image Selecting "Analysis Type" of Load Case ). In the "Load Cases & Combinations" dialog box, select the "Wind Simulation" tab (1).
Click the
button in the "Wind Profile area" (2). The New Wind Profile dialog box appears.
The wind profiles are managed in the Load Wizards category of the navigator. You can also use the shortcut menu to define a new wind profile.
Wind Profile Type
In this area, select the Wind Profile Type from the list. It can be either "User-Defined" where you can manually define the properties or "According to Standard" where the code is applied that you have set in the "Base Data" of the model.
Properties
User-Defined Profile
When you have selected the user-defined type of profile, you can define the wind profile parameters manually. Enter the "Height" z and assign the "Wind Velocity" v in the "Properties" table.
By default, the "Turbulence Intensity" values are controlled by the value defined next to the "I" check box below the table. When the "Consider turbulence" is set on the Main tab of the "Wind Simulation Analysis Settings" dialog box, you can thus consider the turbulence intensity as a global percentage. It is the ratio of root-mean-square of the turbulent velocity fluctuations to the average velocity at the same location over a period of time. An idealized flow of air with absolutely no fluctuations in air speed or direction would have a turbulence intensity value of 0%. For high-turbulence cases, the turbulence intensity is typically between 5% and 20% (see CFD Online). The turbulence intensity is set to 1% by default to cover most medium- and low-turbulence cases.
Info
When you clear the "Set Uniform Turbulence Intensity" check box
below the table, you can define the turbulence intensities for each height level.
Profile According to Standard
The wind load is determined over the height of the building, depending on standard-specific parameters. The standards EN 1991‑1‑4 [1], ASCE/SEI 7‑16 [2], and NBC&cnbsp;2015 [3] are available for selection. The Wind Profile image above illustrates the parameters associated with EN 1991‑1‑4 [1]. When a different standard is set, the content of this section is adjusted to the regulations of the code.
When you activate the text box next to the "Terrain category" in the "Parameters" branch, different categories are available for selection. They depend on the standard and National Annex that you have set in the "Base Data" of the model.
For some National Annexes, the wind velocity is also dependent on the altitude of the terrain.
As the result of all parameters, the "Fundamental wind velocity" vb,0 is displayed. The wind profile is calculated from this value, taking into account the overall height of the model. According to EN 1991‑1‑4 [1], 4.2, this value is the characteristic 10 minutes mean wind velocity, irrespective of wind direction and time of year, at 10 m above ground level in open country terrain with low vegetation, such as grass and isolated obstacles with separations of at least 20 obstacle heights. You can review the wind velocities of every level in the table (below, left) and the left chart on the right. Instead of the fundamental wind velocity, you can "Consider the mean velocity". According to EN 1991‑1‑4 [1], 4.3, the mean wind velocity vm(z) at a height z above the terrain depends on the terrain roughness and orography. It is determined according to EN& 1991‑1‑4 [1], Expression& (4.3). This accounts for the fact that effects of peak velocity pressure appearing on the model are considered by a specific wind tunnel simulation, which allows for the application of lower mean velocities. When this option is activated, the table and chart are updated.
The profiles of the mean velocities vm are specified in the National Annex for Germany, Table& NA.B.2 for the four terrain categories, for example.
The "Density" of the air is dependent on the altitude, temperature, atmospheric pressure and humidity. It has an effect on the dynamic behavior of the fluid.
