RWIND 3 is an outstanding tool for creating wind-induced loads on general structures. RWIND 3 is a separate program that is used externally to determine load cases and wind loads for RFEM 6 and RSTAB 9 models. For RFEM, the model may consist of beams, surfaces and/or solids in any composition. For RSTAB models, loads can be created for models that fully conform to the structural system, such as lattice towers or braced girders without cladding. RWIND uses a numerical CFD (Computational Fluid Dynamics) model to apply a fluid-mechanics simulation of the flow around objects in a wind tunnel. As a result of the simulation process, specific wind loads are created for RFEM or RSTAB.
A 3D mesh of finite volumes is used for the simulation. RWIND performs automatic meshing, while the overall mesh density, as well as the local mesh refinement near the model, can easily be set using just a few parameters. For the calculation of the air flow and the surface pressure on the model, a finite volume numerical solver for incompressible turbulent flow is applied. The results are then extrapolated on the model. RWIND has been designed to work with various numerical solvers. Currently, we recommend using the OpenFOAM® software package, which, according to our tests, gives very good results and is a widely used tool for CFD simulations. Alternative numerical solvers are under development.
RWIND 3 is able to read the topology from RFEM 6 and RSTAB 9 models as well as from *.stl, *.ifc, *.obj, and *.vtp files (importing *.stp and *.igs files is in preparation). Minor corrections of the model that may be required for corners or joints are applied automatically. The data relevant to the loading can be defined either in RWIND 3 or in the RFEM 6 / RSTAB 9 load cases. The latter option is recommended: It enables you to create load cases for the relevant wind directions and apply wind profiles according to specific standards. The effects of turbulence can be included optionally. The dimensions of the wind tunnel are set to the size of the model but can be modified, if necessary.
The results of the simulation include the pressure and velocity fields around the model, the streamlines, the surface pressure and the member forces. They represent the results of a stationary analysis. All results are illustrated by means of color maps (isobands) or isolines on the model, or by slicer planes within the wind tunnel. The streamlines can be displayed in an animated view, which makes it easy to evaluate the effects of laminar and turbulent flow. As an essential result of the simulation, loads are created for the RFEM/RSTAB model. They are exported to the respective load cases, where they are applied as FE nodal loads or member loads.
The common procedure for creating wind loads with RWIND 3 is as follows:
- Define the model data in RFEM 6 or RSTAB 9. Make sure that the 'Wind Simulation' add-on is activated in the "Base Data" dialog box.
- Open the "Load Cases & Combinations" dialog box. Define the load cases for the relevant wind directions and allocate the "Wind simulation" analysis type each.
- Define the "Wind simulation analysis settings" and the "Wind profile" for those load cases.
- Use the "Calculate Wind Simulation" function to export the model data relating to one of the load cases to the RWIND 3 program.
- In RWIND, you can review the settings of the wind tunnel, mesh, simplification of the model, and so on. Adjust the parameters, if necessary.
- Start the calculation in RWIND.
- Check the results.
- Quit RWIND and return to RFEM/RSTAB.
- Combine the wind load case(s) with other load cases in load and result combinations, if applicable.
- Finally, start the calculation of the deformations and internal forces.
Apart from the interactive application with RFEM 6 or RSTAB 9, RWIND 3 can be used as a stand-alone program for universal CFD analyses. Simply import the model you have created in your CAD application and perform the analysis in RWIND. The flow fields, surface pressures, drag forces, and so on, can be utilized for various fields of application, such as an analysis of closely spaced buildings or a pedestrian wind comfort simulation in a city.
We hope you will have a pleasant and successful time working with RWIND 3.