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  • Answer

    The program RWIND Simulation is protected against unauthorized use. For a test of all program functionalities before the purchase, the program can be authorized with a limited trial license. To do this, proceed as follows:

    1. Run RWIND Simulation "As Administrator". To do this, right-click the RWIND Simulation symbol and select " Run as Administrator".

      Figure 01 - program start

    2. Confirm the authorization check with the 'Activate Now' function.

      Figure 02 - Authorization check

      This opens the " RWIND Simulation 1.xx Demo Authorization Status " dialog box.

    3. In the " RWIND Simulation 1.xx Demo Authorization Status " dialog box, click the " Activate Trial License" function in the lower part.

      Figure 03 - Activation of the trial license

      This opens the "Trial License" dialog box.

    4. The "Test License" dialog box mentions 3 steps. Follow these steps from 1 to 3.

      Open the website in step 1 with the "Request Activation Code" function and confirm the form filled with your contact information with "Submit Request".

      Figure 04 - Request for activation code

      Subsequently, you will receive an e-mail with an activation code to the specified e-mail address. Enter this activation code in the empty text box in step 2 and activate the limited-time test mode in step 3 with the "Activate trial license" function.

      Figure 05 - Activation of the trial license
    After successful authorization, you receive a confirmation message and can test the program for the specified test period without restrictions. After the trial period has expired, the program automatically switches to limited demo mode.

  • Answer

    The program RWIND Simulation is protected against unauthorized use. The program can be authorized with a single-user or network hardware key. For this, the single-user hardware key must be inserted at the local or the network hardware key at a computer available in the network. To do this, proceed as follows:

    1. Execute RWIND Simulation 'As Administrator'. It is necessary to right-click the RWIND Simulation symbol and select 'Run As Administrator'.

      Figure 01 - program start

    2. Confirm the authorization check with the 'Activate Now' function.

      Figure 02 - Authorization check

      This opens the "RWIND Simulation 1.xx Demo Authorization Status" dialog box.

    3. In the "RWIND Simulation 1.xx Demo Authorization Status" dialog box, select the "Hardware Key" option in the Authorization Method area.

      Figure 03 - Authorization method

    4. To authorize the RWIND Simulation program with a hardware key, an installed hardware key device driver is required on the computer where you want to run RWIND Simulation. Since many other programs use a similar software protection technology (RSTAB, RFEM, etc.), this device driver is already installed on the computer in many cases. Correct operation of the driver package can be found on the local website http://localhost: 1947/_int_/diag.html .

      If a working driver is displayed on this website, no action is necessary and you can proceed to the next point.

      Figure 04 - Device driver check

      If not, the necessary driver has to be installed with the "Install/reinstall device driver" function.

      Figure 05 - Device driver installation

    5. Make sure that the single-user hardware key is inserted at the local computer or the network hardware key at the network computer.

    6. After the hardware key has been completely initialized, authorize the program RWIND Simulation with "Check hardware keys and apply changes" and close the dialog box with "OK."

      Figure 06 - Authorization
    This process can be performed at any time on another computer with an installed version of RWIND Simulation. For a successful authorization, it is only necessary to ensure that either the single-user hardware key is inserted on the respective computer or the network hardware key inserted at the network computer has free licenses available.

  • Answer

    In RWIND Simulation, a video file can be created. Arrange the graphic on the screen and select Tools → Create Video File in the menu.

    In the "Create Video File" dialog box (Figure 1), you can define the name of the video file in a separate dialog box by using the [Search] button. It is possible to select different video file types. Furthermore, the quality and the recording frequency can be adjusted.

    Click the [Start] button to start the recording and the [Stop] button to stop the recording.
  • Answer

    Possible window, door and facade openings can be closed in RWIND Simulation using the model simplification (shrink-wrapping-mesh) for the wind flow calculation. This meshing option "seals" the imported models against wind flow entering the model with a concomitant internal compression load. To determine which opening should be closed and which openings should remain open, the program uses a size specification. Thus, all openings whose dimensions are smaller than the specified control dimension can be closed generically for the wind flow calculation in the numerical wind tunnel.

    Figure 01 - Velocity distribution for a closed and open structure

    In RWIND Simulation, the opening size specification is organized in the "Edit Model" menu of the respective models.

    Figure 02 - Specification of openings in RWIND Simulation

    The interface menu in RFEM or RSTAB organizes the opening size specification for the automated calculation of wind loads in the background in the "Simulate and Generate Wind Loads" menu under the "Wind Load" tab.

    Figure 02 - Specification of openings in RWIND Simulation

    Alternatively, additional surfaces in the opening areas can be considered for the simulation of a closed structure by means of an STL import.

  • Answer

    For the calculation, the program creates a solid mesh between the model and the outer sides of the wind tunnel. In this case, the solid mesh does not connect directly to the model geometry, but to a separate model enveloping mesh placed around the model geometry. This model enveloping mesh has a certain distance to the exact model geometry, depending on the model mesh setting (Simplified Model - Shrink-Wrapping-Mesh). Similar to the surrounding model enveloping mesh, the exact model geometry itself is also represented from an enveloping mesh, but on the exact model shape.

    Figure 01 - Mesh types

    With the OpenFOAM calculation, a print result is obtained on each solid element. These values are extrapolated to the respective edge nodes at the transition to the model. To determine the final surface pressures on the model geometry, the pressures at the edge nodes of the solid mesh are transformed to the exact model mesh envelope in a further step. In the event that the triangular meshing of the exact model mesh geometry is too rough, the last transformation process initiates a partial refinement of the exact model mesh envelope.

    Figure 02 - Difference between sheath mesh geometry and exact model geometry

  • Answer

    There is no load distribution displayed between the external facade elements at the example shown in Figure 01. Unloaded cells are not displayed according to the color scale during load distribution, but remain empty. Thus, the value on these elements is 0. This has the advantage that it is recognized immediately that the FE elements are not stressed.

    The cause of the problem can be visualized directly in RWIND Simulation. By default, calculations are based on a simplified model. Depending on the setting, it is possible to refine or coarsen the shell of the model. An FE mesh is placed over the structure, so to speak, and depending on the level of detail, this FE mesh snuggles against the model. Figure 02 shows the extent of the degree of detail that is too small. The surfaces standing on the façade are not displayed well enough and no wind flows between the cantilevered surfaces in the simulation, which is why these internal surfaces do not experience any wind pressure.

    The degree of detail can be adjusted in RWIND Simulation by "Edit Model" or directly in RFEM in the settings for the wind load simulation (see Figure 03). Optionally, the simplified model can also be completely deactivated in RWIND Simulation.

    In the case of a greater degree of detail (corresponds to a finer FE mesh), the cantilevered surfaces are displayed cleanly and the FE elements are stressed accordingly (see Figure 04 and Figure 05).

  • Answer

    The program RWIND Simulation is a program for numerical flow simulation . It is a tool for describing a wind flow problem around an object consisting of a system of partial differential equations with the output of an approximate solution on the basis of the finite-volume method. Similar to a simplified model, such a mathematical model provides information about the wind velocity field and the acting pressures on the surfaces of the wind-encircled object in a real wind tunnel.

    The standards describing wind effects on buildings and structural components (e.g. EN 1991-1-4, ASCE/SEI 7, etc.) are based on different principles. The rules and measures specify corresponding instructions for determining the wind loads for specific situations and applications. These formulas are undoubtedly correct for the assigned situations and the resulting values have been confirmed in practice.

    However, these guidelines do not describe all situations that occur in the real world of engineers. Here, infinitely different model shapes in the wind flow are processed, whereby each shape has its own high-grade influence on the resulting surface pressures caused by the wind load. However, for all model shapes not mentioned in the respective directives, the equivalent load from wind effects remains unclear.

    RWIND Simulation can help here in its role as an auxiliary tool for determining the resulting forces from the wind action. However, despite the use of RWIND Simulation, all requirements of the valid standardization must be ensured. The technology used in the simulation program may also provide further useful insights for sufficiently controlled object shapes.

    Figure 01 - Wind Flow Around Complex Antenna System
    Figure 02 - Surface Pressures on Complex Antenna Installation due to Wind Load

  • Answer

    The program RWIND Simulation provides an optional consideration of the k-ε and k-ω turbulence models for the numerical flow simulation. The necessary turbulence parameters can be manually specified or automatically determined from a user-defined turbulence intensity value. In the standard setting, the turbulence intensity is set to 1%. This value is based on a recommendation from the company CFD Support, which has many years of experience in the field of numerical flow simulation.

    Figure 01 - Effect of Turbulence Intensity

    In RWIND Simulation, the turbulence model is organized in the 'Parameters of Simulation' menu under the 'Turbulence' tab.

    The interface menu in RFEM or RSTAB organizes the turbulence model for the automated calculation of wind loads in the background in the menu 'Simulate and Generate Wind Loads' under the 'Settings' tab.

  • Answer

    The density and quality of the finite-volume mesh have a significant impact on the accuracy of the results. The denser the mesh, the more accurate the results. However, the computing time and the requirements of the computer's RAM increase with a denser mesh at the same time.

    The mesh of RWIND-Simulation can be divided into 3 categories:

    CategoryMesh densityMesh cellsCalculation timeHigh-performance computer
    Alow≤ 1 million
    several minutes
    ≤ 4 GB RAM
    Bmiddle-sized1 - 10 million
    several hours
    ≤ 16 GB RAM
    Chigh10 - 50 million
    several 10 hours
    ≤ 64 GB RAM

    In RWIND Simulation, the mesh density is organized globally in the dialog box 'Simulation Parameters'. The mesh density can be defined in the range between 10% and 100%.

    Figure 02 - Simulation Parameters

    However, to increase the calculation efficiency in the wind tunnel area, the program does not generate a mesh with a constant mesh density but automatically generates a finer mesh in the immediate surrounding of the models swept by the wind than in the remaining area.

    The size of the mesh refinement per model is controlled by means of 5 levels of detail in the 'Edit Model' dialog box. The refinement level can be defined here with the steps 0-4.

    Figure 03 - Level of Detail

    By default, the program provides a global mesh density of 20% with a mesh refinement of Level 2 by model. This setting usually results in a network distribution of category A with 300 to 700,000 cells. With this coarse-meshed category A configuration, the program provides a basic display of the flow field and the pressure distribution on the wind-swept model within a very short time.

    Figure 01 - FE Mesh for Solids

    After checking all input data and compression reactions on the model, it is possible to quickly switch to a Category B mesh in the mentioned dialog boxes by increasing the mesh density and the mesh concentration level to determine a qualitatively superior result.

    Using the finer options for mesh consolidation and refinement levels, it is also possible to achieve mesh of the Category C.
    During the development of the RWIND Simulation program, we tested successfully the mesh configurations of this kind (≥ 50 million) on a corresponding computer. However, we do not yet recommend this configuration because the increased accuracy of results gained through this is not in equilibrium with the computer requirement required for this purpose. In the next development phase of RWIND Simulation, we plan to use a customized mesh in the boundary layer to fully use the category C mesh and to offer transient flow models with more accurate turbulence models.  

  • Answer

    If the building envelope is not modeled, the wind load in RWIND Simulation only attacks the surfaces of the members. Elements that would distribute the pressure between them on the members do not exist. In this case, the function "Close Holes" is not suitable for replacing the surfaces. Thus, an automatic transfer of the wind load to RSTAB or RFEM is not possible.

    However, you can model the building envelope in RFEM in a separate model and have it analyzed in RWIND Simulation. The wind pressure can then, for. For example, you can create them manually as load with the load generators. The procedure is shown in the video. 

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First Steps

First steps

We provide hints and tips to help you get started with the main programs RFEM and RSTAB.

Wind Simulation & Wind Load Generation

With the stand-alone program RWIND Simulation, wind flows around simple or complex structures can be simulated by means of a digital wind tunnel.

The generated wind loads acting on these objects can be imported to RFEM or RSTAB.

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