Creating a validation example for Computational Fluid Dynamics (CFD) is a critical step in ensuring the accuracy and reliability of simulation results. This process involves comparing the outcomes of CFD simulations with experimental or analytical data from real-world scenarios. The objective is to establish that the CFD model can faithfully replicate the physical phenomena it is intended to simulate. This guide outlines the essential steps in developing a validation example for CFD simulation, from selecting a suitable physical scenario to analyzing and comparing the results. By meticulously following these steps, engineers and researchers can enhance the credibility of their CFD models, paving the way for their effective application in diverse fields such as aerodynamics, aerospace, and environmental studies.
In many frame and truss structures, it is no longer sufficient to use a simple member. You often have to consider cross-section weakenings or openings in solid beams. In such cases, you can use the "Surface Model" member type. It can be integrated into the model like any other member and offers all the options of a surface model. The present technical article shows the application of such a member in an existing structural system and describes the integration of member openings.
The goal of using the RFEM 6 and Blender with the Bullet Constraints Builder add-on is to obtain a graphical representation of the collapse of a model based on real data of physical properties. RFEM 6 serves as the source of geometry and data for the simulation. This is another example of why it is important to maintain our programs as so-called BIM Open, in order to achieve collaboration across software domains.
The Steel Joist Institute (SJI) previously developed Virtual Joist tables to estimate the section properties for Open Web Steel Joists. These Virtual Joist sections are characterized as equivalent wide-flange beams which closely approximate the joist chord area, effective moment of inertia, and weight. Virtual Joists are also available in the RFEM and RSTAB cross-section database.
If members aligned in space meet in a node, the local x- or y-axes of the members do not lie in one plane, since the local z-axes are aligned in the plane of gravity.
The dialog box for editing load or result combinations is a non-modal dialog box. This means that after you open this dialog box, you can edit the combinations outside the dialog box as well. For manually defining or editing a combination, a separate dialog box can be opened parallel to the "Edit load cases and combinations" dialog box.
Inserting holes in surfaces is very easy due to the large selection of tools. In order to insert holes or drilling in solids, it is necessary to keep in mind that an opening at the beginning and the end of a continuous hole must be created, as well as a surface that separates the hole from the solids.
RFEM and RSTAB provide various options for entering nodal loads. These implemented features allow the user to define the nodal loads in relation to different components in space.
Warning Regarding Connection to Project
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When opening a model immediately after opening the program, there is a message window asking if you want to create a new project for the model in the Project Manager.
Once you have determined the final tendon geometry in RF‑TENDON, exporting the model to a CAD program can be useful. For this purpose, the module includes the option to export the file in the .dxf file format. You can select the export function by right-clicking the workspace. After selecting the DXF format and the storage location, additional settings can be made.
In RF-/STEEL EC3, you can optimize a cross-section automatically within the design. To do this, select the corresponding cross-section in Table 1.3 or define variable parameters for a welded cross-section.
An individual user‑defined workspace can increase your productivity and make your daily work easier. This is why many users take the opportunity to adjust the toolbars in RFEM and RSTAB and to create their own toolbars containing the most frequently used commands.
In RFEM and RSTAB, you can work with the Project Manager. It allows you to create an entire project structure and to connect it with the folders on the local hard disk.
For a clearer display of the structure, you can display it in different colors. The corresponding selection can be opened by right-clicking the work window.
In the case of open cross-sections, the torsional load is removed mainly via secondary torsion, since the St. Venant torsional stiffness is low compared to the warping stiffness. Therefore, warping stiffeners in the cross-section are particularly interesting for the lateral-torsional buckling analysis, as they can significantly reduce the rotation. For this, end plates or welded stiffeners and sections are suitable.
With the "Convert Area Loads on Openings to Line Loads" function, you can automatically take into account, for example, wind loads applied on windows or other loads applied on non‑bearing structures not represented in the model in openings. You can access this function via "Tools" → "Generate Loads" → "From Area Loads on Openings...."
In cross‑sections created in SHAPE‑THIN, the openings, such as bolt holes, can be modeled by using the elements with zero thickness. The program provides two options for calculating shear stresses in the area of such null elements.
According to Book 631 of the DAfStb (German Committee for Structural Concrete), Chapter 2.4, the structural behavior of ceilings changes if their continuous support by walls is interrupted in areas of openings. Depending on the length of the opening area and the plate thickness, measures are necessary regarding the analysis of the ceiling in the area of the opening.
The proportion of glass used when planning a building is increasing. Open, light-flooded buildings represent the modern art of architecture. However, specialized engineers have to face new challenges during planning. One such example is ceiling-high glass facades loaded by a handrail. The influence of this loading, as well as the calculation of the deformation, are shown in this article.
Since the ultimate limit state of beams in the area of openings is affected, particular attention should be paid to this. In general, small openings can be sufficiently covered by adapting the beam structure to the openings. For big openings, it is necessary to consider and model the area separately.
In theory, an ideal gas consists of freely moving mass particles without extension in a volume space. In this space, each particle moves at a speed in one direction. The collision of one particle with another particle or the volume limitations leads to a deflection and a change in the speed of the particles.
The Steel Joist Institute (SJI) previously developed Virtual Joist tables to estimate the section properties for Open Web Steel Joists. These Virtual Joist sections are characterized as equivalent wide-flange beams which closely approximate the joist chord area, effective moment of inertia, and weight. Virtual Joists are also available in the RFEM and RSTAB cross-section database.
Loading panes of insulating glass due to climatic effects are clearly regulated in DIN 18008. In the case of the corresponding pane geometry, this load type can also govern for the ultimate limit state design. The FE design on the entire structure with the space between panes represented as the volume of a gas provides exact results for the analysis. However, a plausibility check is also becoming increasingly important. This article shows various options for performing these checks.
One of my earlier articles described the Isotropic Nonlinear Elastic material model. However, many materials do not have purely symmetrical nonlinear material behavior. In this regard, the yield laws according to von Mises, Drucker-Prager and Mohr-Coulomb mentioned in this previous article are also limited to the yield surface in the principal stress space.
This article presents a bending beam with a circular opening analyzed using the numerical method. As a reference point, there is an example of a perforated beam from [1]. In our case, the 3D model was simplified to a two-dimensional discretization.
If intersections created in RFEM 4 are opened in an RFEM 5 file, the file management of intersections remains in the old format for compatibility reasons. Thus, the individual partial surfaces of the intersection can be activated or deactivated using only the "Integrated/Components" tab, all partial surfaces can only have the same thickness, and it is impossible to use the separate FE mesh refinement for the individual surface components.