Pipe

Pipe CFD & FEA + FSI Simulation

This report presents a simple tutorial of pipe flow CFD and FEA + FSI analysis using TCAE simulation software.

Introduction

This study shows a pipe flow CFD & FEA analysis, including FSI. The simulation software used for this analysis is TCAE – a comprehensive simulation environment based on open-source. This particular pipe tutorial is completely artificial, and it is used mostly for the training purposes because it is reasonably quick. The goal of this study is to show how to work within TCAE environment.

Pipe Design

A typical input for a detailed simulation analysis is a watertight (wet) surface model in form of an STL surface. For CFD simulation, it is needed to have a closed watertight model (sometimes called waterproof, or model negative, or wet surface) of the model inner parts where the air flows. For FEA simulation, it is needed to have a closed surface model of the solid of the impeller in form of a single one STL surface. The pipe is virtually fixed at its beginning (inlet) so the pipe has a free end that can move due to the pipe flexibility and forces acting on the inner surface of the pipe.

In general, there are multiple ways how the pipe model can be created. The CAD model of the pipe can be generally created in any CAD software manually or in an automated way via parametric model. The particular surface model of this pipe was created in Salome preprocessing platform. Let’s consider the following pipe geometry:

Pipe - CFD Preprocessing

For CFD simulation it is best to split the model into several waterproof components because of rotation (some parts may be rotating and some parts may not). Each component consists of a few or multiple STL surfaces. It is smart to split the surface model into multiple surfaces because it opens a wider range of simulation methods (mesh refinements, manipulation, boundary conditions, evaluation of results on model parts, …). This particular pipe tutorial has just one component.

The model topology is always up to the user, there are no limitations on the number of components or individual surfaces. In any case, the final model for CFD simulation needs to be split into closed waterproof components. Each component consists of individual STL files. Typically, they are the inlet, the outlet, and the wall. For example, within a simplest possible approach, the impeller component can consist just out of three STL surfaces called, for instance:

  • pipe-inlet.stl
  • pipe-outlet.stl
  • pipe-wall.stl
For more details, see the TCAE documentation. Now the CFD model is ready for meshing with TMESH using snappyHexMesh open-source application.

Pipe - FEA Preprocessing

For FEA simulation, it is best to create a simple, single one, closed STL surface of the solid, for instance pipe-solid.stl.

Now the model is ready for meshing with TMESH using NetGen open-source application.

IMPORTANT NOTICE ON PREPROCESSING

The surface of the simulation-ready model has to be clean, simple enough but not simpler! The principles are always the same: the watertight surface model has to be created; all the tiny, irrelevant, and problematic model parts must be removed, and all the holes must be sealed up (the watertight surface model is required). The preprocessing phase is an extremely important part of each simulation workflow. It sets up all the simulation potential and limitations. It should never be underestimated. Mistakes or poor quality engineering in the preprocessing phase can be hardly compensated later in the simulation phase and postprocessing phase. For more details, see the TCAE documentation.

Pipe - CFD Meshing

The computational mesh for CFD is created in an automated software module TMESH, using the snappyHexMesh open-source application. All the mesh settings are done in the TCAE GUI.

For each model component, a cartesian block mesh is created (box around the model), as an initial background mesh, that is further refined along with the simulated object. Basic mesh cell size is a cube defined with keyword “background mesh size”. The mesh is gradually refined to the model wall. The mesh refinement levels can be easily changed, to obtain the coarser or finer mesh, to better handle the mesh size. Inflation layers can be easily handled if needed. For more details, see the TCAE documentation.

Pipe - FEA Meshing

The computational mesh for FEA is created in an automated software module TMESH, using the NetGen open-source application. All the mesh settings are done in the TCAE GUI.

The closed STL model is meshed with just a little effort because there are just a few parameters to set. The most important parameters for FEA meshing are “h Max” and “h Min” which mean the maximal and minimal mesh edge in meters. The mesh is created with an automated algorithm. For more details, see the TCAE documentation.

Pipe - CFD Simulation Setup

The CFD simulation is managed with TCAE software module TCFD. Complete CFD simulation setup and run is done in the TCFD GUI in ParaView. TCFD uses OpenFOAM open-source application.

Any project simulated in TCFD has its component graph. The component graph shows how the components are organized – the model topology. What is the inlet, the outlet and how the components are connected via interfaces. A simple scheme of the component graph is shown below.

Pipe - CFD Simulation Setup

The FEA simulation is managed with TCAE software module TFEA. Complete FEA simulation setup and run is done in the TFEA GUI in ParaView. TFEA uses Calculix open-source application.

Pipe - TCAE Simulation run

The TCAE simulation run is completely automated. The whole workflow can be run by a single click in the GUI, or the whole process can be run in the batch mode on a background. Modules used are TMESH, TCFD, and TFEA. The simulation is executed in the steady-state mode. TCFD includes a built-in post-processing module that automatically evaluates all the required quantities, such as efficiency, forces, force coefficients, flow rates, pressure, velocity, and much more. All these quantities are evaluated throughout the simulation run, and all the important data is summarized in an HTML report, which can be updated anytime during the simulation, for every run. All the simulation data are also saved in tabulated .csv files for further evaluation. TCFD is capable of writing the results down at any time during the simulation. The convergence of basic quantities and integral quantities is monitored still during the simulation run. The geometry was created onetime using TCAD in the preprocessing phase. First, the TMESH is executed to create the volume meshes for CFD & FEA. Then the CFD simulation is executed and evaluated. After that, in the FSI step, the pressure field is integrated to create the force field which is prescribed as a load for the FEA simulation. Finally, the FEA simulation is executed and evaluated.

Pipe - Postprocessing - Integral Results

The simulation results are evaluated automatically. Every simulation run in TCAE has its own unique simulation report. The integral results both for CFD and FEA are written down in the following HTML or PDF reports:

Pipe - Postprocessing - Volume Fields

All the integral results are stored in the .CSV files and are available for further postprocessing if needed. The volume fields are postprocessed in open-source visualization tool ParaView. ParaView provides a wide range of tools and methods for CFD & FEA postprocessing and results’ evaluation. There are available countless useful filters and sources, for example: Calculator, Contour, CLip, Slice, Threshold, Glyph (Vectors), Streamtraces (Streamlines), and many others.

Results Animation

Below, there is an animation of the pipe deformation due to the fluid flow forces acting on the pipe inner surface. The deformation movement is displayed 10 times higher to enhance the details.

Conclusion

  • It has been shown how to make a comprehensive CFD & FEA analysis including FSI of the pipe flow in a single automated workflow.
  • TCAE showed to be a very well-suited tool for CFD, FEA, and FSI engineering simulations.
  • More information about TCAE can be found on the CFD SUPPORT website: https://www.cfdsupport.com/tcae.html
  • Questions will be answered via email info@cfdsupport.com.

Download TCAE Tutorial - Pipe

File name: pipe-TCAE-Tutorial-21.09.zip

File size: 1 MB

Tutorial Features: CFD, FEA, FSI, TCAE, TMESH, TCFD, TFEA, SIMULATION, PIPE, INCOMPRESSIBLE FLOW, DEFORMATION, DISPLACEMENT, STRESS, MODAL ANALYSIS, INCOMPRESSIBLE, RANS, AIRFLOW, STEADY-STATE, AUTOMATION, WORKFLOW

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