Pipe CFD and FEA + FSI Simulation

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

TCAE Main Page - Download This Tutorial - CFD Simulation Report - FEA Simulation Report


TCAE tutorial Pipe CFD FEA FSI GUI interface


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:
TCAE tutorial Pipe FSI GUI interface


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.


TCAE TCAD Pipe Components Spiral


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
TCAE Pipe STL inlet outlet wall


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.


TCAE Pipe FEA solid STL


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

IMPORTANT NOTICE: The surface model has to be clean. The principle is 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 the workflow. It sets all the simulation potential and limits. 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.



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.

TCAE Pipe Mesh GUI Graphical Interface

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.
TCAE Pipe Mesh for CFD


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.

TCAE Pipe FEA Mesh GUI Graphical Interface

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.

TCAE Pipe Mesh for FEA


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.

TCAE Pipe CFD setup GUI


  • Simulation type: Stator
  • Time management: steady-state
  • Physical model: Incompressible
  • Number of components: 1 [-]
  • Wall roughness: none
  • Physical model: Incompressible
  • Speed: - [RPM]
  • Outlet: Static pressure 0 [m2/s2]
  • Turbulence: RANS
  • Turbulence model: k-omega SST
  • Wall treatment: Wall functions
  • Turbulence intensity: 5%
  • Speedlines: 1 [-]
  • Simulation points: 3 [-]
  • Fluid: Water
  • Reference pressure: 1 [atm]
  • Dynamic viscosity: 1.0 × 10E-6 [Pa⋅s]
  • Ref density: 996 [kg/m3]
  • CFD CPU Time: 0.1 core.hours/point
  • BladeToBlade: off
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.

TCAE Pipe component graph




Pipe - FEA 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.

TCAE Pipe CFD setup GUI


  • Beam material: Polyethylene (HDPE)
  • Material density: 960 kg/m3
  • Material structure: isotropic
  • Young modulus: 0.9E9 Pa
  • Poisson ratio: 0.46
  • Fixed radius: 0 [mm]
  • Finite element order: second
  • FEA CPU Time: 0.01 core.hours/point


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.

TCAE simulation run interface GUI




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:

CFD Simulation Report


FEA Simulation Report



TCAE Pipe residuals     TCAE Pipe flow rate     TCAE Pipe efficiency     TCAE Pipe efficiency in iterations     TCAE Pipe torque     TCAE Pipe axial force     TCAE Pipe total pressure     TCAE Pipe total pressure    




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.

Pipe flow CFD slice total pressure




Pipe flow CFD streamtraces


Pipe flow FEA impeller stress


Pipe flow FEA impeller displacement

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.



Pipe flow FEA FSI Displacement Animation GIF




Conclusion


• It has been shown how to make a comprehensive CFD & FEA analysis including FSI of the pipe flow in a single one 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 CFD SUPPORT website: https://www.cfdsupport.com/tcae.html

• Questions will be answered via email info@cfdsupport.com.




References

[1] TCAE Manual
[2] TCAE Training



See also other TCAE simulation examples:

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