CFX Berlin - TwinMesh for cfd analysis of rotary pd machines

TwinMesh for reliable cfd analysis of rotary pd machines

Combining TwinMesh and ANSYS CFX offers engineers a unique, efficient and fast workflow for transient, three-dimensional computational fluid and thermal analyses (cfd) of gerotor pumps, lobe pumps, gear pumps and screw compressors at maximum reliability. Our novel grid generation software automatically generates high quality structured meshes of the rotating parts of positive displacement (PD) machines and eliminates common numerical limits. TwinMesh drives real innovation in the field of PD machines helping engineers to realize a faster time-to-market, higher machine quality, longer durability, and decreasing development costs.

For more information on TwinMesh please visit also our international website www.twinmesh.com or register for our next free webinar on July 9th 2019!

Next Webinar

July 9th 2019

picture gear pump
pressure distribution in a gear pump
Mesh Gear Pump
structured hex mesh for a gear pump
picture meshed gear pump
structured numerical grid for a gear pump
Bild TwinMesh GUI external gear pumps
TwinMesh GUI for gear pumps
Bild TwinMesh GUI Innenzahnradpumpe
TwinMesh GUI for internal gear pumps
Bild: TwinMesh Gerotor Mesh Quality Min Determinant Zoom
Display of mesh quality (min determinant) of a gerotor pump
Bild TwinMesh Gerotor mesh quality MinDeterminant
Display of mesh quality (min determinant) of a gerotor pump
Bild: TwinMesh gerotor mesh quality minAngle zoom
Quality assurance in TwinMesh: Display of min determinants
Bild: TwinMesh Gerotor Quality MinAngle
Quality assurance in TwinMesh: Display of min determinants
Bild TwinMesh Gear Pump Quality Min Determinant Zoom
Quality assurance in TwinMesh: Display of min determinants
Bild TwinMesh Gear Pump Quality Min Determinant
Quality assurance in TwinMesh: Display of min determinants
Bild: TwinMesh Gear Pump Quality Min Determinant
Quality assurance in TwinMesh: Display of min determinants
2D mesh of a lobe pump
Pressure build-up an pulsation in a screw compressor
Bild Video Schraubenkompressor
Pressure build-up an mesh deformation in a screw compressor
CFD-Bild Schraubenverdichter
Results for a screw compressor
Display of velocity, vectors and cavitation in a lobe pump
Bild statischer Absolutdruck Drehkolbenpumpe
Display of static pressure in a lobe pump
TwinMesh - Automatic structured hexahedral meshing for rotating positive displacement machines
Bild Rechengitter Drehkolbenpumpe
2D grid of a lobe pump
BildGerotor pressure in axial clearance
Pressure distribution in axial clearance of a gerotor pump
Bild Geometrie Drehkolbenpumpe
Geometry of a lobe pump in ANSYS DesignModeler
Bild Geschwindigleitsverteilung in einer Zahnradpumpe
Velocity distribution in a gear pump

Geometry & Mesh Generation

Geometry Modelling & Meshing of the Stationary Parts

In order to build up the flow domain, geometry modelling is typically realised with ANSYS DesignModeler or ANSYS SpaceClaim. Additionally, geometry can be imported via 2D sketches and build up via 3D CAD operations. The meshes for the stationary fluid regions, i.e. suction port, pressure port, casing, and the solid regions, can be generated with common meshing tools such as ANSYS ICEM CFD Hexa or ANSYS Meshing in Workbench. Therefore, structured hexahedral meshes are possible or unstructured hybrid meshes consisting of prisms for the adequate resolution of boundary layers and tetrahedrons for the inner parts.

Geometry and flow volume of an internal gear pump
Geometry and flow volume with stator mesh of an internal gear pump
Geometry and flow volume of an internal gear pump with mesh for the stationary parts
Geometry and flow volume of a screw compressor with mesh of the stationary parts
Geometry and flow volume of a screw compressor with rotor mesh

TwinMesh - Automatic Hexahedral Meshing for the Working Chambers of Rotary PD Machines

TwinMesh is a meshing software for PD machines with one or two axially parallel rotors and continuous (e.g. gerotor pumps) or discontinuous (e.g. screw compressors, lobe pumps) rotor geometries. TwinMesh automatically generates high quality structured meshes of the rotating parts of PD machines.

Import of rotor and casing contours is realised as a 2D cross section via IGES format or CSV text files. TwinMesh then generates hexahedral meshes for the changing fluid volumes at user defined rotation angles. Using special smoothing algorithms the programme takes care of a sufficent gap resolution, smooth changes between small gaps and larger chambers and an homogeneous element distribution. The user has full control of the mesh, which is essential for the mesh quality especially in the boundary layer region and in gap flows. The mesh quality can be checked using special tools prior to export of the meshes.

The flow domain of PD machines changes constantly when in operation. Thus, meshes are generated for defined rotor positions. The stored meshes are then used by the CFD solver while running a simulation. The export data of TwinMesh contains all required meshes for a transient flow simulation as well as the required routines for the automatic mesh import while running the simulation. Also, a ready-to-run simulation template is exported by TwinMesh, which enables an immediate start of a flow analysis with ANSYS CFX.

TwinMesh - Automatic structured hexahedral meshing for rotating positive displacement machines
Bild: TwinMesh Gerotor Quality MinAngle
Display of mesh quality (min determinant) of a gerotor pump
Bild TwinMesh Gear Pump Quality Min Determinant
Display of mesh quality (min determinant) of a gear pump
Bild: Rechengitter für die Simulation einer Drehkolbenpumpe
Video: Mesh and solution data for a transient 3D simulation of a lobe pump

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Solver & Post-Processing

Transient CFD-Simulations of Rotary PD Machines with ANSYS CFX

Once all meshes have been generated they can be exported to ANSYS CFX in order to run transient CFD simulations. Within the simulation special user defined Fortran routines are used to import the individual meshes for each time step.

The main advantages of TwinMesh are the flexibility of the meshing methods and the full user control over the quality of the structured meshes, which results in reliable and stable CFD simulations at moderate model sizes. With TwinMesh and ANSYS CFX the user has access to the full capacity of CFD modelling available in ANSYS. Limitations such as for the immersed solid method or the re-meshing approach are redundant with TwinMesh.

Using TwinMesh and ANSYS CFX engineers can:

  • Increase machine performance, efficiency, and durability by a better understanding of complex phenomena inside the machine,
  • Prevent damage caused by cavitation (e.g. gear pumps, gerotor pumps, lobe pumps) or pulsation (e.g. screw compressors),
  • Analyse complex phenomena such as compressible flow behaviour in screw compressors and roots blowers or rheological complex media in gear pumps for polymers,
  • Reduce development costs by use of virtual prototyping.

TwinMesh and ANSYS CFX together make a reliable, modern, and state-of-the-art engineering tool, which allows for analysis and optimisation of PD machines. Simulation results provide essential information such as:

  • Velocity, pressure, and temperature in the whole flow domain,
  • Flow rate, mass flow, pulsation, and machine efficiency (CoP),
  • Torques, moments, and forces,
  • Duration and magnitude of acoustic sources (emission), and
  • Location and magnitude of erosion (caused by particles or cavitation).
Video: CFD result visualization of an internal gear pump
Video: CFD result visualization of an internal gear pump
Video: CFD analysis allows visualisation of pressure and pulsation in a twin screw compressors
Gear pump filling
Video: Visualization of the filling process of a gear pump using a multiphase cfd model in ANSYS CFX and structured meshes from our TwinMesh software

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