The aim of this test case is to validate the following parameters of incompressible laminar couette flow in the annular region of two infinite cylinders (one stationary, one rotating):
The presence of both stationary and rotating components in the geometry necessitates the need for distinct representative zones. SimScale provides two options to approach this problem: the Multi-Reference Frame (MRF) method and the Arbitrary Mesh Interface (AMI) method. Briefly stated, MRF uses source terms for coriolis and centrifugal forces to model the rotation, while AMI explicitly ‘rotates’ the appropriate mesh, interpolating values at each iteration over the interface between the fixed and rotating zones. AMI is inherently transient, but MRF allows for cheaper and quicker results. Thus, MRF uses the steady-state simpleFoam solver in contrast to the pimpleDyMFoam solver used by AMI.
The geometry was uploaded on to the SimScale platform, and appropriate meshing techniques used to generate stationary and rotating zones. Simulation results of SimScale were compared to analytical results obtained from methods elucidated in [1].
Import validation project into workspace
The infinite cylinders were modeled as a a slice of their annulus (see Fig.1.). The dimensions are shown in Table 1. The outer cylinder remains stationary, while the inner rotates with an angular velocity of 0.001 rad.s−1
.
The geometry was uploaded on the SimScale platform, and appropriate meshing techniques were employed to generate fixed and rotating zones in the mesh.
Tool Type : OPENFOAM®
Analysis Type : Incompressible (Laminar)
Mesh and Element types :
| Mesh type | Cells in x | Cells in y | Cells in z | Number of nodes | Type |
|---|---|---|---|---|---|
| snappyHexMesh | 100 | 10 | 100 | 100000 | 3D hex |
Fluid:
Kinematic viscosity: 10−5 m2s−1
Boundary Conditions:
For both MRF and AMI the rotating mesh zone is assigned an angular velocity of 0.001rad.s−1
about the y-axis, although it is interpreted differently by the two cases. The velocity and pressure bounary conditions for MRF and AMI have been stated in Table 3.
| Parameter | Inner Wall (A) | Outer Wall (B) | Sides (C) |
|---|---|---|---|
| Velocity | 0.0 ms−1
(Moving wall velocity) |
0.0 ms−1
|
Symmetry |
| Pressure | Zero Gradient | Zero Gradient | Symmetry |
The analytical solution for Taylor-Couette flow is computed from the simplified Navier-Stokes in cylindrical coordinates [1]. The velocity profile is given by:
u(r)=Ar+Br
Here,
A=uoutrout−uinrinrout2−rin2
and
B=uinrin−Arin2
The pressure distribution is given by:
p=A2r22+2ABlogr−B22r2+C
A comparison of the velocity and pressure variation in the radial direction obtained with SimScale (using MRF and AMI) with analytical results is given in Fig.3A and 3B.
Fig.3. Visualization of velocity and pressure (A, B) in the radial direction for MRF and AMI
| [1] | (1, 2) Richard Lueptow (2009), Scholarpedia: Taylor-Couette flow |
This offering is not approved or endorsed by OpenCFD Limited, producer and distributor of the OpenFOAM software and owner of the OPENFOAM® and OpenCFD® trade marks. OPENFOAM® is a registered trade mark of OpenCFD Limited, producer and distributor of the OpenFOAM software.
