Simulation to study Sloshing Effect in the Gearbox
OBJECTIVE:
To perform the simulation for two clearances of the gears using a different fluid (Water and Oil)
3D Geometry Model:
Extracting the volume and splitting the body by creating a plane in the x-y plane, we obtained a 2D geometry of the gears to carry out the simulations.
1. 2D Geometry (less clearance)
2. 2D Geometry (more clearance)
In total, we ran 4 cases- gearbox of different clearances and with the two different fluids.
We have opened the Ansys Workbench through the command prompt to compile the UDF (User Defined Function)
For Setup, Pressure based solver was used with Transient time and Absolute Velocity formulation. Gravitational acceleration was enabled in a negative Y direction.
A volume of fluid volume model was used in Multiphase model with 2 number of Eulerian phases. Implicit formulation method was used to avoid the exceeding courant number with volume fraction cut off of 1e-06.
In Viscous Model, Realizable k-epsilon model was used with Enhance Wall Treatment model. TKE Prandtl number of 1 and TDR Prandtl number of 1.2
For the dynamic Mesh, Smoothing, layering, Remeshing methods were used and dynamic mesh zones were created as left gear and the right gear, obtaining the motion from UDF.
According to the UDF, Omega (Angular velocity) = 200 rad/min
Omega = 2*pi*N/60
From here, N (rpm)= 1909.86. Per second = 31.83 rotations.
For 1 rotation it takes 0.0314s
Managed to get the simulation for 0.093s flow time which is approximately 3 rotations for all the cases.
Properties of Oil:
Density: 871 kg/m^3
Viscosity: 0.04006889 kg/m-s
Less Clearance
Mesh
All triangle method was used with 30 mm element size.
The Region was marked with the following Co-ordinates
X Min (m): -0.05612
X Max (m): 0.17112
Y Min (m): -0.0675
Y Max (m): -0.0375
For Dynamic mesh,
Local Cell Remeshing method was used with parameters as
Minimum Length Scale(m): 1e-05
Maximum Length Scale(m): 0.0002
Maximum cell skewness: 0.4
Size remeshing interval: 2
Case 1 (Water)
Residual Plot
Animation
Case 2 (Oil)
Residual Plot
Animation
Comparison between water and oil used as a fluid in Sloshing for fewer clearance gears
More Clearance
Mesh
All triangle method was used with 10 mm element size.
The Region was marked with the following Co-ordinates
X Min (m): -0.14
X Max (m): 0.175
Y Min (m): -0.089
Y Max (m): -0.0364
For Dynamic mesh, Local Cell Remeshing method was used with parameters as
Minimum Length Scale(m): 0.0001
Maximum Length Scale(m): 0.002
Maximum cell skewness: 0.5
Size remeshing interval: 5
Case 3 (Water)
Residual Plot
Animation
Case 4 (Oil)
Residual Plot
Animation
Comparison between water and oil used as a fluid in Sloshing for more clearance gears
Observation and Conclusion:
In the animation, the fluid at the base gets carried away by the teeth of gears opposite inward motion as defined in UDF.
The gear teeth occupied with the fluid when intersects or meet produces a splash over the above wall case, eventually spreading sideways (left and right). And gradually the fluid rolls down along the case wall curvature downwards following the same process in long duration.
Throughout this process, the lubricating fluid whether water or oil moves throughout the case which helps in the reduction of friction between the gears.
Comparatively, as the viscosity of the oil is greater than that of water, the oil sticks to the wall and gears providing smooth friction functioning during the motion.