Gearbox Sloshing effect
Flow of fluid inside a gearbox due to motion of gear.

Step 1: Simulation Setup
For this challenge we are running 4 cases of gearbox with two different clearances and with the two different fluids and observe the flow pattern of the fluid inside the gearbox.
3D Model :
For finding the result using this 3D model is increase the computational cost and time to run the simulation and also we are having Academic license so some limitations for mesh generation. So we are extracting 2D model from 3D model and done simulation on it.
For performing this simulation we have two types of model
Model 1 : Low clearance
Model 2 : High clearance
Meshing :
For refining the mesh for this case we are using all triangle method
 Element size = 30 mm
 Capture proximity ON
 Proximity minimum size = 0.3 mm
 Number of cells across gap = 1
Low clearance
High clearance
So, now we have two fluid for running the simulation. Properties of fluid defined below.
1) Water
 Density = 998.2 kg/m^3
 Viscosity = 0.001003 kg/ms
2) User defined (Oil)
 Density = 871 kg/m^3
 Viscosity = 0.04006889 kg/ms
UDF  User Defined Function
For giving the motion to both the gear we have user defined function. Clockwise motion provided to right gear and Antilockwise motion provided to left gear.
#include "udf.h"
DEFINE_CG_MOTION(right_motion, dt, vel, omega, time, dtime)
{
vel[0] = 0.0;
vel[1] = 0.0;
vel[2] = 0.0;
omega[0] = 0.0;
omega[1] = 0.0;
omega[2] = 2.0e2; /* [rad/s]*/
}
DEFINE_CG_MOTION(left_motion, dt, vel, omega, time, dtime)
{
vel[0] = 0.0;
vel[1] = 0.0;
vel[2] = 0.0;
omega[0] = 0.0;
omega[1] = 0.0;
omega[2] = 2.0e2; /* [rad/s]*/
}
Simulation Setup :
First of all we added the UDF to the ANSYS so we can provide motion to the gear.
Setting up the physics for Gearbox sloshing in ANSYS fluent.
 For this case we are using pressurebased transient solver
 Velocity formulation  Absolute
 Gravity Acceleration
 Xdirection = 0 m/s^2
 Y direction = 9.81 m/s^2
For this case make sure dynamic mesh is ON
 Method for dynamic mesh = Smoothing, Layering, Remeshing
 Remeshing methods = local mesh
 Minimum length scale = 0.0001
 Maximum length scale = 0.002
 Maximum cell skewness = 0.7
 Size remeshing interval = 5
 Dynamic mesh zones
 right gear  right motion
 left gear  left motion
Center of Gravity Location
For Low clearance
 Left Gear
 Xdirection = 0 m
 Y direction = 0 m
 Right Gear
 Xdirection = 0.115 m
 Y direction = 0 m
For High clearance
 Left Gear
 Xdirection = 0.0684485 m
 Y direction = 0 m
 Right Gear
 Xdirection = 0.0485515 m
 Y direction = 0 m
For creating the fluid region inside the gear box we have option inside the adapt and refine and select for region inside cell registers.
For Low clearance
 Option  Inside
 Type  Quad
 Diagonal end point = (0.17112 0.0375 0)
 Diagonal start point = (0.05612 0.0675 0)
For High clearance
 Option  Inside
 Type  Quad
 Diagonal end point = (0.11193 0.03 0)
 Diagonal start point = (0.13182 0.0675 0)
Multiphase model setup
 Model  Volume of fluid
 Volume fraction parameters  Implicit
 Volume fraction cutoff = 1e06
 Interface modeling type  Sharp
For solution we use patch command in initialization
 Phase  Water/Oil
 Variable  Volume fraction
 Value 1 for Water/Oil surface
Run calculation : Same for all the cases
 Time stepping method = Fixed
 Time step size = 0.0001 s
 Number of time steps = 2000
 Maximum iteration/time steps = 20

Step 2: Result
Case 1 : Gearbox with Low clearance and Water as a fluid
Fig : Residuals plots
Fig : Volume fraction of Fluid at initial state.
Animation : Flow of lubricant fluid inside gearbox
Case 2 : Gearbox with Low clearance and Oil as a fluid
Fig : Residuals plots
Fig : Volume fraction of Fluid at initial state.
Animation : Flow of lubricant fluid inside gearbox
Case 3 : Gearbox with High clearance and Water as a fluid
Fig : Residuals plots
Fig : Volume fraction of Fluid at initial state.
Animation : Flow of lubricant fluid inside gearbox
Case 4 : Gearbox with High clearance and Oil as a fluid
Fig : Residuals plots
Fig : Volume fraction of Fluid at initial state.
Animation : Flow of lubricant fluid inside gearbox
Conclusion : 
 As shown by above Animation, we can see that both oil and water can work as a proper lubricant.
 All the teeth of the gears are covered in the lubricant after they completed 1 revolution.
 The difference between oil and water as a lubricant is that there is little sloshing with oil on the top of the gear teeth than water due to its higher viscosity and higher resistance.
 Oil has lower density then water means oil has lower mass per volume so it stick on teeth of gear for more time.
 The splashing in the top half of the gearbox is lesser for the high clearance model because there is much space between the gear to pass the lubricant through.