gearbox sloshing

Gear box Sloshing: -

Sloshing is phenomenon that happens within closed container or when any abject rotate or translate in container that contains fluid.

Gear box sloshing is important phenomenon to study whether proper lubrication is provided withing gearbox or not. Proper lubrication or motion of solid body placed inside closed container can be easily studied using multiphase transient state analysis using ansys fluent.

Geometry: -

3d Model of gearbox is provided which contains two spur gear rotated inside closed container. First step is to create fluid volume inside container by selecting 4 edges.

For simplifying geometry, we need to convert 3D model into 2D model. For that we have created planes at origin of gear.

3D model and fluid volume are split using plane and corresponding face is copied and paste on X-Y plane in new file.

Meshing: -

meshing of 2d Face is done with element size of 0.25 mm and curvature proximity is turned on with min 1 element across gap. Since for dynamic meshing it is necessary to have proper meshing in order to avoid floating point exception error. I have tried with 10 mm, 5 mm to 0.25 mm meshing to overcome floating point exception error.

Named selection for left gear and right gear is done so as to define motion to this geometry using user defined functions.

Solution: - for solving this type of problem we have to select multiphase model with volume of fluid option turned on.in turbulence model we have selected K epsilon model with realizable and enhanced wall treatment option turned on. We have used transient simulation enabling gravity in -y direction activated. Then we have to define the region which is water and which is air. We have used region to mark with diagonal point calculated and they are as below.

We have used user defined function to defined the rotation to left and right gear

Center of rotation for left gear: -0,0

Center of rotation for right gear: -115mm,0

We can use preview mesh motion to check that UDF are assigned properly or not.

We have used hybrid initialization and then patched region marked in earlier case as water. We have used fixed method for calculation with transient time step of 1e-4 and 10000 iteration. I have stopped simulation after 10 % completion of simulation since the solution is taking 5 to 6 hrs to solve problem.

Dynamic meshing setting: -

I have used only smoothing and remeshing option with following figures are change to accommodate properly inside fluid domain.

Less clearance models

No of elements: -316372

No of Nodes: -162345

Water as Lubricant:

Residuals:

Animation: -

Oil as Lubricant:

Residuals:

Animation: -

Large clearance model

Center of rotation for left gear: -(-0.06844,0)

Center of rotation for right gear: (0.04855mm,0)

No of elements: -345042

No of Nodes: -176747

Region to mark as water/oil

Water as lubricant:

Residuals:

Animation: -

Oil as lubricant:

Residuals:

Animation: -

Results and discussion: -

1. From the simulation it is clear that oil is carried away in more amount rather than water since water has less viscosity.
2. More amount oil carried will results in efficient lubrication than water.
3. Large amount of lubricant availability results in resistance to gear movement and less amount will results in less splashing of oil over gears.
4. For proper identification of sloshing gear should rotate 3 to 4 revolutions time.