Gearbox Sloshing Effect Simulation

Question :

We are going to simulate the (2D) gearbox, the most important part in automobile transmission system as it holds gears.

Simulation procedure :

Geometry :

• First we need to import the gearbox geometry

• Then we have to extract the fluid volume.
• After extracting create planes and split the body to get the 2D geometry for the simulation.

• This completes geometry part.

Mesh

• open the mesh and name the required parts

• After naming, mesh the body (in our case we are going to use 0.001 m mesh element size).

• Make the mesh as triangular mesh and turn on the capture proximity.
• This completes the mesh section.

Setup

• Perform the mesh check.
• We will go with transient approach as we need results w.r.t time.
• Put on the gravity.
• Add viscous model and multiphase model.
• Add material as required and list down the phases.
• Add UDF to give motion to gears. We need to start the workbench with visual studio cross tool command prompt.
• Go back in domain section and use adapt cells to add fluid region.

20% region immersed in fluid

Co-ordinates

X-min	Y- min	X- max	Y-max
-0.0675 m	-0.0405 m	0.25 m	-0.07 m

30% region immersed in fluid

Co-ordinates

X-min	Y- min	X- max	Y-max
-0.0675 m	-0.027 m	0.25 m	-0.07 m

• Also add dynamic mesh setting's parameters for the dynamic cells.
• Add dynamic mesh zones for both left and right gear.
• Create a contour to view the phase if correct or not. then add solution animation and simulate the problem for number of timesteps.

Result

• Make volume fraction visible and create a timestep animation to view the gearbox sloshing.

This completes our gear box simulation.

Mesh Inputs:

1] Mesh element size : 0.001 m

2] Mesh : Triangular

3] Elements : 28327

4] Nodes : 15875

Setup Inputs:

1] Viscous Model : k-Epsilon(Standard)

2] Multiphase model : volume of fluid (Implicit)

3] Material : Engine oil and n-heptane(c7h16).

4] Dynamic mesh methods : Smoothing and Remeshing

Remeshing parameters :

• minimum length scale : 0
• maximum length scale : 0.008
• maximum cell skewness : 0.5
• Size remeshing interval : 3

5] Solution method : SIMPLE (first order upwind)

6] Initialization : hybrid

7] Timestep size : 5e-5

We are going to simulate 4 cases 2 with engine oil and 2 with n-heptane(c7h16).

Output :

Part 1

########################## { CASE I - 20% region immersed in engine oil } ##########################

• Residual

Time steps	flow time
2250	0.1125

• sloshing animation

########################## { CASE II - 30% region immersed in engine oil } ##########################

• Residual

Time steps	flow time
2500	0.1250

• sloshing animation

######################## { CASE III - 20% region immersed in n-heptane(c7h16) } ########################

• Residual

Time steps	flow time
2250	0.1125

• sloshing animation

######################### { CASE IV - 30% region immersed in n-heptane(c7h16) } #########################

Time steps	flow time
2250	0.1125

• sloshing animation

Observations:

• Mesh play vital role for a proper simulation of sloshing effect
• Engine oil lubicrates more no. of teeth as it is highly viscous compared to n-heptane.
• 30% fluid immersed gearbox's more no. of teeth are lubricated than 20% fluid immersed gearbox.
• Also n-heptane settles down faster compared to enigne oil as it is less dense and viscous.
• 20% immersed n-heptane's gearbox teeth run without lubrication at 3rd -4th rotation of gears as the fluid has higher velocity resulting in more sloshing
• Density and viscosity plays important role in lubricating the teeth.

Part 2

1] Dynamic meshing :

• Dynamic meshing is the meshing technique used to simulate the flow where geometry changes w.r.t time. It is used when geometry is changing continuously while simulation is going on.
• There are 3 dynamic mesh methods i.e. Smoothing, Layering and Remeshing.
• Each one of them include their own parameters which needs to be set correctly to avoid dynamic meshing error.

Examples:

• Any solid object dropping in a fluid.
• IC engine's piston movement.
• simulation of a turbine wheel.

These are the examples where dynamic meshing can be used.

2] Fluid Sloshing effect:

• fluid sloshing means movement of a fluid inside an enclosed container which is subjected to a motion.
• As they are partially filled which may result in sloshing effect causing rollover, imbalance.
• Fluid sloshing effect can cause damage to container as it may impact on cantainer walls due to fluid instablity caused by movement of the container.
• Example : A water conatiner carrying water is open and when the vehicle is subjected to instabilities will cause water to spill out. This is caused by sloshing effect, as the fliud is ustable to motion of vehicle.

3] UDF :

A UDF is a C program that can be dynamically loaded with ANSYS FLUENT to enhance its standard features.

UDF can be used for a number of applications like :