## Gearbox sloshing effect

Objective:

• To analyse the flow pattern of the fluid inside the gearbox, for two different clearances of the same geometry and each geometry flow is analyzed by two different fluids (Water and Oil) as lubricants.

Gearbox sloshing effect:

• Slosh refers to the movement of liquid inside another object (which is, typically, also undergoing motion), the liquid must have a free surface to constitute a slosh dynamics.
• The dynamics of the liquid can interact with the gears in the gearbox to alter the system dynamics significantly.
• Other examples are:

1. Propellent slosh in spacecraft tanks and rockets (especially upper stages), and

2. The free surface effect (cargo slosh) in ships and trucks transporting liquids (oil                     and gasoline).

3. Liquid motion in a completely filled tank, i.e. without a free surface, as "fuel                         slosh".

User Defined Function (udf) used:

#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]*/
}

Note: First install Visual C++ command prompt, Ansys workbench is opened through Visual C++ command prompt for all cases.

Case 1: GearBox with gears, engaged with small clearance (water is used as lubricant):

Geometry:

Gears engaged with small clearance(Distance between the centres of gears is 115 mm):

2D Gear:

2D Gear Mesh:

SIMULATION SETUP DETAILS:

I. SETUP PHYSICS

SOLVER

Type --> pressure based

velocity Formulation --> Absolute

Time --> Transient

2D space --> planar

Gravity - Tick the check box

Gravitational Acceleration

X (m/s2) = 0

Y (m/s2) = -9.81

MODELS

Viscous --> k-epsilon

k-epsilon Model --> Reliazable

Near-wall Treatment --> Enhanced wall treatment

Multiphase

Model --> volume of Fluid

Formulation --> Implicit

MATERIALS

Create/Edit Materials

Air:

Density = 1.225 kg/m^3

Viscosity = 1.7894e-05 kg/m-s

Water:

Density = 998.2 kg/m^3

Viscosity = 0.001003 kg/m-s

PHASES

List/show all phases

air - Primary Phase

water - Secondary Phase

II USER DEFINED

Functions --> compiled --> Add

select the udf file --> press ok

press Build

III SETUP DOMAIN

MESH MODELS

Dynamic Mesh - Tick Dynamic Mesh

click on create/Edit

Zones Names --> left_gear

Motion UDF/profile --> left_motion

Centre of Gravity location

x(m) = 0

y(m) = 0

click on create

Zones Names --> right_gear

Motion UDF/profile --> right_motion

Centre of Gravity location

x(m) = 0.115

y(m) = 0

click on create

Mesh Methods - Tick smoothing, Layering, Remeshing

settings --> Remeshing-->Parameters

Minimum Length scale (m) = 0.0001

Maximum Length scale (m) = 0.002

click on ok.

Display zone motion

select - Dynamic Face zones(left_gear and right gear)

preview the motion of both gears

close

Refine/Coarse criteria --> cell registers -->New -->Region

Name - hexahedron

Input Coordinates

X min (m) = -0.05612

X max (m) = 0.17112

Y min (m) = -0.0675

Y max (m) = -0.0375

click on save/Display

IV SOLUTION:

INITIALIZATION

Method --> Hybrid

Initialize at t = 0

Patch

Phase --> water

variable --> volume Fraction

Registers to patch -->select hexahedron

value -->1

click on Patch

close

V RESULTS

GRAPHICS

Contour --> New

options --Filled

contours of -->Phases

phase - water

surfaces - select all surfaces

save/Display

close

VI SOLUTION

ACTIVITIES

Create --> solutions Animation

Animation object --> contour-1

click on preview

Ok

RUN CALCULATON

Time step size = 0.0001

No. of Time Steps = 10000

Scaled Residuals:

Gearbox sloshing effect of lubricant(water) through gears with small clearance Animation:

Case 2: GearBox with gears, engaged with small clearance: (Gear oil is used as lubricant):

The Geometry, Mesh and simulation Details are same, but lubricant Materials is to be changed from water to Gear oil.

MATERIALS

Create/Edit Materials

Air:

Density = 1.225 kg/m^3

Viscosity = 1.7894e-05 kg/m-s

Gear oil:

Density = 871 kg/m^3

Viscosity = 0.04006889 kg/m-s

PHASES

List/show all phases

air - Primary Phase

Gear oil - Secondary Phase

Scaled Residuals:

Gearbox sloshing effect of lubricant(Gear oil) through gears with small clearance Animation:

case 3: GearBox with gears, engaged with increased clearance: (water is used as lubricant):

Geometry

Gears engaged with increased clearance(Distance between the centres of gears is 117 mm:

Right Gear is 48.55151 mm from origin X0

Left Gear is -68.44848 mm from origin X0

2D Gear:

2D Gear Mesh:

SIMULATION SETUP DETAILS:

I. SETUP PHYSICS

SOLVER

Type --> pressure based

velocity Formulation --> Absolute

Time --> Transient

2D space --> planar

Gravity - Tick the check box

Gravitational Acceleration

X (m/s2) = 0

Y (m/s2) = -9.81

MODELS

Viscous --> k-epsilon

k-epsilon Model --> Reliazable

Near-wall Treatment --> Enhanced wall treatment

Multiphase

Model --> volume of Fluid

Formulation --> Implicit

MATERIALS

Create/Edit Materials

Air:

Density = 1.225 kg/m^3

Viscosity = 1.7894e-05 kg/m-s

Water:

Density = 998.2 kg/m^3

Viscosity = 0.001003 kg/m-s

PHASES

List/show all phases

air - Primary Phase

water - Secondary Phase

II USER DEFINED

Functions --> compiled --> Add

select the udf file --> press ok

press Build

III SETUP DOMAIN

MESH MODELS

Dynamic Mesh - Tick Dynamic Mesh

click on create/Edit

Zones Names --> left_gear

Motion UDF/profile --> left_motion

Centre of Gravity location

x(m) = -0.06844848

y(m) = 0

click on create

Zones Names --> right_gear

Motion UDF/profile --> right_motion

Centre of Gravity location

x(m) = 0.04855151

y(m) = 0

click on create

Mesh Methods - Tick smoothing, Layering, Remeshing

settings --> Remeshing-->Parameters

Minimum Length scale (m) = 0.0001

Maximum Length scale (m) = 0.002

click on ok.

Display zone motion

select - Dynamic Face zones(left_gear and right gear)

preview the motion of both gears

close

Refine/Coarse criteria --> cell registers -->New -->Region

Name - hexahedron

Input Coordinates

X min (m) = -0.1257721

X max (m) = 0.1058752

Y min (m) = -0.0685

Y max (m) = -0.0375

click on save/Display

IV SOLUTION:

INITIALIZATION

Method --> Hybrid

Initialize at t = 0

Patch

Phase --> water

variable --> volume Fraction

Registers to patch -->select hexahedron

value -->1

click on Patch

close

V RESULTS

GRAPHICS

Contour --> New

options --Filled

contours of -->Phases

phase - water

surfaces - select all surfaces

save/Display

close

VI SOLUTION

ACTIVITIES

Create --> solutions Animation

Animation object --> contour-1

click on preview

Ok

RUN CALCULATON

Time step size = 0.0001

No. of Time Steps = 10000

Scaled Residuals:

Gearbox sloshing effect of lubricant(water) through gears with increased clearance Animation:

Case 4: GearBox with gears, engaged with increased clearance: (Gear oil is used as lubricant):

The Geometry, Mesh and simulation Details are same, but lubricant Materials is to be changed from water to Gear oil.

MATERIALS

Create/Edit Materials

Air:

Density = 1.225 kg/m^3

Viscosity = 1.7894e-05 kg/m-s

Gear oil:

Density = 871 kg/m^3

Viscosity = 0.04006889 kg/m-s

PHASES

List/show all phases

air - Primary Phase

Gear oil - Secondary Phase

Scaled Residuals:

Gearbox sloshing effect of lubricant(gear oil) through gears with increased clearance Animation:

Conclusion:

• The viscosity of water is less than the viscosity of gear oil, sloshing effect is more in case of water as compared to gear-oil.
• Most part of oil is stuck in between gear teeth, but in case of water it tries to settle down.
• Gearbox with less amount of water does not allow to settle down.
• Gearbox with more amount of gear-oil is filled, for effective functioning.

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