Setup & Analysis of Gear Pump

1. ANALYSIS OF GEAR PUMP USING
ANSYS FLUENT
SAVANI BHAVIK B.

2. INTRODUCTION
 What is CFD?
CFD: A methodology for obtaining a discrete
solution of real world fluid flow problems.
Discrete solution: Solution is obtained at a
finite collection of space points and at discrete
time levels

3. CFD IN A NUTSHELL
 Solving the governing equation of fluid by using computational
methods under various physical conditions (e.g. heat transfer,
radiation, electromagnetic field, nuclear reaction…etc.) to study
different phenomena encountered in the numerous branches of
physical science.

4. CFD APPLICATION
Aerospace
Automotive
Chemical Processing
Polymerization reactor vessel-
prediction of flow separation
and residence time effects.
Marine

5. CFD APPLICATION
Turbomachinery
Semiconductor
Industry
Civil Engineering

6. BUILDING BLOCKS
Geometry & grid
generation module
Problem setting
module
Solution Module
Visualization
Module
What to: Presume
• Boundary / initial conditions
• Physical models
& what to: Neglect
• Physical phenomena (i.e. heat transfer, chemical
reaction…etc)
• Properties (i.e. Compressibility, real gas…etc)
& what to : Calculate
• Unknowns
• Relationships between field variable
Solution methods & algorithms
• Spatial / temporal discretization
schemes
• Convergence criterion
• Interpolation methods

7. METHODOLOGY
 During Preprocessing
 The geometry of the problem is defined
 The volume occupied by the fluid is divided into discrete cells.
The mesh may be uniform or non-uniform
 The physical modelling is defined – for eg. The equation of
motion + enthalpy + radiation + species conservation
 Boundary conditions are defined. This involves specifying the
fluid behavior and properties at the boundaries of the problem.
For transient problems, the initial conditions are also defined
 The simulation is started and the equation are solved
iteratively as a steady-state or transient
 Finally a postprocessor is used for the analysis and
visualization of the resulting solution.

8. FINITE VOLUME METHOD USED IN
DISCRETIZATION
 The finite volume method (FVM) is a common approach used in CFD
codes, as it has an advantage in memory usage and solution speed,
especially for large problems, high Reynolds number turbulent flows,
and source term dominated flows (like combustion).
 In this method the governing partial differential equations are recast in
the conservative form and then solved over a discrete control volumes
and thus guarantees the conservation of fluxes through a particular
control volume.
 Here Q is the vector of conserved variables, F is the vector of
fluxes V is the volume of the control volume element, and A is the
surface area of the control volume element. The finite volume
equation yields governing equations in the form:

9. FINITE ELEMENT METHOD
 The finite element method (FEM) is used in
structural analysis of solids, but is also
applicable to fluids.
 It is much more stable than the finite volume
approach. However, it can require more
memory and has slower solution than the
FVM.

10. FINITE DIFFERENCE METHOD
 The finite difference method (FDM) has
historical importance and is simple to
program.
 It is currently only used in few specialized
codes, which handle complex geometry with
high accuracy and efficiency by using
embedded boundaries or overlapping grids
(with the solution interpolated across each
grid).

11. PURPOSE OF PRESENTATION
GEAR PUMP
 A gear pump uses
the meshing of gears
to pump fluid by
displacement.
 There are two main
variation: external
gear pump and
internal gear pump
 Gear pump are
positive displacement
meaning they pump a
constant amount of
fluid for each
revolution.

12. THEORY OF OPERATION
 As the gears rotate they separate on the intake
side of the pump, creating a void and suction
which is filled by fluid. The fluid is carried by the
gears to the discharge side of the pump, where
the meshing of the gears displaces the fluid.
 Mechanical clearances are small, which
prevents the fluid from leaking backwards.
 Rigid design of the gears and houses allow for
very high pressures and the ability to pump
highly viscous fluids.

13. Internal Gear
Pump
External
Gear Pump

14. PROCESS IN SOLVING PROBLEM
 Set up a problem using the 2.5D dynamic re-
meshing model.
 Specify dynamic mesh modeling parameters.
 Specify a rigid body motion zone.
 Specify a deforming zone.
 Use prescribed motion UDF macro.
 Perform the calculation with residual plotting.
 Post process using CFD-Post.

15. PROBLEM STATEMENT
 The current setup is an external gear pump
which uses two external spur gears.
 Gears rotate at constant rate of 100 rad/s.
 Fluid- oil (Density- 844 kg/m3 & Viscosity –
0.02549 kg/m-s)
 Mass flow rate of fluid in and out of the pump
is of interest.

16. PROBLEM SCHEMATIC

17. MESH

18. PROBLEM SETUP
 General setting- Solver
1. Type- pressure-Based
2. Velocity Formulation- Absolute
3. Time – Transient
 Models- Viscous - Realizable k-epsilon with
standard wall function

19. PROBLEM SETUP
 Material
1. Material – oil
2. Density -844 kg/m3
3. Viscosity – 0.02549 kg /m-s
 Cell Zone conditions
1. Each cell zone, select material as oil

20. PROBLEM SETUP
 Boundary conditions (Inlet and outlet
conditions are set)
1. Inlet- Default Pressure
2. Outlet – Gauge Pressure (101325 Pa)
 Define UDF
1. UDF macro is written for the gear sets to rotate
in opposite directions at constant rate of 100
rad/s
2. UDF is loaded and compiled

21. PROBLEM SETUP
 Mesh Motion Setup
1. Dynamic mesh
 Mesh Method:
 Smoothing
 Remeshing
 Remeshing Method
 2.5D
 Parameters
 Min. Length Scale –
Default
 Max. Length Scale –
Default
 Size Remeshing Interval
- 1
2. Motion of gear 1
 Zone – Gear 1
 Type – Rigid body
 Motion UDF/ profile –
gear1::libudf
 C.G (X,Y,Z)- (0, 0.085,
0.005)
3. Motion of gear 2
 Zone – Gear 2
 Type – Rigid body
 Motion UDF/ profile –
gear2::libudf
 C.G (X,Y,Z) – (0, -0.085,
0.005)

22. PROBLEM SETUP
4. Motion of symmetry-1
gear_fluid
 Zone – sym1-gear_fluid
 Type – Deforming
 Geometry Definition – Plane
 Point on Plane (X ,Y, Z) –
(0, 0, 0.01)
 Plane normal (X ,Y, Z) – (0,
0, 1)
 Meshing Options:
 Methods: Smoothing &
Remeshing
 Zone Parameters
 Min. Length Scale – 0.0005
 Max. Length Scale- 0.002
 Max. Skewness – 0.8
5. Motion of symmetry-2
gear_fluid
 Zone – sym1-gear_fluid
 Type – Deforming
 Geometry Definition – Plane
 Point on Plane (X ,Y, Z) –
(0, 0, 0)
 Plane normal (X ,Y, Z) – (0,
0, 1)
 Meshing Options:
 Methods: Smoothing
 Zone Parameters
 Min. Length Scale – 0.0005
 Max. Length Scale- 0.002
 Max. Skewness – 0.8

23. PROBLEM SETUP
 Dynamic mesh
 Time step size – 5e-6
 No. of steps – 1000
 Integrate
 Preview control
 Time step size – 5e-6
 No. of steps – 1000

24. SOLUTION
 Solution methods
 Retain defaults
 Solution controls
 Relaxation factor of
pressure- 0.4
 Momentum – 0.5
 Turbulent K.E – 0.7
 Turbulent dissipation rate
– 0.7
 Turbulent viscosity – 0.75
 Solution initialization
 TKE – 0.1
 Gauge pressure – 101325
Pa
 Initialize the solution
 Run Solution (Run
calculation for 150 time
steps)
 Time step size- 5e-6
 No. of time steps – 3000
 Max iterations / time step –
40
 Calculate

26. POSTPROCESSING
Velocity
Contour

27. Pressure
Contour

29. CONCLUSION
 The accuracy of the computed flow rate for a
given model increases as the outlet pressure
decreases.