Gearbox Sloshing Effect using ANSYS FLUENT
Gear Sloshing effect:
Aim: To perform four simulations of the gearbox sloshing effect and compare the results among all the cases.
Case 1. 20% Immersion, Fluid - Engine oil
Case 2. 30 % Immersion, Fluid - Engine oil
Case 3. 20% Immersion, Fluid - n-heptane-liquid(c7h16)
Case 4. 30 % Immersion, Fluid - n-heptane-liquid(c7h16)
Dynamic meshing:
The dynamic mesh model alows you to move the boundaries of a cell zone relative to other boundaries of the zone, and to adjust the mesh accordingly. The boundaries can move rigidly with respect to each other and deform.
The dynamic mesh method should be used if the mesh is deforming , or if the mesh motion is a function of the solution (e.g., the six degree of freedom solver)
An example of steady state dynamic mesh usage:
Consider a rescue drop case shown in figure. The object can be moved in any position in the steady-state solver, after which steady-state analyses can be performed at different object positions.
Initial object position:
Final object position after 40 executions:
Advantages of dynamic meshing:
It can be applied where zone motions (particularly with mesh deformation occurs). This mesh model is vastly helpful in modelling fluid flow in turbomachineries.
Disadvantages of dynamic meshing:
The deformatio of mesh may sometimes be unstable when transient simulations are solved. If the remeshing of cells during deformation is not done correctly, it may lead to deformation below zero cell volume and may give rise to negative volume error in Fluent
Sloshing:
In fluid dynamics, slosh refers to the movement of liquid inside another object (which is, typically, also undergoing motion). However, it has become common to refer to liquid motion in a completely filled tank, i.e. without a free surface, as "fuel slosh"
Is sloshing good or bad:
Usually sloshing effect is one of the reasons of energy dissipation in water tankers, fuel tankers or automobiles but certain devices are being produced that can use this random and usable energy of sloshing into some useful purpose
User-Defined Functions:
The functions hooked to the ANSYS Fluent software that contains parameters or properties or methods or models according to the compliance of the user are called UDF or User-defined functions. The UDF are read by the Fluent either by interpretation or by Compilation. The UDF can be written by the user in C language whih is understood by ANSYS
Simulation in ANSYS Fluent:
Geometry:
The 2D geometry of the spur gears were extracted from a 3D model after carefully filling the gear housing with fluid (mixture of air and gear oil)
Meshing:
Mesh element size = 1 mm
Method: All triangles
Setup:
Fluid : Mixture of Air and Engine oil
Gear speed: 200 radians per second
The VOF model for multiphase solver was used with 2 eulerian phases
Viscous Model used: Turbulent K-epsilon model
The UDF containing motions of the left and right gears was build and compiled in Fluent and the regions containing the fluid were marked. The dynamic mesh model was activated with remeshing method and smoothing options.
The time step size provided was 5e-5 and the simulation was done for one complete revolution of the gears (end time: 0.0314 s)
Results:
Case 1. 20% Immersion, Fluid - Engine oil
Case 2. 30 % Immersion, Fluid - Engine oil
Case 3. 20% Immersion, Fluid - n-heptane-liquid(c7h16)
Case 4. 30 % Immersion, Fluid - n-heptane-liquid(c7h16)