Sloshing effect inside a Gearbox
Introduction:
In fluid dynamics, slosh refers to the movement of the free surface of the liquid inside another object which is undergoing motion. Important examples include propellent slosh in spacecraft, ships, and trucks transporting liquids.
A similar effect is observed in a gearbox. Inside a gearbox, the gears are partially immersed in a lubricant and the lubricant is transported by the gear motion so that the lubricant reaches all the teeth of the gear. This brief report is based on the numerical simulation conducted to visualize the movement of lubricant inside a gearbox. The simulation was carried for two different models with varying clearance between the two gears and with two different liquid, with different properties.
Model Preparation:
In order to save computational time, the given 3D model is converted into a 2D surface with the help of split bodies option in SpaceClaim. The model used for two cases is displayed in the figures. Figure 1 represents the model for the base case and the model used for the second case with increased clearance.
The model is meshed by using triangular elements. The characteristics of the mesh are
summarized in table 1.
After meshing, the model is imported into Fluent solver. Two-phase model is used in the simulation. A region is marked using the mark/adapt cells option to indicate the region where the liquid lubricant is defined. This region is patched with the liquid after initialization. The remaining region is patched with air.
A user-defined function, shown in figure 2, is loaded into the solver to define the motion of gears. The function is linked to the gears through the creation of dynamic mesh zones. The remeshing parameters are defined in such a way that it helps in the smooth redefining of the mesh as the gears move with time.
A transient simulation is conducted to visualize the movement of liquid with time. The parameters used in the solver are listed below
Multiphase mode - Volume of Fluid method
Viscous model - realizable k-epsilon model with Enhanced Wall Treatment
Time step size - 0.0001 s
Number of time steps - 1000.
The study is repeated with two types of fluid, water and oil. The properties of the fluids are shown in table 2.
Results:
The results of the study are summarized in the form of animation videos for both cases, each one, simulated with water and oil.
Video1: Case 1 with Water as Liquid.
Video2: Case 1 with Oil as Liquid
Video3: Case 2 with Water as Liquid.
Video4: Case 2 with Oil as Liquid
Conclusion:
The lubricant is transported by the gears from bottom to the upper portion of the gearbox as it can be observed from the simulation videos. From the results of the simulation, it can be concluded that lubricant takes longer time to reach all the gears, unlike the normal gearbox. Also, it can be observed that oil with higher viscosity was not able to move quickly to all the parts of the gear. The simulation can be extended to include other liquids with a higher viscosity to understand more clearly the effect of viscosity of the liquid to this application.