Experimental Validation - DSD Case

Experimental Setup

The experimental validation was carried out in collaboration with Drive System Design Ltd. (DSD). DSD performed a series of experiments taking a single gear and rotating it in an oil sump, while varying the level of the oil and the RPMs. The sketch of the setup is shown in Figure 1 below.
Figure 1. Experimental Test Rig Setup

The rotation speed is changed from 500 to 3000 RPM in increments of 500 RPM. The oil level is varied from 40 to 80 mm, measuring from the axis of the gear.

Numerical Setup

The initial particle arrangement is obtained by directly discretizing the CAD model provided by DSD without any simplification. This results in approximately 8.6 million particles (dx = 1e-3 m) for oil and air phases combined.


Qualitatively nanoFluidX has shown very good agreement with the experiments. Similar flow structures between the experiment and the simulation solution have been observed for every case.
Figure 2. Example of the common flow structure. Observed in both simulations and experiments, noting that the relative height of the oil column being raised is similar.

Most notable qualitative result is the observation of the windage effect in the 80 mm oil level case. In the 80 mm case, the gear is not immersed in the oil sump, but rather hovers over the oil surface with several mm distance. At 3000 RPM the windage effects (motion of the air due to the gear rotation) become prominent and the oil’s surface is disturbed in an oscillatory manner, causing occurrence of high frequency waves. Furthermore, small amounts of oil are carried around the domain by the windage effects, causing visible splashes. This behavior is very well captured by the simulation. Instantaneous time frames can be seen in Figure 3 (experimental) and Figure 4 (nanoFluidX simulation).
Figure 3. Experimental images of the 3000 RPM case at 80 mm oil level . Showing disturbance of the oil surface due to windage effects.

Figure 4. Instantaneous image of the nanoFluidX simulation result for 3000 RPM and oil level of 80 mm. Clearly visible are the waves formed by the windage effects, asymmetry in the wave formation (bottom right part of the image), as well as scattered droplets carried by the air phase.