*Article* **Analysis of Air–Oil Flow and Heat Transfer inside a Grooved Rotating-Disk System**

**Chunming Li 1, Wei Wu 2,\*, Yin Liu 2, Chenhui Hu <sup>2</sup> and Junjie Zhou <sup>2</sup>**


Received: 18 August 2019; Accepted: 11 September 2019; Published: 18 September 2019

**Abstract:** An investigation on the two-phase flow field inside a grooved rotating-disk system is presented by experiment and computational fluid dynamics numerical simulation. The grooved rotating-disk system consists of one stationary flat disk and one rotating grooved disk. A three-dimensional computational fluid dynamics model considering two-phase flow and heat transfer was utilized to simulate phase distributions and heat dissipation capability. Visualization tests were conducted to validate the flow patterns and the parametric effects on the flow field. The results indicate that the flow field of the grooved rotating-disk system was identified to be an air–oil flow. A stable interface between the continuous oil phase and the two-phase area could be formed and observed. The parametric analysis demonstrated that the inter moved outwards in the radial direction, and the average oil volume fraction over the whole flow field increased with smaller angular speed, more inlet mass flow of oil, or decreasing disk spacing. The local Nusselt number was remarkably affected by the oil volume fraction and the fluid flow speed distributions in this two-phase flow at different radial positions. Lastly, due to the change of phase volume fraction and fluid flow speed, the variation of the average Nusselt number over the whole flow field could be divided into three stages.

**Keywords:** CFD; two-phase flow; volume of fluid; Nusselt number; grooved disk; flow pattern
