CFD Modelling of Rotating Annular Flow Using Wall y+

Abstract

This project establishes a strategy of accurately modeling rotating annular flow of drilling fluid to improve the numerical predication of pressure loss in an annulus. Pressure loss is vital within several engineering applications from HVAC design to oil & gas drilling. By being able to accurately predict this through numerical methods it creates the potential for innovation and efficiency. The project will build on previous recommendation of wall y⁺ by Salim et al. [1] that looked at high Reynolds number turbulent flow for the predication of wall bounded flow. A strategy was established with the aid of the wall y⁺ value to investigate the most suitable turbulence model in ANSYS FLUENT to create a method that will reduce time and costs in the development of drilling tools. Out of 5 turbulence approaches, the k – ω model was found to be the most accurate for a wall y⁺ of less than 5. The k – ε model performed least well and its was observed that there was a direct link between the turbulent intensity found in the annulus and the performance of the turbulence model. The k – ε was found to over predict the turbulent kinetic energy for the mesh set-up and thus contributed to inaccurate results regarding the pressure loss in the annulus. This project, therefore, suggests that a structured mesh with a y⁺ < 5 and the k – ω turbulence model will provide sufficiently accurate data in the investigation of pressure loss in an annulus. This will provide benefit to the industry and to researchers who wish to model this flow situation where experimental data is not available. The strategy can be used by design engineers to create drilling tools and allow them to try more experimental designs, without the need to build expensive and time-consuming prototypes. It may also be used as an investigation tool for researchers wishing to gain a greater understanding of the complex fluid flow that occurs during rotating annular flow.