# Numerical Study of Coolant Flow Phenomena and Heat Transfer at the Cutting-Edge of Twist Drill
## 1 Introduction
They also found that a modified groove on the flank face resulted in a better lubricant supply, consequently extending tool life by up to 50%. [PERSON] and [PERSON] [11] investigated the flow distribution and coolant pressure variations based on the arrangements of the internal cooling channels and optimized these arrangements using CFD. Their analysis indicated that conventional fluid channel arrangements inadequately supplied cutting-edges with coolant. In contrast, the modification of cooling channels proved to be more effective, reducing surface wear and enhancing tool performance by approximately 36%. In another CFD investigation, [PERSON] et al. [26] characterized the mist flow structure for minimum-quantity-lubrication (MQL) drilling. The study involved the selection of two different channel geometries--circular and triangular shapes. The results revealed that the flow structure concentrated close to the drill centre in the case of circular-shaped channels, whereas it concentrated in the vicinity of the three vertices in triangular-shaped channels. From the literature review it is evident that CFD is an efficient tool to provide better insight into cutting fluid flow and its distribution over the complex drill cutting zone, chip removal, and heat transfer on the surface. These studies have proved that CFD is the most suitable tool for studying fluid flow dynamics and tribology when metrological methods are limited in application, especially in drilling operations where the tool-workpiece interface and behaviour of coolants are not visible [27]. In the broader context of machining processes, tool optimization is one of the most important aspects for ensuring process efficiency [28]. CFD simulations offer a pathway to optimize tool design and identify effective internal cutting fluid channels. However, most of the studies reported in the literature investigating drilling operations are found to be insufficient when it comes in comprehensively addressing coolant flow phenomena and heat transfer at the cutting-edge covering all aspects of the drilling process. Furthermore, the literature review highlights that while researchers have explored various coolant channel arrangements, the design modifications have been somewhat limited, often focusing on circular or triangular shapes. This limitation raises the need for more comprehensive design optimization studies, particularly for dissipating excess thermal load at the cutting-edge in drilling operations. The recognition of improved heat dissipation at the cutting-edge with the presence of a notch at the flank face, connected to the coolant channel exit, highlights the significance of coolant channel design in enhancing fluid flow. With this in mind, the current study aims to elucidate the influence of coolant channel design on fluid flow at the cutting-edge area, and thereby, heat dissipation. This research investigates four distinct drill models, each characterized by different arrangements of coolant channels, under varying operating conditions. Each model, detailed in the subsequent sections, possesses a unique combination of shapes and sizes for the coolant channels. The four models under examination are named as follows: standard model drill, standard model drill with notch, profile model drill, and profile model drill with notch. The CFD approach is employed for analysing the coolant flow phenomena and heat transfer at the cutting-edge of twist drills, designed for deep hole drilling operations. The impact of the coolant channel design, pressure difference on the flow dynamics, and heat transfer at the cutting-edge area are investigated comprehensively.