- 2015, Global Digital Central. All rights reserved. Improved film cooling hole geometries and effect of coolant density on film cooling have been a focus since the 1970s. One of the first studies on modifying hole exit to improve film cooling effectiveness and quantifying coolant density effect was from Prof. Goldsteins group. This paper provides an overview of the development and implementation of hole exit geometries as well as coolant density study over the past few decades and the impact on future studies of advanced hole geometries under realistic engine-like coolant-to-mainstream density ratio conditions. This work is not intended to be a comprehensive review of the literature.