Noncanonical Short Hole Jets-in-Crossflow for Turbine Film Cooling

This paper presents a review of research done over the past several years at Purdue on non-canonical jets-in-crossflow. It is a retrospective and an integrative compilation of results previously reported as well as some new ones. The emphasis is on jets emanating from “short” holes, with length-diameter ratios of one or less. A canonical jet-in-crossflow configuration is one in which a fully developed jet issues from a long pipe fed by a large plenum, into a semi-infinite cross flow. The configuration presented here is noncanonical in the sense that jet issues from a short hole and thus the flow is unable to “adjust” to the hole, unlike the case of a long hole in which fully developed pipe flow can be attained. This is motivated by gas turbine film cooling applications. Experimental results acquired with particle image velocimetry will primarily be presented, with some complementary information gained from RANS simulations of the flow. Many different aspects of the problem have been investigated, and in this paper the focus will be on structural features within the hole and in the developing jet and crossflow interaction. A significant result is that the in-hole vortical structures, depending on their sense of rotation, tend to augment or weaken the primary counter-rotating vortex pair. This impacts global features such as jet trajectory and spreading.