Structural features and surface heat transfer associated with a row of short-hole jets in crossflow

Surface streak experiments coupled with flow Visualization and numerical si mulations were used to investigate short length-to-diameter injection holes for geometries of interest to the gas turbine industry. The now held resul ts were also related to measured surface heat transfer coefficients in the downstream region of the jets. Geometric surface topology maps inferred fro m "oil and lampblack" surface streak experiments give insights into the flo w held, as well as boundary layer disruption, and ultimately the convective heat transfer coefficient enhancement in the wake region of the jets. A se condary counter-rotating vortex pair (CRVP) with the opposite sense of rota tion as the well-documented main CRVP is present in some configurations and is found to noticeably enhance the attachment event in the wake region and correspondingly enhance the convective heat transfer coefficient. The sepa ration and attachment regions corresponding to the separation and attachmen t of boundary layer fluid brought about by jet-crossflow interaction was fo und to strongly affect the heat transfer on the surface downstream of the j ets. The relative strength of the attachment events, and therefore the effe ct on h, is dependent on the trajectory of the CRVP, presence or absence of the secondary CRVP, and the attachment of crossflow fluid that has acceler ated around the issuing jet. In addition to providing information about the crossflow boundary layer disruption, the surface topological results relat e the signature of the surface shear stress to the coherent flow structures in the flow field being investigated. (C) 2000 Begell House Inc. Published by Elsevier Science Inc. All rights reserved.