Journal of Mechanics Engineering and Automation 2 (2012) 256-266 Swirl Jets in Crossflow at Low Velocity Ratios Alexandros Terzis 1 , Charilaos Kazakos 2 , Anestis I. Kalfas 2 , Pavlos K. Zachos 3 and Peter Ott 1 1. Group of Thermal Turbomachinery, EPFL-SCI-STI-PO, Swiss Federal Institute of Technology, Lausanne CH-1015, Switzerland 2. School of Engineering, Aristotle University of Thessaloniki, Thessaloniki GR-54-124, Greece 3. Department of Power and Propulsion, Cranfield University, Bedfordshire MK43 0AL, UK Received: February 11, 2012 / Accepted: February 24, 2012 / Published: April 25, 2012. Abstract: This investigation examines experimentally the behavior of swirled jets produced by axial flow fans blowing into a crossflow at low velocity ratios. The main difference with non-swirl cases is an asymmetry of the dominant kidney vortex and a slight distortion of the jet trace downstream of the injection hole. The effect of jet rotation at relatively low swirl numbers and similar velocity ratios is also investigated by a validated computational analysis tool. The numerical results are analyzed by means of various post-processing procedures, aiming to clarify, quantify and analyze the impact of swirl on the characteristics and the flow domain of a jet in crossflow. In general, swirl introduces an asymmetry in all examined quantities and prevents the penetration of the jet into the crossflow, causing the jet to remain closer to the wall surface. The rotation of the injected fluid results in an imparity of the two parts of the Counter Rotating Vortex Pair (CVP) which is no longer symmetric to the axial centerline plane. High swirl numbers result in the destruction of the CVP and the dominant kidney shape vortex is transformed into a comma shape vortex, rotating close to the wall. Key words: Jet in crossflow, swirl, CFD (computational fluid dynamics). Nomenclature x, y, z coordinates in streamwise, spanwise and normal to the wall direction, respectively d jet diameter R jet radius = d/2 V velocity G momentum flux r velocity ratio y+ non-dimensional wall distance S swirl number Greek θ tangential direction Ω angular velocity ω streamwise vorticity ρ density Subscripts j jet cf crossflow m average value o maximum value Corresponding author: Alexandros Terzis, researcher, research field: gas turbine heat transfer. E-mail: alexandros.terzis@epfl.ch. 1. Introduction Jets In CrossFlow (JICF) are used in a variety of engineering applications. Depending on the jet to cross-stream blowing ratio the resulting flow field can be found in the mixing and dispersion of emitted gases from chimneystacks, in fuel injectors, in Vertical/Short Take-off and Landing aircrafts (V/STOL) as well as in cooling of turbine blades. The main parameter used to describe a jet in crossflow is the velocity ratio, r, which is simplified for incompressible flows as follows: rൌ൬ ρ ౠ V ౰,ౠ మ ρ ౙ౜ V ౮,ౙ౜ మ ൰ ଵ ଶ ൗ ρ ౠ ୀρ ౙ౜ ሱ   ሮ rൌ V ౰,ౠ V ౮,ౙ౜ (1) The practical importance of JICF led to an extensive amount of experimental investigations, where a detailed review can be found in Ref. [1]. In the beginning of JICF research, particular emphasis was given on the structure of transverse jets focusing on the jet trajectory and spreading as well as on the mean velocity field downstream of the jet for various velocity ratios. Authors of Refs. [2-4] concluded that the jet DAVID PUBLISHING D