The Interaction between a Spatially Oscillating Jet and a Crossflow

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Jet in crossflow is a fundamental flow scenario which may be found in several applications such as fuel mixing in combustors, film cooling of turbine blades, or active flow control on wings. The long history of research on this topic provides a comprehensive insight into the fundamental flow field of a steady jet injected into a crossflow. Recently, several studies have been examining spatially oscillating jets emitted by fluidic oscillators in a crossflow. The jets oscillation does not require any moving parts and is solely based on the internal fluid dynamics, which presents one of the main advantages of these devices. In recent years, the effective and efficient application of spatially oscillating jets in crossflow has been impressively demonstrated for mixing enhancement and active flow control. However, despite some suggestions made from rudimentary flow visualizations, the driving mechanisms for the superior performance of spatially oscillating jets are still unknown. However, this information is crucial for a fundamental understanding and a proper optimization process for applications. The three-dimensionality and unsteadiness of this flow field in conjunction with high oscillation frequencies and velocities make experimental and numerical studies challenging. In the proposed work, an experimental study on the fundamental, incompressible flow field of a spatially oscillating jet in interaction with a crossflow is pursued. The jet is emitted by a fluidic oscillator mounted inside a wind tunnel. Flow visualization is used for providing an initial qualitative insight into the flow field. A traversable stereoscopic particle image velocimetry system in combination with established phase-averaging techniques yields the three-dimensional, time-resolved flow field. The quantitative data (e.g., trajectory, vorticity, and flow features) is compared to that of steady jets in crossflow available from the literature. This comparison is expected to reveal commonalities and differences between the flow fields clarifying the driving mechanism for the superior performance and possibly finding new applications. The complexity of this topic requires narrowing down the investigated parameters. In the proposed work, velocity ratio, oscillation frequency, and jet exit angles are selected parameters to be studied. These parameters are chosen due to their importance in flow control and mixing applications. The results will provide the first experimental evaluation of the three-dimensional, time-resolved interaction between a spatially oscillating jet and a crossflow, hence serving as a basis for optimizations in applications, validation of numerical calculations, and future studies inspecting the influence of additional parameters.