High speed cameras for time-resolved laser based turbulence measurements

点击翻译按钮获取中文摘要

This RTI application will give fluid dynamics researchers within the McGill Mechanical Engineering Department the ability to obtain time-resolved measurements of all three velocity components, which is paramount for a deeper physical understanding of turbulent flows and fluid dynamics in general. Obtaining such measurements within a spatial plane provides greater insight into the dynamical aspects of the flow field, such as the dynamics of coherent structures and the spatial evolution of the flow field, which are crucial for the development of flow control strategies and models that aim at reducing the environmental impact of the aerospace and transportation sectors, the dispersion of pollutants within the atmosphere and energy harvesting from wind and water turbines, all of which are strategic research areas within McGill and NSERC. A common experimental method that facilitates this is the optical method of particle image velocimetry (PIV). This technique is non-intrusive which, in its simplest form, requires a flow to be seeded with particles that are illuminated with a laser light sheet; a camera is used to obtain images with a fixed time difference and hence velocity information is extracted by analysing the movement of the particles between two successive images. Using a single camera one obtains two velocity components (planar PIV), however, for all three velocity components one would need two identical cameras (stereo PIV). The department currently has a Dantec time-resolved planar PIV system and it is proposed that this system be upgraded to a stereo-PIV system, which will allow researchers to take time-resolved measurements of all three velocity components within a plane. Having two cameras also allows for other advanced measurements such as joint planar laser induced fluorescence (PLIF) and PIV measurements (stereo-PIV plus PLIF measurements obtained using current camera), extended field of view PIV measurements (two cameras in a side-by-side arrangement), multiscale turbulence measurements (two or more cameras focusing on the same plane with different magnifications) and combined digital image correlation (DIC) and PIV measurements to investigate fluid-structure interactions. A number of projects have already been identified for the proposed equipment, including long and short wave instability of vortex pairs, evolution of vortex rings, decay of multiscale generated wing-tip vortices and flow through a synthetic model (or phantom) of the human larynx during phonation. The PI will offer special training courses for these measurement techniques, which will be made available to HQPs across the department and faculty. The PI alone anticipates at least ten HQPs to be trained on this equipment over the next five years; one undergraduate student has already started their project whilst two PhDs will begin in January 2017, thus highlighting the urgent need for the equipment.