( 2016) have shown that it is possible to use a smartphone with a continuous wave (cw-) laser for reliable velocity estimates in a plane. The high frame rates of several hundred Hz captured by modern smartphone cameras enables their use for PIV. 2016) and even for flow visualization by Schlieren techniques (Settles 2018 Miller and Loebner 2016). 2021 Wäldchen and Mäder 2018), for determining fluid properties (Chen et al. 2016), for plant identification in botanical classes (Mäder et al. For this reason, smartphones were already used for physical experiments in classes (Staacks et al. The camera technology is quickly advancing, and the processors will become more and more powerful. However, modern smartphones offer a great selection of different sensors and are easy to use. For these reasons, universities often only offer practical courses for a small number of students in which students may not even be allowed to use and to set up the systems themselves since the equipment is used for scientific projects in parallel. Furthermore, the installation and set up is complex. The costs for this equipment can easily add up to 100,000 euro. Unfortunately, a typical PIV/PTV setup consists of a (double-) pulse laser, a scientific camera and a synchronization device. A recent overview of advanced methods is provided by Kähler et al. Compared to point measurement methods such as laser Doppler velocimetry (LDV) or hot wire anemometry (HWA), the introduction of these measurement techniques has already contributed enormously to a better and more intuitive understanding of flows. 2018 Adrian and Westerweel 2011) or particle tracking velocimetry (PTV) are used for these purposes.īy adding tracer particles to the fluid and measuring their movement with digital camera equipment and advanced evaluation algorithms, these methods provide the possibility to measure velocities in a measurement plane or even a volume. Nowadays, often optical methods like particle imaging velocimetry (PIV) (Willert and Gharib 1991 Raffel et al. This problem is best solved in practical sessions applying flow visualization techniques in wind or water tunnels and directly learn from observations. Due to the nonlinearity of the Navier–Stokes equations, it is difficult to establish an intuitive access to flows. Fluid flows also belong to their daily experiences, however, the education of the basics of fluid mechanics or thermodynamics is sometimes cumbersome. Smartphones considerably changed our behavior and communication in recent years and are used on a daily (or even every minute) basis without any trouble by students. This might further increase the use of modern measurement techniques in industry and education. An analysis of the computational time necessary for the data evaluation showed that with the current implementation the app is capable of providing smooth live display vector fields of the flow. The relative uncertainty was shown to be less than 8%, which is reasonable for quick velocity estimates. Last but not least the app can be applied in the field. Thus, the system is much less complex and costly than typical systems, and our experience showed that students have much less reservations to work with the system and to try different parameters. The second benefit is that the design of the menus follows that of modern camera apps, which are intuitively used. The first benefit is that a PIV system using smartphones and a continuous wave (cw-) laser is much cheaper than a conventional system and thus much more affordable for universities. In this paper, a smartphone application is presented that was developed to lower the barrier to introduce particle image velocimetry (PIV) in lab courses.
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