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A Low-Cost, Portable, Smartphone Schlieren Imaging System

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2022 ASEE Annual Conference & Exposition


Minneapolis, MN

Publication Date

August 23, 2022

Start Date

June 26, 2022

End Date

June 29, 2022

Conference Session

Engineering Physics and Physics Division Technical Session 3

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Paper Authors


Keith Stein Bethel University

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Keith Stein is a professor in the Department of Physics & Engineering at Bethel University. He has a Ph.D. in Aerospace Engineering, with past research activities focusing on the modeling of parachute dynamics and fluid-structure interactions. He is currently involved in student-faculty studies utilizing advanced optical and high-speed video imaging techniques to study a number of applications involving compressible flows, shock waves, and thermal convection.

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Grace Riermann

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We introduce a smartphone schlieren imaging system for application in our advanced undergraduate fluid mechanics laboratory. The lab experience is integrated in a junior-level fluid mechanics course through open-ended, project-based learning. The lab seeks to merge ongoing research and academic studies into a productive and engaging experience. Projects are carried out by teams, drawing on the diverse skill sets and interests of the individual team members. Lab experiences are also enhanced by lab proficiency gained by students in previous coursework, such as electronics and physical optics. Over the past decade, numerous student projects have utilized advanced optical techniques to study a number of applications involving compressible flows, shock waves, and thermal convection flows. Most of these studies have been confined to the fluid mechanics laboratory and have relied on expensive equipment including research-grade optics tables, high-end optics and digital video cameras.

The smartphone-based schlieren imaging system provides a low-cost, portable alternative for project-based learning. The system is based on a single-mirror schlieren setup, with the smartphone flash serving as the light source and the smartphone camera as the detector. The light source is positioned near the center of curvature of a concave mirror, which focuses the light on the detector. Adjustable mounts for the smartphone and mirror are 3D printed and secured to a common base, allowing for the apparatus to be relocated as a single, portable system. Schlieren imaging is achieved by cutting off approximately 50 percent of the focused light and the image is sharpened by placing a small aperture in front of the flash. Schlieren images can be recorded by the camera for gas flows with spatial density variations and are the result of the refraction of light between the camera and mirror.

Construction of the smartphone schlieren imaging system is straightforward and accessible to lab groups operating with a very limited budget. All parts are 3D printable or otherwise commercially available and the complete system (with the exception of the smartphone) can be constructed for under $100, excluding the materials for 3D printing, which vary. A parts list and drawings for 3D printable parts will be provided.

This work is supported by the NSF Division of Undergraduate Education (award # 2021157) as part of the IUSE:EHR program.

Stein, K., & Riermann, G. (2022, August), A Low-Cost, Portable, Smartphone Schlieren Imaging System Paper presented at 2022 ASEE Annual Conference & Exposition, Minneapolis, MN.

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