Shubham Saxena | Searcharxiv

arXiv2026

Water immersion single-mirror schlieren imaging system for flow visualization

Schlieren imaging is a popular optical technique for visualizing flow in transparent media. In-water high-sensitivity flow visualization, using schlieren imaging, is usually performed with a large-footprint two-mirror z-configuration. Here, we present a small footprint, easy-to-implement, single-mirror schlieren imaging system for in-water flow visualization. The same system is capable of high-sensitivity flow visualization in air as well. At its core, our system uses a concave mirror with water immersion. We present theoretical analysis and experimental results to show that this water immersion helps reduce the system's footprint by 25%. Our water immersion-based single-mirror schlieren imaging method additionally reduces mirror surface artifacts, increasing the sensitivity of flow visualization. This technique enables a low-cost schlieren system, as demonstrated experimentally using an inexpensive concave mirror. We also provide the experimental validation of high sensitivity in-water flow visualization for some transparent chemicals or solutions.

physics.flu-dyn↗

arXiv2025

Advanced Knife-Edge free Self-Aligned Colour Schlieren Imaging with Extended Measuring Range

Schlieren imaging is a powerful, non-intrusive method widely used to visualize refractive index gradients in fluid dynamics and heat transfer studies, essential in fields like aerospace engineering, combustion analysis, and supersonic flow visualization. Traditional Schlieren imaging setups employ a knife-edge cut-off to differentiate between deviated and non-deviated light rays, creating contrast. However, this approach requires highly precise alignment and limits both usability and measurement range, restricting accurate observation of high-gradient phenomena such as combustion processes at elevated temperatures. Here, we proposed a simplified Schlieren imaging method that eliminates the knife edge by introducing a novel integration of an extended RGB segmented colour source with a circular aperture. Our approach significantly simplifies alignment, enables colour visualization, and we achieve expanded measuring range by approximately threefold. Experimental validation, involving imaging hot air plumes generated from butane combustion and transparent adhesive tape tests, demonstrate significant improved performance, including enhanced visibility near regions of high temperature gradients, improved edge detection, and precise visualization of large refractive gradients. This simplified yet robust Schlieren imaging approach substantially broadens the scope and ease of application, facilitating detailed investigations of previously challenging fluid phenomena.

physics.optics↗