Water immersion single-mirror schlieren imaging system for flow visualization

TL;DR

This paper introduces a compact, water-immersed single-mirror schlieren imaging system that enhances flow visualization sensitivity and reduces system size and artifacts, suitable for in-water and air applications.

Contribution

A novel, small-footprint, water-immersed single-mirror schlieren system that improves sensitivity and reduces artifacts compared to traditional two-mirror setups.

Findings

Water immersion reduces system footprint by 25%.

The system enhances flow visualization sensitivity.

Experimental validation shows effectiveness with transparent solutions.

Abstract

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.