3D visualization of two-phase flow in the micro-tube by a simple but effective method

TL;DR

This paper introduces a simple optical method using a prism and mirror setup for 3D visualization of two-phase flow in micro-tubes, validated at cryogenic temperatures, enhancing measurement accuracy of flow parameters.

Contribution

The study develops a novel, straightforward optical technique for 3D visualization of micro-scale two-phase flow, including quantitative analysis of image deformation and correction methods.

Findings

Successful visualization at cryogenic temperatures.

Image enlargement of about 20% due to refraction.

Rectangular optical correction reduces image size by 20%.

Abstract

The present study presents a simple but effective method for 3D visualization of the two-phase flow in the micro-tube. An isosceles right-angle prism combined with a mirror located 45^o bevel to the prism is employed to obtain synchronously the front and side views of the flow patterns with a single camera, where the locations of the prism and the micro-tube for clearly imaging should satisfy a fixed relationship which is specified in the present study. The optical design is proven successfully by the tough visualization work at the cryogenic temperature range. The image deformation due to the refraction and geometrical configuration of the test section is quantitatively investigated. It is calculated that the image is enlarged by about 20% in inner diameter compared to the real object, which is validated by the experimental results. Meanwhile, the image deformation by adding a rectangular optical correction box outside the circular tube is comparatively investigated. It is calculated that the image is reduced by about 20% in inner diameter with a rectangular optical correction box compared to the real object. The 3D re-construction process based on the two views is conducted through three steps, which shows that 3D visualization method can be easily applied for two-phase flow research in micro-scale channels and improves the measurement accuracy of some important parameters of two-phase flow such as void fraction, spatial distribution of bubbles, etc..