Quantitative flow visualization by hidden grid background oriented schlieren

TL;DR

This paper presents a novel hidden grid background oriented schlieren technique for quantitative visualization and analysis of natural convection heat transfer, using phase encoding of background pattern distortions.

Contribution

It introduces a new method that encodes refractive index variations in a hidden background pattern for precise quantitative flow visualization.

Findings

Effective visualization of natural convection flows.

Quantitative phase estimation using windowed Fourier transform.

Demonstrated capability to analyze small heat transfer phenomena.

Abstract

The paper introduces hidden grid background oriented schlieren for quantitative study and visualization of natural convection heat transfer. In this technique, the refractive index variation, induced by the temperature gradient, is encoded in the recorded signal phase through the distortion of a background pattern. The background (undistorted) pattern is implicit (or hidden) in the light source. Quantitative estimation of the phase map is obtained by windowed Fourier transform. This method offers localized processing of the signal using joint space-frequency representation. The performance of hidden grid background oriented schlieren is practically demonstrated by investigating natural convective flow, a demanding task due to its comparatively small heat transfer.