Study of the measurement for the diffusion coefficient by digital holographic interferometry

Area of Science:

• Physical Chemistry
• Fluid Dynamics
• Optical Measurement Techniques

Background:

• Accurate measurement of diffusion coefficients is crucial in various scientific and industrial applications.
• Digital holographic interferometry (DHI) is a powerful technique for observing dynamic processes like diffusion.
• Existing DHI methods often lack detailed analysis of experimental conformity to ideal physical models.

Purpose of the Study:

• To analyze the conformity between experimental measurements and the ideal physical model in DHI diffusion coefficient studies.
• To develop novel data processing methods to address discrepancies observed in DHI experiments.
• To accurately determine the diffusion coefficient of KCl in water under specific conditions.

Main Methods:

• Development and application of two novel data processing methods for digital holographic interferometry.
• Analysis of temporal changes in experimental asymmetry during diffusion.
• Measurement of the diffusion coefficient of potassium chloride (KCl) in water at 0.33 mol/L and 25°C.

Main Results:

• Identified significant asymmetry in experimental DHI measurements, which diminishes over time.
• Determined that the initial diffusion time is not constant throughout the experiment, indicating a deviation from the ideal model.
• Calculated a diffusion coefficient of 1.839×10⁻⁹ m²/s when ignoring asymmetry, aligning with literature values.

Conclusions:

• The study highlights inherent asymmetries in DHI experiments that necessitate advanced data processing.
• A more accurate diffusion coefficient of 2.003×10⁻⁹ m²/s was obtained by considering the time-dependent asymmetry, showing a ~10% increase.
• Experimental data in later stages conform better to the ideal physical model due to decreasing asymmetry.