研究目的
To experimentally demonstrate and visualize three-wave resonance in water surface waves using the Free-Surface Synthetic Schlieren method, ensuring minimal alteration of water properties by avoiding additives.
研究成果
The study successfully demonstrates three-wave resonance in water surface waves using the FS-SS method, with experimental results aligning well with theoretical predictions. The method avoids altering water properties by not using diffusing agents, making it reproducible and cost-effective with commercially available equipment. Future work could optimize resolution and account for surface contaminants.
研究不足
The spatial resolution of the FS-SS method is reduced due to the use of an 8x8 interrogation window in digital cross-correlation, leading to a resolution of 3.22 mm/px. Contamination of the water surface by pollutants over time is unavoidable, which may affect measurements. The method is limited to specific wave frequencies and tank sizes, and deviations occur at lower frequencies due to resolution constraints.
1：Experimental Design and Method Selection:
The study uses the Free-Surface Synthetic Schlieren (FS-SS) method for non-invasive 3D wave height mapping, leveraging lensing effects of surface waves on a random dot pattern. Theoretical models include the gravity-capillary wave dispersion relation and conditions for three-wave resonance.
2：Sample Selection and Data Sources:
Water is used as the medium in a square wave tank with specific dimensions (290 mm x 290 mm interior, 70 mm height). Two speaker-driven wavemakers induce surface waves at specified frequencies.
3：List of Experimental Equipment and Materials:
A square wave tank made of clear acrylic (
4：7 mm thick), wavemaker paddles (acrylic slabs, 70 mm by 100 mm, 35 mm thick), light-emitting diodes for illumination, a GoPro Hero 4 Silver camera, a random dot pattern, and software (PIVlab for velocity field computation, MATLAB for data processing). Experimental Procedures and Operational Workflow:
Set up the wave tank with wavemakers and dot pattern. Capture overhead videos of wave evolution using the GoPro camera at 120 fps and 1280x720 resolution. Compute displacement vector fields using PIVlab, then integrate to obtain wave height gradients and reconstruct 3D surface waves. Perform spectral analysis (temporal and spatial PSD) for specified triad frequencies.
5：Data Analysis Methods:
Use Welch method with Hanning window for temporal spectra, 2D FFT with Hanning window for spatial spectra, and integration of spectra to visualize wave propagation directions. Compare results with theoretical predictions.
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