Capture method for digital twin of formation processes of sand bars

Abstract

Hydraulic quantities governing the generation of bedforms (formed spontaneously on the bottoms of rivers) have been investigated through geomorphological methods, laboratory experiments, stability analyses, numerical analyses, and other research methods. Recently, numerical analysis has been conducted using fine spatial grids to accurately describe morphodynamics. However, numerical analysis cannot always describe the real phenomena, because it is based on assumptions. One effective way to verify physical assumptions is to compare numerical analysis with actual measurements of equivalent resolution. Measurement data with high resolution enable the construction of a duplicate of the measurement target on a computer called a “digital twin.” To construct a digital twin of the process of bedforms generation and development, geometries of the water surface and the bed surface must be simultaneously measured. We developed and verified a measurement method for the construction of a digital twin during the generation and development of bedforms. The measurement system uses two cameras and a line laser to simultaneously measure the water surface and bed surface. Accurate refraction correction at the water surface is possible by acquiring the shape of the water surface, allowing the bottom shape to be determined by geometric processing. The method provides sub-millimeter-accurate measurements of the water surface and bottom with a spatial resolution of 0.95 cm longitudinally and 0.038 cm transversely in a 12 m × 0.45 m flume and takes only 1 min per measurement. This method can provide measurement results that contribute to the understanding of the generation and development of bedforms.