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This paper presents a novel method for measuring three-dimensional (3D) water surface dynamics in a partially filled pipe. The study on investigation of the 3D free surface dynamics in partially filled pipes is very limited. The method involves tinting the water white with titanium dioxide so that the water surface appears like a solid surface to image-based measuring systems. This method uses a high-resolution projector to project a stochastic pattern of light onto the water surface and uses two high-resolution cameras to capture the pattern on the deformed water surface. The 3D instantaneous water surface fluctuation can be computed from the images captured by the two cameras using a standard Digital Image Correlation algorithm. It is demonstrated that the surface dynamics parameters of turbulent flow in partially filled pipes, including surface fluctuations and surface velocity, can be measured using the projector, high-resolution cameras and DIC algorithm. [ABSTRACT FROM AUTHOR]

This paper describes a spatial measurement technique to measure the free surface of natural fluid flows in laboratory applications. This effective solution is based on “Structure-from- Motion/Multi-view Stereo” (SfM-MVS) photogrammetry and is capable of reconstructing water surface morphology, both at an instant and with a high spatial resolution. The efficiency and accuracy of the method is dependent upon the acquisition of high quality imagery (i.e. sharply focussed, no motion blur) with appropriate multi-frame camera coverage and configuration, and data processing must utilise appropriate camera calibration data. The potential of the technique for developing hydraulic understanding is demonstrated using two contrasting approaches. First, the water surface behind a living vegetation element is analysed along a single transect. Second, the full three-dimensional characteristics of the captured water surfaces are examined using statistical methods which demonstrate surface dissimilarity between vegetated and non-vegetated cases. The technique is transferable to real-world field sites. [ABSTRACT FROM AUTHOR]

Overflow structures built in combined sewer systems are often the source of hydraulic failure during wet weather conditions. Their modelling and particularly that of side weir overflows constitutes a very difficult task both regarding the quantitative and the qualitative aspects. In this paper, a new approach based on the video monitoring concept of these structures is proposed. This study aims at the adjustment of a measuring system able to take into account both spatial and temporal heterogeneity of discharges by digital cameras. In order to achieve this task, a full-scale experiment was carried out. Two lighting systems have been used. The acquired images from the experimental follow-up of the installation, over a period of about 15 months, are analysed. Image processing tools are used to determine the shape of the surface profile on the side weir and to transform image data into numerical data exploitable for modelling. The results were proved very satisfactory. [Copyright &y& Elsevier]

This article addresses the experimental measurement and validation of 3D numerical modelling of the free surface of a storm overflow of a sanitation system. The authors have prepared a model to develop the measurement instrument. The 3D free surface measurement was achieved by means of the structured light projection technique. In practice, the interpretation of the deformation of a fringe pattern projected on the surface of the moving water provided the height of the water. The calculation chiefly relied on extracting the phase ϕ(x, y) of the image by performing a Fourier transform of the input signal I(x, y). The work involved the use of reference planes and correcting the deformation of the images generated by the camera. In order to test the suitability of a 3D hydrodynamic computational code for modelling overflows, the experimental results obtained with the model were used as the reference for a comparison with the modelled free surface. The differences in height observed were less than 5 mm. The system has therefore been found to provide reliable data and to validate the use of 3D computational codes. [Copyright &y& Elsevier]