Author(s): M. Burgler; R. Schneider; D. F. Vetsch; R. M. Boes; J. Heier; B. Hohermuth
Linked Author(s):
Keywords: Ir-water flows; Multiphase flow turbulence; Conductive phase-detection probe
Abstract: Air-water mixture flows are frequently encountered on hydraulic structures. Typical examples include flood spillways and outlet tunnels of reservoir dams. Accurate measurements of air-water flow properties, such as flow velocities, turbulent stresses, air concentrations, or particle (bubbles/droplets) sizes are important for the understanding and prediction of air-water flows. Conductivity-based phase-detection probes consisting of two needles, each needle representing an electric circuit, are currently the best-practice instrumentation in the field of hydraulic engineering. They are used to measure pseudo-instantaneous one-dimensional velocities, air concentrations and particle chord lengths. Phase-detection probes with four or more needles are frequently applied for measurements in bubbly flows in related research fields of chemical, nuclear or process engineering. They enable measurements of the local instantaneous three-dimensional interfacial velocity vector, potentially yielding the full Reynolds stress tensor. This could contribute to an improved understanding of turbulent transport processes in aerated flows on hydraulic structures. However, the limited stability and large size of existing multi-needle probe designs hinders their use in high-velocity flows. In this paper, we present a novel and robust phase-detection probe design with four sensors consisting of 3-D printed conductive paths on one single needle. Further, we discuss the encountered challenges and lessons learned during the design optimization and the various manufacturing steps of such a probe. A prototype probe was successfully tested in a simple setting, demonstrating a lifespan of up to four hours; however, due to time constraints, the production of additional probes and their application in high-velocity air-water flows could not be realized within the scope of this project., Building on these findings, we outline the remaining hurdles that currently limit its application in high-velocity aerated flows on hydraulic structures.
Year: 2024