This study presents an experimental work to analyse the submerged hydraulic jump generated downstream of overflow nappe impinging jets. The overflow structure consists in a sharp-crested weir located at an elevation of 2.20 m from the bottom of the plunge pool. To advance in the understanding of the phenomenon, the velocity field and air entrainment rate were measured with optical fiber and modified Pitot tube in different sections of the submerged hydraulic jump. For the Pitot tube, GE Druck model UNIK 5000 pressure transducers have been used to measure the static and the dynamic pressures. The output signal of both ports was scanned at 20 Hz for 60 s. The optical fiber measurements were carried out with a RBI-instrumentation equipment. Each point was measured during 90 s in the same locations registered by the Pitot tube. The study is focused on the analysis of the local air entrainment concentration, bubble frequency, Sauter mean bubble diameter, mean velocity near the bottom, and free surface undulation pattern.

The researchers express their gratitude for the financial aid received from the Ministerio de Ciencia, Innovación y Universidades and the Fondo Europeo de Desarrollo Regional (FEDER), through the Project “La aireación del flujo en el vertido en lámina libre por coronación de presas a nivel de prototipo y su efecto en cuencos de disipación de energía”, Reference (RTI2018-095199-B-I00). The second author would like to thank the Ministerio de Educación, Cultura y Deporte for the financial aid received from the University Teacher Training Grant (FPU), reference number FPU16 / 05658.