Abstract
Image-based particle image velocimetry (PIV) and bubble image velocimetry (BIV) techniques were employed to measure the flow field in both the non-aerated and aerated regions in a steady hydraulic jump. The jump has a Froude number of 4.62 with a large amount of air entrainment. The mean velocities and turbulence properties were obtained by ensemble averaging the repeated measurements. The spatial variations of mean velocity profiles, turbulent intensity, and Reynolds stress were discussed in details. The results show that the ratio between the maximum bubble velocity and the maximum water velocity is almost constant with a value about 0.6. The turbulence intensity of bubbles is very high in the aerated region and reaches about 0.4, while the turbulence velocity of water below the roller is significantly lower. The Reynolds stress is mostly negative and increases as elevation increases. The maximum Reynolds stress occurs at the free surface.
Highlights
A hydraulic jump is a natural phenomenon that is usually seen in a river or downstream of a hydraulic structure such as a sluice gate or a spillway
Liu et al (2004) used acoustic Doppler velocimetry (ADV) to measure velocity, turbulence intensity, and Reynolds stresses in hydraulic jumps and found that turbulence intensity and Reynolds stress have some degrees of similarity
The objective of the present study is to investigate the flow structure in the aerated region of hydraulic jumps using bubble image velocimetry (BIV)
Summary
A hydraulic jump is a natural phenomenon that is usually seen in a river or downstream of a hydraulic structure such as a sluice gate or a spillway. Previous studies on hydraulic jumps can be roughly classified into two categories: the earlier external flow geometry and the more recent internal flow structure. The earlier description of hydraulic jumps mainly focused on the measurement of surface profile and depth-length relation of the jumps (Rajaratnam and Subramanya 1968, Leutheusser and Kartha 1972, Mehrotra 1976). Studies on the internal flow structure of hydraulic jumps have been focused on the velocity field, turbulent characteristics, and void fraction in the jumps. Liu et al (2004) used acoustic Doppler velocimetry (ADV) to measure velocity, turbulence intensity, and Reynolds stresses in hydraulic jumps and found that turbulence intensity and Reynolds stress have some degrees of similarity. Long et al (1990) used LDV to measure the mean velocity, turbulent shear stresses, and turbulence intensity for a submerged hydraulic jump. Studies on the internal flow structure of hydraulic jumps have been focused on the velocity field, turbulent characteristics, and void fraction in the jumps. Rajaratnam (1965) conducted velocity measurements using a pitot tube in a hydraulic jump and concluded that the velocity distribution in a hydraulic jump is similar to that in a typical wall jet. Liu et al (2004) used acoustic Doppler velocimetry (ADV) to measure velocity, turbulence intensity, and Reynolds stresses in hydraulic jumps and found that turbulence intensity and Reynolds stress have some degrees of similarity. Long et al (1990) used LDV to measure the mean velocity, turbulent shear stresses, and turbulence intensity for a submerged hydraulic jump. Lennon and Hill (2006) used PIV to measure mean and turbulent
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
