A hydraulic jump is a rapid transition from supercritical flow to subcritical flow characterized by the development of large scale turbulence, surface waves, spray, energy dissipation and considerable air entrainment....A hydraulic jump is a rapid transition from supercritical flow to subcritical flow characterized by the development of large scale turbulence, surface waves, spray, energy dissipation and considerable air entrainment. Hydraulic jumps can be found in waterways such as spillways connected to hydropower plants and are an effective way to eliminate problems caused by high velocity flow, e.g. erosion. Due to the importance of the hydropower sector as a major contributor to the Swedish electricity production, the present study focuses on Smoothed Particle Hydrodynamic (SPH) modelling of 2D hydraulic jumps in horizontal open channels. Four cases with different spatial resolution of the SPH particles were investigated by comparing the conjugate depth in the subcritical section with theoretical results. These showed generally good agreement with theory. The coarsest case was run for a longer time and a quasi-stationary state was achieved, which facilitated an extended study of additional variables. The mean vertical velocity distribution in the horizontal direction compared favorably with experiments and the maximum velocity for the SPH-simulations indicated a too rapid decrease in the horizontal direction and poor agreement to experiments was obtained. Furthermore, the mean and the standard deviation of the free surface fluctuation showed generally good agreement with experimental results even though some discrepancies were found regarding the peak in the maximum standard deviation. The free surface fluctuation frequencies were over predicted and the model could not capture the decay of the fluctuations in the horizontal direction.展开更多
The Present work reports the variability of the derived sound channel and its parameters （surface sound velocity, conjugate depth, SLD （Sonic Layer depth） and SOFAR（Sound Fixing and Ranging） depth） has been pres...The Present work reports the variability of the derived sound channel and its parameters （surface sound velocity, conjugate depth, SLD （Sonic Layer depth） and SOFAR（Sound Fixing and Ranging） depth） has been presented over the Bay of Bengal and Arabian Sea. We use World Ocean Atlas Annual data （2013） on temperature; salinity of North Indian Ocean （0°-25°N; 50°-95°E） and its bathymetry have been utilized for the present computation. The depth of the sound channel axis increases towards the northern latitudes in the Arabian Sea, while it decreases in the Bay of Bengal. Coming to the conjugate depth, it shows variation from 120-400 m in the Bay of Bengal and 50-320 m in the Arabian Sea. The range of SLD is varying between 20-40 m in the Bay of Bengal and 10-30 m in the Arabian Sea. The Bay of Bengal and the Arabian Sea have depth limited nature of the profile, i.e. surface sound speed exceeds the near bottom values. This has an important implication in the sound propagation in the SOFAR channel. Anticipated acoustic rays in an ocean with depth limited profile will propagate as surface refracted, bottom reflected （RBR） rays. As a result, the effective sound channel lies much below the sea surface.展开更多
文摘A hydraulic jump is a rapid transition from supercritical flow to subcritical flow characterized by the development of large scale turbulence, surface waves, spray, energy dissipation and considerable air entrainment. Hydraulic jumps can be found in waterways such as spillways connected to hydropower plants and are an effective way to eliminate problems caused by high velocity flow, e.g. erosion. Due to the importance of the hydropower sector as a major contributor to the Swedish electricity production, the present study focuses on Smoothed Particle Hydrodynamic (SPH) modelling of 2D hydraulic jumps in horizontal open channels. Four cases with different spatial resolution of the SPH particles were investigated by comparing the conjugate depth in the subcritical section with theoretical results. These showed generally good agreement with theory. The coarsest case was run for a longer time and a quasi-stationary state was achieved, which facilitated an extended study of additional variables. The mean vertical velocity distribution in the horizontal direction compared favorably with experiments and the maximum velocity for the SPH-simulations indicated a too rapid decrease in the horizontal direction and poor agreement to experiments was obtained. Furthermore, the mean and the standard deviation of the free surface fluctuation showed generally good agreement with experimental results even though some discrepancies were found regarding the peak in the maximum standard deviation. The free surface fluctuation frequencies were over predicted and the model could not capture the decay of the fluctuations in the horizontal direction.
文摘The Present work reports the variability of the derived sound channel and its parameters （surface sound velocity, conjugate depth, SLD （Sonic Layer depth） and SOFAR（Sound Fixing and Ranging） depth） has been presented over the Bay of Bengal and Arabian Sea. We use World Ocean Atlas Annual data （2013） on temperature; salinity of North Indian Ocean （0°-25°N; 50°-95°E） and its bathymetry have been utilized for the present computation. The depth of the sound channel axis increases towards the northern latitudes in the Arabian Sea, while it decreases in the Bay of Bengal. Coming to the conjugate depth, it shows variation from 120-400 m in the Bay of Bengal and 50-320 m in the Arabian Sea. The range of SLD is varying between 20-40 m in the Bay of Bengal and 10-30 m in the Arabian Sea. The Bay of Bengal and the Arabian Sea have depth limited nature of the profile, i.e. surface sound speed exceeds the near bottom values. This has an important implication in the sound propagation in the SOFAR channel. Anticipated acoustic rays in an ocean with depth limited profile will propagate as surface refracted, bottom reflected （RBR） rays. As a result, the effective sound channel lies much below the sea surface.
