Region Of Turbulent Jets Research Articles

Validation of the Computational Aeroacoustic Simulation of a Subsonic Jet tailpipe Flow Noise

A case study in the application of computational aeroacoustics in the prediction of flow noise from a subsonic jet generated at the tailpipe of a straight pipe. The simulation is completed using a hybrid approach. The results from a Large Eddy Simulation completed using are used to formulate acoustic sources. These acoustic sources are formulated using Lighthill's analogy and then mapped onto an acoustic finite element mesh using the tools built into the acoustic FEM software Actran. The total predicted sound power of the sources inside the pipe and the turbulent jet region are then validated to completed acoustic measurement using the University of Kentucky's muffler flow test rig.

Retrofitting Vertical Slot Fish Pass with Brush Blocks: Hydraulics Performance

The mean and turbulent flow characteristics of a vertical slot fish pass, with and without brush blocks, were investigated at the Cataloluk Small Hydropower Plant on the Tekir River, located in the Ceyhan River Basin of Turkey. Within the scope of the project, three-dimensional velocity measurements were performed at different hydraulic conditions. The prototype flow measurements showed that by placing brush blocks and the substrate in the vertical-slot pool: (i) the maximum velocity observed downstream of the slot was reduced by 39%; (ii) the maximum lateral component of the Reynolds shear stress observed in the slot region was reduced by a factor of 3; and (iii) the spatially averaged resultant velocity was reduced by 20%. With brush blocks, the turbulent jet region was reduced and recirculation regions disappeared. Furthermore, the spatially-averaged lateral component of the Reynolds shear stress was 3.3 times higher than the spatially-averaged streamwise component of the Reynolds shear stress because of the lateral velocity gradient and mixing in the pool. The present findings will contribute to potential improvements in the non and less efficiently-functioning vertical slot fish pass and other fish pass types by adding brush blocks.

Experimental study on a steam-driven turbulent jet in subcooled water

This study was designed to investigate the behaviour of a steam-driven turbulent jet in subcooled water. The total pressures along the axis of the jet were measured under various steam mass fluxes, water temperatures and nozzle sizes. The results indicated that the lifting-pressure coefficient decreased with inlet steam pressure and water temperature, and an optimal lifting-pressure coefficient could be obtained at pressure ratio 0.228. Then an empirical correlation based on the influencing factors was given to fit the position of the maximum pressure. Moreover, the velocity profiles in the turbulent jet region were obtained, and the results showed the self-similarity property of the velocity profiles. An empirical correlation was suggested to correlate the jet half width obtained from the velocity profiles.

Effect of heart rate on centerline velocities of pulsatile intracardiac jets: an in vitro study with laser Doppler anemometry and pulsed Doppler ultrasound.

This article confirms a recently developed distal jet centerline technique for noninvasively quantifying regurgitant cardiac valve flows. The basic principle that allows flow rate to be calculated is conservation of momentum. As the jet entrains more mass, its centerline velocity decays inversely with distance from the orifice. Under pulsatile flow conditions, it has been shown that this technique remains applicable at peak flow for a normal resting adult heart rate of 60 to 70 beats/min. It is, however, conceivable that at higher heart rates, the same inverse relation between centerline velocity and distance is never fully established, because there is a finite time interval required for the jet to penetrate the receiving chamber. Therefore, the purpose of this study was to determine whether the inverse relationship of centerline velocity to distance develops sufficiently rapidly so that quantitative techniques based on that decay would be applicable over a wide range of heart rates. Two different techniques, an engineering tool, laser Doppler anemometry, and a clinical tool, Doppler ultrasound, were used for measuring jet centerline velocities (averaged over multiple beats). Physiologic pulsatile flows were pumped through two circular orifices, 4 and 6 mm in diameter, at 60 to 150 beats/min; peak orifice velocities ranged from 2 to 5 m/sec. Steady flow experiments were also performed with the same orifice diameters and over the same velocity range. Peak centerline velocities in the fully developed turbulent jet region decayed inversely with distance at all heart rates studied. With laser Doppler anemometry, the proportionality constant of the decay curve was found to be in the range 6.4 +/- 0.5. The pulsed Doppler results provided a jet constant in the range 6.7 +/- 0.3 with the 4-mm orifice diameter, whereas the constant was 6.5 +/- 0.3 with the 6-mm orifice diameter. In steady flow, the proportionality constant was found to be 6.1 +/- 0.2. Therefore, within a wide range of physiologic heart rates, full jet development occurs with sufficient speed so that the expected centerline velocity decay is established (jet empirical constant of 6.3). The conservation of momentum technique for calculating orifice flow rate on the basis of these centerline velocities is thus applicable under physiologic conditions.