Bubble size characteristics in the wake of ventilated hydrofoils with two aeration configurations Karn, Ashish; Ellis, Christopher R; Milliren, Christopher; Hong, Jiarong; Scott, David; Arndt, Roger EA; Gulliver, John S;
Aerating hydroturbines have recently been proposed as an effective way to mitigate the problem of low dissolved oxygen in the discharge of hydroelectric power plants. The design of such a hydroturbine requires a precise understanding of the dependence of the generated bubble size distribution upon the operating conditions (viz. liquid velocity, air ventilation rate, hydrofoil configuration, etc.) and the consequent rise in dissolved oxygen in the downstream water. The purpose of the current research is to investigate the effect of location of air injection on the resulting bubble size distribution, thus leading to a quantitative analysis of aeration statistics and capabilities for two turbine blade hydrofoil designs. The two blade designs differed in their location of air injection. Extensive sets of experiments were conducted by varying the liquid velocity, aeration rate and the hydrofoil angle of attack, to characterize the resulting bubble size distribution. Using a shadow imaging technique to capture the bubble images in the wake and an in-house developed image analysis algorithm, it was found that the hydrofoil with leading edge ventilation produced smaller size bubbles as compared to the hydrofoil being ventilated at the trailing edge.
Gas entrainment behaviors in the formation and collapse of a ventilated supercavity, Experimental Thermal and Fluid Science, 2016, 79, 294
Gas transfer in a bubbly wake flow, IOP Conference Series: Earth and Environmental Science, 2016, 35, 012020
Karn, A., Ellis, C., Arndt, R., Hong, J., 2015, "Investigations into the turbulent bubbly wake of a ventilated hydrofoil: Moving toward improved turbine aeration techniques," Experimental Thermal and Fluid Science, Vol. 64, pp. 186-195.
Bohac, C. E. and Ruane, R.J., 1990, "Solving the dissolved oxygen problem," Hydro Review, Vol. 9, No. 1, pp. 62-73.
Thompson, E. J. and Gulliver, J. S., 1997, "Oxygen Transfer Similitude for Vented Hydroturbine," Journal of Hydraulic Engineering, Vol. 123, No. 6, pp. 528-538.
Ellis, C., Karn, A., Hong, J., Lee, S. J., Kawakami, E., Scott, D., Gulliver, J., Arndt, R. E. A., 2014, "Measurements in the wake of a ventilated hydrofoil: A step towards improved turbine aeration techniques," IOP Conference Series: Earth and Environmental Science, Vol. 22, pp. 062009.
Karn, A., Monson, G. M., Ellis, C., Hong, J., Arndt, R. E. A., Gulliver, J. S., 2015, "Mass transfer studies across ventilated hydrofoils: A step towards hydroturbine aeration," International Journal of Heat and Mass Transfer (In press).
Broder, D. and Sommerfeld, M., 2007, "Planar shadow image velocimetry for the analysis of the hydrodynamics in bubbly flows," Measurement Science and Technology, Vol. 18, No. 8, pp. 2513-28.
Karn, A., Ellis, C., Arndt, R., Hong, J., 2015, "An integrative image measurement technique for dense bubbly flows with a wide bubble size distribution," Chemical Engineering Science, Vol. 122, pp. 240-249.
Meyer, F., 1994, "Topographic distance and watershed lines," Signal Processing, Vol. 38, No. 1, pp.113-125.