Zegao Yin

Theoretical analysis and experimental study of oxygen transfer under regular and non-breaking waves

The dissolved oxygen concentration is an important index of water quality, and the atmosphere is one of the important sources of the dissolved oxygen. In this paper, the mass conservation law and the dimensional analysis method are employed to study the oxygen transfer under regular and non-breaking waves, and a unified oxygen transfer coefficient equation is obtained with consideration of the effect of kinetic energy and wave period. An oxygen transfer experiment for the intermediate depth water wave is performed to measure the wave parameters and the dissolved oxygen concentration. The experimental data and the least squares method are used to determine the constant in the oxygen transfer coefficient equation. The experimental data and the previous reported data are also used to further validate the oxygen transfer coefficient, and the agreement is satisfactory. The unified equation shows that the oxygen transfer coefficient increases with the increase of a parameter coupled with the wave height and the wave length, but it decreases with the increase of the wave period, which has a much greater influence on the oxygen transfer coefficient than the coupled parameter.

Oxygen Transfer by Air Injection in Horizontal Pipe Flow

AbstractDissolved oxygen (DO) concentration is an important water quality parameter. This paper studies the increase of DO concentration in water by air injection into a horizontal pipe flow. A 3D computational fluid dynamics model was employed to compute the water and bubble mixture flow with a DO transport model. Experiments were also conducted to validate the mathematical model. A relative saturation coefficient relationship was developed with air bubble volume fraction and travel time. An oxygen absorption efficiency is defined, and its relationship with the inlet DO concentration, air bubble volume fraction, and travel time was discussed.

Initial Velocity Effect on Acceleration Fall of a Spherical Particle through Still Fluid

A spherical particle’s acceleration fall through still fluid was investigated analytically and experimentally using the Basset-Boussinesq-Oseen equation. The relationship between drag coefficient and Reynolds number was studied, and various parameters in the drag coefficient equation were obtained with respect to the small, medium, and large Reynolds number zones. Next, some equations were used to derive the finite fall time and distance equations in terms of certain assumptions. A simple experiment was conducted to measure the fall time and distance for a spherical particle falling through still water. Sets of experimental data were used to validate the relationship between fall velocity, time, and distance. Finally, the initial velocity effect on the total fall time and distance was discussed with different terminal Reynolds numbers, and it was determined that the initial velocity plays a more important role in the falling motion for small terminal Reynolds numbers than for large terminal Reynolds number scenarios.

Numerical Study on the Effects of Submerged Breakwater on Wave Overtopping

ABSTRACT Wang, Z.; Yin, Z.; Chen, Y., and Yang, B., 2017. Numerical study on the effects of submerged breakwater on wave overtopping. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 264–248. Coconut Creek (Florida), ISSN 0749-0208. In order to protect beach or mud coastlines, submerged breakwaters are built in the world widely. When the submerged breakwater is designed, one important issue having to be analyzed is wave overtopping of coastlines or coastal preventing structures since the wave overtopping is very dangerous for people or structures on the potential coastal zones with probability of wave overtopping appearing. A 2-D numerical wave flume has been established based on Flow-3D software to investigate effects of incident wave parameters in front of the submerged breakwaters, slope of the beach and the submerged breakwaters themselves, respectively. The numerical wave flume has been verified by the theoretical data of wave equation and wave frequency spectrum of physical experiment. The computational results fitted well with the theoretical data. The calculated values of the overtopping are in good agreement with the physical model test values under the conditions of random wave. The verified model has been used to calculate the wave overtopping under the different wave height, wave period and slope of the beach. The results of numerical model test indicate that the wave overtopping without a submerged breakwater is much more than that with one for random wave approaching, which is similar as phenomena found in physical experiments. The relationship between wave overtopping and wave height, wave period, slope of the beach was discussed. And a new empirical formula to calculate the overtopping was fitted based on the method of dimensional analysis.

Experimental study of dissolved oxygen transport by regular waves through a perforated breakwater

The perforated breakwater is an environmentally friendly coastal structure, and dissolved oxygen concentration levels are an important index to denote water quality. In this paper, oxygen transport experiments with regular waves through a vertical perforated breakwater were conducted. The oxygen scavenger method was used to reduce the dissolved oxygen concentration of inner water body with the chemicals Na2SO3 and CoCl2. The dissolved oxygen concentration and wave parameters of 36 experimental scenarios were measured with different perforated arrangements and wave conditions. It was found that the oxygen transfer coefficient through wave surface, K1a1, is much lower than the oxygen transport coefficient through the perforated breakwater, K2a2. If the effect of K1a1 is not considered, the dissolved oxygen concentration computation for inner water body will not be greatly affected. Considering the effect of a permeable area ratio a, relative location parameter of perforations δ and wave period T, the aforementioned data of 30 experimental scenarios, the dimensional analysis and the least squares method were used to derive an equation of K2a2 (K2a2=0.0042a0.5δ0.2T-1). It was validated with 6 other experimental scenarios data, which indicates an approximate agreement. Therefore, this equation can be used to compute the DO concentration caused by the water transport through perforated breakwater.

Oxygen Transfer Numerical Investigation Using Intermittent Aeration Technology Under Regular Waves

Based on a combination of Reynolds-Averaged Navier-Stokes equations, standard k-ε equations, and VOF technique, a 2-D dissolved oxygen transport mathematical model was conducted to investigate oxygen-supply characteristics for regular waves with a given still water depth d and various hydrodynamic parameters (incident wave height H and wave period T equivalent to incident wave length L) and intermittent aeration parameters (air flow rate per unit width q, aeration period Ta, aeration depth da and air source area Aa). A series of experiments were conducted to validate the mathematical model, and they agreed well with each other. In addition, a series of dimensionless parameters were conducted to assess their relationships with oxygen transfer coefficient respectively. It was found that oxygen transfer coefficient increased slightly with the increase of q/g2Ta3

Experimental Wave Attenuation Study over Flexible Plants on a Submerged Slope

q/{g}^2{T}_a^3

Numerical Investigation of Wave Reflection from a Stepped Breakwater

. With the increasing da2/Aa