Research On Characteristics Of Bubbles In Aerated Open-Channel-Flow & Image Analysis Method

A large number of huge hydroelectric projects have to be built to produce energy to meet the demand of the high speed development of national economy. And aeration problem largely exists in those huge hydraulic projects and demand a thorough solution.In this paper, the author used a new type of air concentration and viscosity probe instrument, and measured the velocity, air concentration and bubble size distribution, and obtained some important conclusions as below:During the development of aeration along the flow direction, there exist a height at which the air concentration is a constant, which equals 40%; in partial aerated flow area velocity distribution are similar on the first section and the difference between aerator and self-aeration is increase as the flow go downstream, and aerator makes velocity bigger than self-aerated flow; after non-dimension process, the velocity distribution shows high similarity.As the same section is concerned, near the bottom the maximum value of frequency appear within 1mm of bubble size, towards the water face this value tend to decrease, yet the corresponding size turns to increase; in the same time, the frequency is concentrated near the bottom and deconcentrated near the water face; under the experiment condition, the maximum frequency of the total section approximately appear at 0.5mm size; mean bubble size access 0 at bottom and increase acceleratively towards water face where tend to be infinite; total number increase during developing of aeration, and become steady when reach wholly developed area; on the same section, the total number in unit time tend to increase at first and decrease then, along the water depth.At the same time, this paper studied the application of image analysis method in the analysis of bubble characteristics. Improved the Ostu's method, developed a man-machine system to partial separate and make-whole, and a mass-document dealing system. Introduced the before-treatment and after-treatment system to refine the separation of image and obtain the relevant statistic value, gained the whole information of air concentration and size, shape and volume of every bubbles; collaborated with the velocity of bubbles get airintake.