Single Beam Water Discharge Into The Water Process And Its Water Noise Experimental Study

When water flows down into the water,it produces sound.A large amount of water on the dam(weir)flows down and collides with the downstream water at the incident point,adding a large amount of gas to escalate the sound into water noise.This water noise pollution has seriously affected the production and life of nearby residents.The hydraulic characteristics of the discharge water on different sections of rubber dams and overflow weirs vary,and can be approximated as a continuous flow(curtain)formed by coupling several single streams of water.Due to the same physical process and water noise generation mechanism of air entrainment in the discharged water of the two,research on the air entrainment phenomenon and water noise in the discharged water of water conservancy facilities can start from a single beam of water flow,compare and analyze the impact of air entrainment process in a single beam of water flow and the air entrainment process in the receiving water body on the characteristics of water noise,and clarify the sound generation mechanism of water noise in a single beam of water flow,Then,the mechanism of water noise generation in hydraulic engineering is determined through the coupling relationship of noise.This article uses physical model testing methods to study the noise problem of a single beam of water falling into a circular hole.High speed camera technology is used to collect images of the process of a single beam of water falling into the water under different working conditions.Photoshop and CAD software are used to post-process the images and label the feature dimensions.Based on different experimental results,qualitative description and quantitative analysis are conducted on the characteristics of the single beam of water falling into the air and the characteristics of water aeration,Using the Zonicbook/618 noise and vibration analyzer and AWA8228+handheld sound level meter to collect time-domain and frequency-domain signals under various operating conditions,and filtering the background noise,a method for analyzing the correspondence between water inflow images and water noise is proposed to determine the mechanism of single beam water inflow noise generation.Then,based on the differences in water noise generation mechanisms,it is classified and the characteristics of different types of water noise are analyzed using spectral analysis,The final relationship between the sound pressure level value L_pof the effluent noise and the relative aeration concentration C.The main conclusions of the study are as follows:(1)In the single-beam water flow aerial formThe continuous length of a single stream is positively correlated with the outlet flow velocity,while at the same flow rate,the continuous length is negatively correlated with the nozzle aperture;The Weber number We and the dimensionless continuous length L_c/d form a quadratic function function relationship,and the decreasing rate gradually slows down.A single stream of water breaks into main droplets and satellite droplets in the air.The diameter of the main droplet is of the same order as the inner diameter of the nozzle,and the diameter of the main droplet is about 6-8 times that of the satellite droplet;Breaking water droplets undergoes periodic vibration,and the vibration period increases with the increase of water droplet particle size,but the particle size does not change its vibration form;The different polymerization methods between water droplets will affect the aeration process and the water entry process,with the polymerization method of the front and rear main water droplets having the greatest impact,while the flow rate will affect the probability of polymerization between broken water droplets.(2)In the single bundle of water into the water processWhen a single beam of water enters the water in the form of a dense water column,the amount of air entrainment near the incident point is very small and the form of air entrainment is single.When entering the water in the form of broken water droplets,the receiving water body will form a dense bubble area,and the bubbles will undergo the process of sinking,breaking,floating,merging,exiting,oscillating,fracturing,and collapsing into the water surface.The amount of air entrainment is large and the forms of air entrainment are diverse;During the period when the receiving water body is in a stable turbulent state,the relative aeration concentration is positively correlated with the falling height,and the growth rate is increasing.Compared with the process of a single water droplet entering the water,the aeration of the front water droplet in the air is limited and is subject to consistent changes in the morphology of the receiving water body;Divide water wings into small water wings,crown water wings,broken water wings,and closed water wings;The momentum per unit area is related to the dimensionless height H_bof the water wing in a cubic polynomial,and the growth rate of H_bshows a trend of first increasing and then decreasing.(3)In the single bundle of water inflow water noiseThe mechanism of single beam water flow noise generation can be divided into:water water turbulence noise,water air turbulence noise,and bubble rupture noise.The main frequency range of water water turbulence noise is 500-630Hz,which belongs to intermediate frequency noise and has extremely low intensity.The main frequency range of water air turbulence noise is 4000-6300Hz,which belongs to high-frequency noise and has high intensity.The main frequency range of bubble rupture noise is 10000-16000Hz,which belongs to high-frequency noise,And the sound wave intensity generated by the rupture of a single bubble is relatively low;The sound pressure level value L_pof water noise has a power function relationship with the relative air concentration C,and the growth slope of the sound pressure level value gradually slows down.The noise caused by water droplets entering aquatic products in the front end is accompanied by the generation of water wings.The ventilation zone walls formed by water wings and cavities reflect,refract,and absorb sound waves,resulting in significant energy loss of sound waves;During the process of water droplets entering the front and reaching the maximum height of the water wing,the main frequency range of water air turbulence noise is10000-16000Hz,which belongs to high-frequency noise and has high intensity;The momentum per unit area of water droplets shows a fifth degree polynomial correlation with the maximum sound pressure value,and the slope of sound pressure value growth gradually slows down.