Research On The Characteristics Of Water Entry Noise Of Low-speed Objects

Object water-entry noise is the transient noise signal formed under the water surface of the impact point when the object penetrates the water from the air into the water medium.Different noise signals reflect the characteristics of different water objects.Rainfall noise in nature also belongs to the noise of water entering the object,and the noise characteristics of a single raindrop reflect the characteristics of the noise of the rain.At present,there is less research on the energy of the noise of the water entering the object.Therefore,this paper chooses two more typical fluids: single raindrop and solid steel ball.And rigid body,the acoustic characteristics of transient noise generated by the two entering the water are studied.In order to ensure the reliability of the experimental results,two devices are designed for launching the steel ball and generating a single raindrop,which can ensure that the steel ball and raindrop fall vertically into the water without rotation.Under the condition that other conditions remain the same,by changing the particle size of a single raindrop,the particle size of a steel ball,and the falling height,the transient sound of the water inflow of the steel ball and the raindrop into the water at a low speed is measured separately,and the characteristics of the sound of the water inflow between the two are analyzed.,Analyze the sound pressure amplitude and frequency range of the initial impact sound and bubble pulsation sound of the steel ball and single raindrop,and explain the frequency range of the bubble pulsation sound of the two shrinks with time.The impact sound and bubble pulsation are explained.Acoustic energy and acoustic energy conversion efficiency are calculated.In order to explore the general law of the sound of water entering the object,the characteristics of the sound of the steel ball entering the water and the sound of the rain falling into the water are compared,and the similarities and differences between the two are summarized.In addition,the "silence of the noise of the steel ball entering the water" "Area" disturbance signal was analyzed,and its frequency was inversely proportional to the particle size of the steel ball.It was inferred that the cause was the pulsating radiation of large bubbles generated when the steel ball entered the water.The research results show that: light raindrops and medium raindrops do not generate acoustic signals,small raindrops do not produce impact sounds,100% of the first type ofbubbles are generated,and large raindrops and extreme raindrops produce impact sounds each time they hit the water surface,and probabilistically The energy of the second and third types of bubble pulsations is roughly equivalent to the impact sound.These measurements are consistent with the experimental measurements in the classic literature;each time the steel ball impacts the water surface,it produces an impact sound and bubble pulsation sound,and the energy of the bubble sound is much greater than the impact Sound energy.The acoustic energy conversion efficiency of steel balls is slightly higher than that of raindrops with similar volume.When the particle size is constant,the frequency range of bubble pulsation sound of steel balls and raindrops decreases with time.This paper also studies the relationship between kinetic energy and acoustic energy when the steel ball enters water,and finds that under the experimental conditions of this article,the kinetic energy and acoustic energy of the steel ball when it enters water is approximately linear.