The improved separation method of coherent sources with two measurement surfaces based on statistically optimized near-field acoustical holography

A technique for separating coherent sources measured by two parallel arrays is proposed. The two measurement surfaces located in the opposite directions of the coherent sources. Similar to separate the aim source from background noise, this method can separate the single source from coherent sources, which makes the sound field information of single source in complex environment more accurate. Such improved separation method based on statistically optimized near-field acoustical holography, according to the sound pressure relationship between measurement surfaces and reconstruction surfaces to separate the sources, reduces the measurement data and obtains higher precision of reconstruction. The present paper uses the improved separation method to obtain the single source results from numerical simulations, gives the relative reconstruction errors with frequency from 100 Hz to 1400 Hz, and practical measurement

Gas-Liquid Stratified Flow in Pipeline with Phase Change

When the natural gas with vapor is flowing in production pipeline, condensation occurs and leads to serious problems such as condensed liquid accumulation, pressure and flow rate fluctuations, and pipeline blockage. This chapter aims at studying phase change of vapor and liquid-level change during the condensing process of water-bearing natural gas characterized by coupled hydrothermal transition and phase change process. A hydrothermal mass transfer coupling model is established. The bipolar coordinate system is utilized to obtain a rectangular calculation domain. An adaptive meshing method is developed to automatically refine the grid near the gas-liquid interface. During phase change process, the temperature drop along the pipe leads to the reduction of gas mass flow rate and the rise of liquid level, which results in further pressure drop. Latent heat is released during the vapor condensing process which slows down the temperature drop. Larger temperature drop results in bigger liquid holdup while larger pressure drop causes smaller liquid holdup. The value of velocity with phase change is smaller than that without phase change while the temperature with phase change is bigger. The highest temperature locates in gas phase. But near the pipe wall the temperature of liquid region is higher than gas region

The source localization technique based on improved functional beamforming using a virtual array

Beamforming have become a popular technique to identify sound source. The most common application is conventional beamforming, but it has low resolution and requires a large number of microphones at low frequency. To overcome this problem, an improved functional beamforming method based on “virtual array” and the relative spectral matrix is introduced. Firstly, the relative complex pressures of the sound field can be acquired by “virtual array” with one scanning microphone and a fixed reference microphone. Thereby, a relative spectral matrix of the relative complex pressures measured can be obtained. Then the improved functional beamforming method with order v is developed based on the relative spectral matrix. And the resolution of the improved method can be modified by increased the number of order v. but it also can be improved by changing virtual microphones. This property allows widening the scope of this interesting beamforming method