共查询到20条相似文献,搜索用时 343 毫秒
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利用智能手机自制简易实验装置,搭建了一套驻波法声速测量系统,实现了声波在空气和不同液体介质中的传播速度的准确测量。实验使用手机FreqCounter APP产生单频声波信号,采用DaTuner APP软件检测实时频率和声音强度,通过测得相邻波腹或波节间的距离,根据其与频率和声速间的关系即可求出所测声速值。所取得实验结果与理论值具有良好的一致性。 相似文献
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为了研究气固两相流动大涡模拟中合适的曳力计算模型,本文引入拟颗粒和拟颗粒表面能的概念,通过拟颗粒表面能与外界输入能量之间的平衡关系来确定拟颗粒的粒径。根据拟颗粒粒径,得到运算量较小且考虑颗粒团聚效应的曳力计算模型。应用本文的曳力计算模型对二维竖直槽道内稠密气固两相流动进行了大涡模拟,结果表明颗粒的浓度分布具有上稀下浓,壁面附近浓中心稀及颗粒聚集等特点。这与实验结果在定性上是一致的。对气相和颗粒相的瞬时速度场进行了分析,发现气相和颗粒相速度场分布的非对称性是形成颗粒浓度分布壁面附近浓中心稀的重要原因之一。 相似文献
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超细颗粒悬浊液中声衰减和声速的数值分析研究 总被引:13,自引:1,他引:12
为研究应用超声测量超细颗粒的粒度和浓度,本文由描述声波在悬浊液中传播的Allegra &Hawley数学模型出发,通过两个算例的数值模拟计算,研究了二氧化钛-水,铁粉-水两种超细颗粒悬浊液中声波传播的衰减和相速度,分析了声波的频率、颗粒尺寸和浓度对衰减和相速度的影响规律,并讨论了计算模型对不同物性参数的敏感程度。 相似文献
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Knobles DP Koch RA Thompson LA Focke KC Eisman PE 《The Journal of the Acoustical Society of America》2003,113(1):205-222
Part of an experiment to test a measurement package in a shallow water region in the Gulf of Mexico was designed to gather broadband acoustic data suitable for inversion to estimate seabed geoacoustic parameters. Continuous wave tow acoustic signals at multiple frequencies and broadband impulsive source signals were recorded on a horizontal line array in a high-noise environment. Simulated annealing with a normal mode forward propagation model is utilized to invert for a geoacoustic representation of the seabed. Several inversions are made from different data samples of two light bulb implosions, the measured sound speed profiles at the HLA and at the positions of the light bulb deployments, and for two different cost functions. The different cost functions, measured sound speed profiles, and measured time series result in different inverted geoacoustic profiles from which transmission loss is generated for comparison with measurements. On the basis of physical consistency and from the comparison of the transmission loss and time series, a best estimate geoacoustic profile is selected and compared to those obtained from previously reported inversions. Uncertainties in the sound speed profile are shown to affect the uncertainties of the estimated seabed parameters. 相似文献
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Using a multi-layered transducer model to estimate the properties of paraffin wax deposited on steel
When using ultrasound for detecting low impedance materials on the surface of high impedance materials, a major challenge is the contrast difference between the strong reverberations from the high impedance material and the weak echoes received from the low impedance material. The purpose of this work is to present the theoretical and experimental validation of an ultrasonic methodology for estimating the acoustical properties of paraffin wax on the surface of steel. The method is based on modeling and inversion of the complete electro-acoustic channel from the transmitted voltage over the active piezoelectric element, to the received voltage resulting from the acoustic reverberations in the multilayered structure. In the current work, two conceptually different models of the same multi-layer transducer structure attached to steel is developed and compared with measurements. A method is then suggested for suppressing the strong reverberations in steel, hence isolating the wax signals. This contrast enhancement method is fitted to the model of the structure, facilitating parameter inversion from the wax layer. The results show that the models agree well with measurements and that up to three parameters (travel time, impedance and attenuation) can be inverted from the wax simultaneously. Hence, given one of the three parameters, density, sound speed or thickness, the other two can be estimated in addition to the attenuation. 相似文献
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为探讨混凝土箱梁噪声的时变特性,以京沪高铁32 m混凝土简支箱梁为原型,制作了1:10的缩尺模型,通过模态试验的方法验证箱梁模型与原型的相似关系,通过声学试验验证箱梁声学计算模型的正确性。然后,建立了箱梁缩尺模型与原型两种计算模型,利用有限元和边界元法求出两种模型的瞬态结构噪声。研究发现,箱梁缩尺模型与箱梁原型的材料参数满足一定关系,模型试验的方法能够验证箱梁模型与箱梁原型之间符合相似关系,箱梁模型的振动噪声测试结果能真实反映原型振动噪声水平。两种模型的结构噪声在时域内声压级及对应场点的声压存在一定相似关系。该研究可为箱梁缩尺模型结构噪声反演至箱梁原型提供依据,所采用的方法和得到的结果对桥梁结构振动与声辐射实验研究具有参考作用。 相似文献
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超声吸收体的物理参数对利用水听器和红外热成像技术的高强度聚焦超声(High-Intensity Focused Ultrasound,HIFU)声场测量结果具有重要影响。为了探索超声吸收体的物理参数(密度、声速、衰减系数、热扩散系数、定压比热容)对测量结果的影响规律,本文根据层状模型计算出相同声源功率输出时不同物理参数对应的超声吸收体内部声场和热场,利用有限差分法计算出超声吸收体表面在辐照过程中的温度变化;利用基于水听器和红外热成像技术的聚焦声场测量方法测量出焦域内不同位置上声场特征值(轴线声强和-6 dB声束宽度),与通过理论计算得到的声源在纯水中声场特征值进行比较,分析了不同物理参数对测量结果的影响。超声吸收体的声、热学参数中除了声速外,其它物理参数的变化引起声场特征值的测量造成最大相对差异率小于15%。因为声波传播速度的改变会导致超声吸收体内部热场分布变化,使测量结果与理论计算值有较大偏差,其中-6 dB声束宽度和轴线声强最大相对差异率为95.37%和69.97%。因此在选择超声吸收体的声、热学参数时应重点关注声波在吸收体内声速的影响。超声吸收体的声学参数与水的声学参数相近时,可以在焦域内获得较好的测量结果。 相似文献
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在假定钻铤是光滑的提前下,前人理论模拟了随钻测井的声压波形,但未发表关于理论波形与实验波形的比较的文章。为了认识测量信号所对应的力学类型及相应类型的钻铤波在钻铤内的分布,本文将理论模拟的随钻声波测井波形与实验波形进行对比。与前人单独考虑压电效应或井孔传播效应不同,本文模拟单极随钻声波测井响应时,将发射器、接收器、光滑钻铤和井孔结构作为一个整体,采用有限元法计算模拟了电压源激励下接收器纪录的声压信号和位移信号。将模拟的声压波形与电压信号进行比较,发现二者的钻铤波与斯通利波相对幅值相差较大,而模拟的径向位移波形更接近电压信号。进一步比较理论波形与小模型井内实验测量到的电压信号,证实电压信号更接近位移信号而与声压信号差异明显。这表明当钻铤光滑时,单极随钻声波测井换能器感知的主要是径向位移信号。研究还表明声压信号中的钻铤波能量主要集中在钻铤内壁,径向位移信号中的钻铤波能量主要集中在钻铤外壁。 相似文献
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讨论了一种适用于浅海的时变声速剖面跟踪方法。该方法将时变水体声速剖面的反演问题建模为由描述声速剖面时变特性的状态方程与包含声压场局部测量信息的测量方程组成的状态-空间模型,提出利用自回归分析拟合方法将声速场扰动建模为高阶自回归演化模型,并通过集合卡尔曼滤波序贯地估计时间演化的海洋声速场。利用2001年亚洲海实验环境与声速测量数据,仿真分析了基于高阶自回归演化模型的时变声速剖面集合卡尔曼滤波估计方法。结果表明,相比于利用传统随机游走状态演化模型的估计方法,该改进方法可有效降低声速的跟踪误差,并且在较低信噪比条件下仍具有较好的跟踪性能。 相似文献
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J. Ducourneau 《Applied Acoustics》2003,64(9):845-862
This study concerns the determination of an equivalent acoustic absorption model of the flat heterogeneous walls present in industrial rooms. Numerous measurements of the reverberation time in reverberant room were carried out for several facings with different distributed spatial absorption. Experimental results were compared to classical reverberation time models. The measurements showed that the change in average acoustic absorption depends on the relative distance between the sound source and the absorbent panels, as it is this which creates heterogeneity. Therefore, taking into consideration, in the theoretical models of average acoustic absorption studied, the solid angles representing the equivalent area of the panels as viewed by the source, improved the accuracy of the calculated reverberation time compared to the measurements. This equivalent acoustic absorption model, based on Sabine's absorption coefficient and employing the solid angle ratio, was used to calculate the reverberation time of several industrial rooms. The results obtained are better than those obtained with the standard formula. 相似文献
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A novel method for the measurement of acoustic speed 总被引:1,自引:0,他引:1
Traditional methods for measuring acoustic speed require knowledge of either the specimen thickness or the distances between the transducers and the specimen. In general, the accuracy in measuring these quantities determines the accuracy of the experimental technique for measuring speed. This problem is particularly acute in measuring sound speed in biological specimens. A new method for measuring acoustic speed of materials, which eliminates the need for determining these quantities, has been developed. The technique, which necessitates the use of only one transducer, requires measurement of four times of flight of a sound pulse and the knowledge of the speed of sound in a reference fluid medium in which the specimen is placed. Ultrasonic speed in stainless steel and Plexiglas was measured using this method to verify its validity. Results on measurements on porcine liver, myocardium, and soft fat are also reported. 相似文献