有限差分法模拟单位冲激函数声波在钻柱中传播

为实现声波为载波,钻柱为信道传输井下信息的目的,了解声波在钻柱中的传输规律是必要的. 将钻柱简化为理想周期性管结构,利用有限差分方法,对单位冲激函数声信号在钻柱中传播进行了模拟,分析接收信号时域及频域分布得出：响应信号持续时间较长,信号随时间增长衰减,且最大幅值较输入信号小；钻柱结构的信道为梳状滤波器结构；通带存在谐振尖峰,尖峰数量与钻杆及接头数量有关. 模拟结果与同类研究成果有较好的一致性.

NUMERICAL SIMULATION OF THE UNIT IMPULSE FUNCTION ACOUSTIC SIGNAL PROPAGATION IN DRILL STRING STRUCTURE USING FINITE DIFFERENCE METHOD

In order to realize transmission underground information,using acoustic as the carrier and using the drill string as the transmission channel,it is necessary to understand the transmission characteristics of different types acoustic wave transmited in drill string.The drill string is simplified as ideal periodic tube structure.Finite-difference method is employed to simulate and analyse the unit impulse function acoustic signal propagation in periodic tube structure.Based on the obtained time domain and frequency domain distribution of the signals,the following conclusions are given.The output end will receive a relatively long time signal under the excitation of the unit impulse function acoustic signal,the signal will decay with the increase of time,and maximum amplitude is less than the input signal;drill string channel structure is the comb filter structure;pass band exists resonant peak,peak number is associated with the number of drill pipe and joints.The simulation results have good consistency with similar research results and verify that the feasibility and validity of the mathematical model and numerical method adopted.