切向流作用下直通穿孔管阻性消声器传递损失预测

Prediction of transfer loss in a straight-through perforated pipedissipative muffler under tangential flow

使用考虑涡黏系数的频域线性纳维斯托克斯方程(linearized Navier-Stokes equations, LNSEs)计算切向流作用下直通穿孔管阻性消声器的传递损失,计算步骤为:运用CFD(computational fluid dynamics)方法求解计算域内的时间平均流动变量,然后将变量映射至声学网格;将声传播介质分为空气和吸声材料,后者等效为具有复声速和复密度的流体,使用频域LNSEs计算声场,最后利用平面波分解法计算消声器的传递损失。计算结果与试验测量结果吻合良好,从而证明了计算方法的正确性。通过数值计算分析了切向流马赫数对不同流阻率和穿孔结构阻性消声器传递损失的影响规律。随着切向流马赫数的增加,消声器在低频域的传递损失有所降低,中高频消声性能变化无明显规律可循;切向流对低穿孔率消声器传递损失的影响大于高穿孔率。

Here,the frequency-domain linearized Navier-Stokes equations(LNSEs)considering eddy viscosity coefficient was used to calculate transfer loss of a straight-through perforated pipe dissipative muffler under tangential flow.Calculation steps were as follows:(1)CFD(computational fluid dynamics)method was used to solve time-averaged flow variables in calculation domain,and then theses variables were mapped to acoustic grid;(2)acoustic propagation medium was divided into air and sound-absorbing material,the latter was equivalent to a fluid with complex sound velocity and complex density,the frequency-domain LNSEs was used to calculate sound field,at last the plane wave decomposition method was used to calculate and predict the transfer loss of the muffler.The calculation results agreed well with the experimental measurement results to verify the correctness of the calculation method.Influence laws of tangential flow Mach number on transfer losses of dissipative mufflers with different flow resistance rates and perforated structures were analyzed with numerical calculation.The results showed that with increase in tangential flow Mach number,the transfer loss of the muffler within low frequency-domain decreases,but there is no obvious law for the change of the muffler performance at mid and high frequencies to follow;effects of tangential flow on transfer losses of mufflers with low perforation rate are larger than those with high perforation rate.