ass日本风韵熟妇pics男人扒开女人屁屁桶到爽|扒开胸露出奶头亲吻视频|邻居少妇的诱惑|人人妻在线播放|日日摸夜夜摸狠狠摸婷婷|制服 丝袜 人妻|激情熟妇中文字幕|看黄色欧美特一级|日本av人妻系列|高潮对白av,丰满岳妇乱熟妇之荡,日本丰满熟妇乱又伦,日韩欧美一区二区三区在线

In order to research the internal sound field characteristics and reduce the running noise of vertical pipeline pump, the CFD and Lighthill sound analogy theory was adopted to solve the internal flow and acoustic field. The sawtooth structure of the owl feather was used to conduct bionic optimization to reduce noise. Firstly, the pressure fluctuation of pipeline pump at 0.8Qd, Qd and 1.2Qd were obtained from the unsteady simulation with the RNG k-ε turbulence model in CFX software. The datum of pressure fluctuation were extracted and input into the LMS Virtual.lab acoustics software, the SPL of the pump discharge, internal sound pressure distribution and main noise source in pumps at different flows were got by acoustic field calculation. The simulation results showed that the flowinduced noise of pipeline pump was closely related to the pressure fluctuation which was mainly caused by rotorstator interaction，both of them had the same frequency characteristic, the sound pressure was mainly distributed in shaft frequency, blade frequency and frequency multiplication, the maximum sound pressure appeared at 1 time blade passing frequency. With the decrease of the flow rate, the SPL of the pump discharge was increased. Then, based on the bionics principle, the similarity criterion was used to establish the bionic blade model with reference to the structure characteristics of the specimen of the owl wings. Three parameters, including tooth width, tooth pitch and tooth width were constructed to control the geometry of the bionic blade,，and these parameters were chosen to design 16 orthogonal test models. Finally, the internal flow and sound field datum of different impellers under different working conditions were got by calculation. Compared with the optimal model,，the result showed that the bionic blade with sawtooth structures can reduce the pressure fluctuation, stabilize the flow field and reduce the noise. Noise reduction was obvious under the design condition, and the noise of the blade frequency was decreased as high as 8dB.