TY - JOUR JF - mdrsjrns JO - Modares Mechanical Engineering VL - 17 IS - 1 PY - 2017 Y1 - 2017/3/01 TI - Experimental investigation of surface pressure spectra beneath turbulent boundary layer over a flat plate with microphone TT - بررسی تجربی طیف فشار سطح لایه مرزی آشفته روی صفحه تخت با استفاده از میکروفون N2 - Surface pressure fluctuations beneath turbulent boundary layer on a flat plate have complex physical behavior and due to its importance in acoustic noise generation, extensive studies have been devoted to predicting or measuring the surface pressure behavior. In the present study to investigate the surface pressure fluctuations under zero pressure gradient, a flat plate with a chord length of 580 mm has been used. All experiments were carried out in a subsonic wind tunnel and at three free-stream velocities: 10, 15 and 20 m/s. In order to measure unsteady pressure fluctuations, a condenser microphone is used as a pressure transducer. Moreover, various parameters of turbulent boundary layer are measured to provide the input variables of semi-empirical models. A single constant temperature hot-wire anemometer has been used for boundary layer measurement. Surface pressure spectra has been measured at various velocities and their collapse on a single curve by normalizing with different variables of turbulence boundary layer is studied. The results show that the best collapses in low and middle frequencies can be obtained by using mixed variables. However, in high frequency range the pressure spectra collapses when it is normalized by inner layer scales. Finally, after ensuring the accuracy of surface pressure spectra results, the efficiency of semi-empirical models for predicting turbulent boundary layer wall pressure spectra is evaluated. The results show the effectiveness of the Goody’s semi-empirical model for prediction of surface pressure spectra by using turbulent boundary layer parameters. SP - 263 EP - 272 AU - Afshari, Abbas AU - Dehghan, Aliakbar AU - Kalantar, Vali AU - Farmani, Mohammad AD - KW - Surface pressure fluctuations KW - Turbulent boundary layer KW - Pressure spectra KW - Semi-Empirical models UR - http://mme.modares.ac.ir/article-15-8508-en.html ER -