The sound generated by a NACA0012 airfoil in the wake of a rod is numerically simulated by two approaches, one is the large eddy simulation （LES） with the FW-H acoustic analogy and the other is the LES with the Powe...The sound generated by a NACA0012 airfoil in the wake of a rod is numerically simulated by two approaches, one is the large eddy simulation （LES） with the FW-H acoustic analogy and the other is the LES with the Powell vortex sound theory, in order to compare the accuracies of their predictions. The vortical structures around the rod-airfoil are computed by the LES and captured by the vortex identification （Q）. The acoustic predictions are verified by the measurements. It is shown that the computed results by the two hybrid approa- ches （LES and FW-H, LES and Powell） are very similar. Both are shown to be satisfactory in the prediction of the noise generated by an unsteady flow. Subsequently, the numerical simulations of the wall pressure fluctuations and the flow-induced noise of a NACA0015 airfoil are made by the two hybrid approaches. At two angles of attack （ 0~ and 8~ ）, the wall pressure fluctuations of the NACA0015 airfoil are computed. The obtained power spectra of the wall pressure fluctuations are analyzed and compared with the measured data. And the vortical structures around the airfoil at two angles of attack are simulated and analyzed. After that, the flow induced noises of the NACA0015 airfoil at two angles of attack are predicted by the two hybrid approaches （LES and FW-H, LES and Powell）. The radiated sound spectra are analyzed and compared with the experimental data. Comparisons show that both are robust, credible and satisfactory in the numerical prediction of the flow induced noise. All numerical simulations are carried out by parallel processing in the Wuxi supercomputing center.展开更多
Centrifugal pumps are widely used in engineering for a variety of applications.A known drawback of these devices is the high-level noise generated during operations,which can affect their stability and adversely influ...Centrifugal pumps are widely used in engineering for a variety of applications.A known drawback of these devices is the high-level noise generated during operations,which can affect their stability and adversely influence the entire working environment.By combining the Powell vortex sound theory,numerical simulations and experimental measurements,this research explores the trends of variation and the corresponding underlying mechanisms for the flow-induced noise at various locations and under different operating conditions.It is shown that the total sound source intensity(TSSI)and total sound pressure level(TSPL)in the impeller,in the region between the inlet to the outlet and along the circumferential extension of the volute,are much higher than those at pump inlet and outlet.Additionally,under various rotational speeds with the design flow rate(Condition 1),the TSSI and TSPL at pump inlet and outlet are higher than those obtained with the opening of the valve kept unchanged(Condition 2);vice versa when these two parameters are evaluated at various locations in the impeller and the volute under the Condition 2,they exceed the equivalent values obtained for the other Condition 1.展开更多
In this paper, the measurement of an aerodynamic sound source for a semi-circular cylinder in a uniform flow is described using Particle Image Velocimetry (PIV). This experimental technique is based on vortex sound th...In this paper, the measurement of an aerodynamic sound source for a semi-circular cylinder in a uniform flow is described using Particle Image Velocimetry (PIV). This experimental technique is based on vortex sound theory, where the time derivative of vorticity is evaluated with the aid of two sets of standard PIV systems. The experimental results indicate that the sound source for the semi-circular cylinder is located around the shear layer near the edge of the semi-circular cylinder. The sound source intensity and the area are reduced in the semi-circular cylinder compared with those of a circular cylinder. This result indicates that the aerodynamic sound of the semi- circular cylinder is smaller than that of the circular cylinder, which supports the microphone measurement result.展开更多
文摘The sound generated by a NACA0012 airfoil in the wake of a rod is numerically simulated by two approaches, one is the large eddy simulation （LES） with the FW-H acoustic analogy and the other is the LES with the Powell vortex sound theory, in order to compare the accuracies of their predictions. The vortical structures around the rod-airfoil are computed by the LES and captured by the vortex identification （Q）. The acoustic predictions are verified by the measurements. It is shown that the computed results by the two hybrid approa- ches （LES and FW-H, LES and Powell） are very similar. Both are shown to be satisfactory in the prediction of the noise generated by an unsteady flow. Subsequently, the numerical simulations of the wall pressure fluctuations and the flow-induced noise of a NACA0015 airfoil are made by the two hybrid approaches. At two angles of attack （ 0~ and 8~ ）, the wall pressure fluctuations of the NACA0015 airfoil are computed. The obtained power spectra of the wall pressure fluctuations are analyzed and compared with the measured data. And the vortical structures around the airfoil at two angles of attack are simulated and analyzed. After that, the flow induced noises of the NACA0015 airfoil at two angles of attack are predicted by the two hybrid approaches （LES and FW-H, LES and Powell）. The radiated sound spectra are analyzed and compared with the experimental data. Comparisons show that both are robust, credible and satisfactory in the numerical prediction of the flow induced noise. All numerical simulations are carried out by parallel processing in the Wuxi supercomputing center.
基金the Key Research and Development Project of Shandong Province(2019GSF109084)Qilu University of Technology(Shandong Academy of Sciences)Young Doctors Cooperative Fund(2019BSHZ022).
文摘Centrifugal pumps are widely used in engineering for a variety of applications.A known drawback of these devices is the high-level noise generated during operations,which can affect their stability and adversely influence the entire working environment.By combining the Powell vortex sound theory,numerical simulations and experimental measurements,this research explores the trends of variation and the corresponding underlying mechanisms for the flow-induced noise at various locations and under different operating conditions.It is shown that the total sound source intensity(TSSI)and total sound pressure level(TSPL)in the impeller,in the region between the inlet to the outlet and along the circumferential extension of the volute,are much higher than those at pump inlet and outlet.Additionally,under various rotational speeds with the design flow rate(Condition 1),the TSSI and TSPL at pump inlet and outlet are higher than those obtained with the opening of the valve kept unchanged(Condition 2);vice versa when these two parameters are evaluated at various locations in the impeller and the volute under the Condition 2,they exceed the equivalent values obtained for the other Condition 1.
文摘In this paper, the measurement of an aerodynamic sound source for a semi-circular cylinder in a uniform flow is described using Particle Image Velocimetry (PIV). This experimental technique is based on vortex sound theory, where the time derivative of vorticity is evaluated with the aid of two sets of standard PIV systems. The experimental results indicate that the sound source for the semi-circular cylinder is located around the shear layer near the edge of the semi-circular cylinder. The sound source intensity and the area are reduced in the semi-circular cylinder compared with those of a circular cylinder. This result indicates that the aerodynamic sound of the semi- circular cylinder is smaller than that of the circular cylinder, which supports the microphone measurement result.
