2/19/2024 0 Comments Sound diffraction clear gas![]() In addition, many scholars aim to develop accurate prediction methods of flow-induced noise using the cylinder–airfoil model. L is the distance between the cylinder and the airfoil, and d represents the airfoil’s diameter. 17 used the high-order implicit LES method to simulate the noise of different cylinder–airfoil configurations and found that the influence of fluid resonance was stronger and the noise level was more significant when L/ d = 6 and 10. 11 studied the noise generated by the wing in the wake of a cylinder at a low Mach number and found that the Gaussian spanwise coherence loss caused by vortex shedding significantly influenced the broadband noise. The results show that the cylindrical wake’s volume source plays a vital role at high frequencies. 16 used DES (Detached-Eddy Simulation) and FW–H acoustic simulation formulas to calculate the far field and numerically predicted the noise generated by the airfoil in the cylindrical wake. It was found that the Dynamic Smagorinsky–Lilly (DSL) model is the best sub-grid scale model to study the interaction noise. 15 accurately analyzed and identified the sound source characteristics and location of the interaction between the cylinder and airfoil. Then, based on four sub-grid scale models of LES and FW–H equation, Yang et al. Some additional quadrupole sound sources could be seen at low and high frequencies. It found that the dipole noise radiation was dominant at the shedding frequency of the cylindrical vortex and its harmonics. ![]() ![]() 14 studied the noise generated by the cylindrical–airfoil structure using unstructured large-eddy simulation coupled with an FW–H technique. 13 used the internally developed solver SPARC (Scalable Processor Architecture) and many turbulence models with different spatial discrete formats to simulate and focus on the influence of various models and coefficients of computational fluid dynamics on far-field sound prediction. The calculated far-field sound spectrum agrees with the measured values in the attached experiment. 11 calculated the flow field information by two-dimensional RANS (Reynolds-Averaged Navier-Stokes) and combined it with Ffowcs Williams–Hawkins (FW–H) equation 12 to obtain noise data. Currently, the primary numerical simulation method to study aerodynamic noise is the computational fluid dynamics (CFD)/Computational Acoustics (CA) method, a hybrid algorithm of computational fluid dynamics (CFD) 8–10 and Computational Acoustics (CA). In recent years, computational acoustics has become the preferred tool for noise prediction, rather than time-consuming experiments or expensive post-design processing. The research helps understand the vortex acoustic coupling mechanism of the cylinder–airfoil model and provides a more accurate numerical prediction of flow-induced noise. The calculated results of the vortex sound theory are closer to the experimental ones than the FW–H method. The results show that the vortex shedding from the cylinder and the interaction between vortex shedding and airfoil have the greatest influence on the acoustic, and the far-field noise of the cylinder airfoil shows a partial “eight” dipole distribution. The flow-induced noise prediction results are finally compared with Ffowcs Williams–Hawkings (FW–H) acoustic analogy approach. The vortex structures around the cylinder airfoil are identified and captured by the Q-criterion for further analysis of vortex–noise correlation mechanism. The large eddy simulation method is adopted to solve the unsteady flow, and the acoustic information is then calculated using the vortex acoustic equation at each iteration step. To start with the derivation of Powell’s vortex sound equation, an implicit three-dimensional model of the fluid–acoustic coupling field is established to process the unsteady iterative calculation. The classical cylindrical–airfoil interference model is used to perform the simulation and compared with the experimental results. An innovative numerical prediction method of flow-induced noise is implemented to overcome the defect that the traditional acoustic analogy method cannot reflect the interaction between turbulence vortex and sound.
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