Noise reduction by collars applied to rod-airfoil was studied numerically. The flow field and acoustic far-field are predicted using a large eddy simulation the Ffowcs Williams Hawking analogy. present numerical method is first validated existing experimental results for baseline case. Then, reduce interaction noise, rod with designed (denoted as Col case). main noise mechanisms of investigated in detail. show that low- medium-frequency bands rod, which tonal reduced 24.83 dB. airfoil...

A general and simple calculation method is presented to investigate the effects of tube shape on resonant frequency performance a resonator. First, variable cross-section resonator modeled using transfer matrix. Then, amplification ratio pressure amplitude (ARPA), defined as at small end that large resonator, used evaluate its performance. The ARPA value for can be directly calculated from frequency. It shown closely related compression ratio. However, only determined by itself independent...

Variable camber is an effective method for improving the flight efficiency of large aircraft, and has attracted attention researchers. This work focused on optimization a variable airfoil. First, influences leading trailing edges airfoil aerodynamic performance were investigated using computational fluid dynamics numerical simulation. An initial database was established deep neural network. Second, iterative algorithm constructed to optimize in terms rotation angle edge, deflection position...

The acoustic streaming motion in a compressible air-filled two-dimensional cylindrical resonator driving by piston is simulated using the gas-kinetic scheme, and effects of field intensity on formation process flow structure as well pattern are investigated numerically for practical applications high-intensity devices. Therefore, five cases with different excitation amplitudes considered simulation ranging from linear to highly nonlinear regions. validation developed model verified comparing...

Nonlinear standing waves and acoustic streaming in an axial-symmetrical resonator with exponentially varying cross-sectional area were studied. A two-dimensional gas-kinetic Bhatnagar-Gross-Krook scheme based on the non-structure triangular grid was established to simulate nonlinear oscillations resonator. Details of transient steady flow fields developed. The effects winding index exponential-shape resonator, displacement amplitude piston streaming, vortex pattern analyzed. results...

A gas-kinetic scheme (GKS) based on an unstructured grid is applied to simulate the evolution of fluid motions in exponential variable cross-section resonators. The effects acoustic field intensity oscillatory pressure, velocity, temperature, and flow streaming structure were investigated numerically, model was validated. results demonstrate that geometry driving strength are main factors affecting final performance system. For quasi-linear moderate non-linear cases optimum tube, periodic...

Four subgrid-scale models based on large eddy simulation (LES), such as Smagorinsky–Lilly (SL), dynamic (DSL), wall-adapting local eddy-viscosity (WALE), and kinetic-energy transport (KET) were used couple Ffowcs Williams–Hawkings equation to accurately analyze identify the characteristics position of sound sources rod–airfoil interaction. The results four compared with experimental data. It was found that DSL model optimal for study interaction noise considering calculation accuracy....

The two-dimensional nonlinear acoustic oscillations in the resonator of four different driving amplitudes are simulated by a gas-kinetic scheme.The shock resonator, effects amplitude on field and flow distribution harmonics investigated based simulaton results.Moreover, this work discusses reasons for such as annular effect velocity reverse.It is pointed out that waveforms acoustics variables increasingly distort with driving-amplitude increasing.And it found under large-amplitude quite from...

The temporal-spatial evolution of gas oscillation was simulated by kinetic scheme (GKS) in a cylindrical resonator, driven piston at one end and rigidly closed the other end. Periodic shock waves propagating back forth were observed resonator under finite amplitude oscillation. studied results demonstrated that acoustic pressure is saw-tooth waveform oscillatory velocity square central position resonant tube. Moreover, it found harmonic analysis there no presence obvious feature for node...

A modified asymptotical regularization gradient method is presented for nonlinear ill-posed operator equations. Employing a priori and posteriori rules respectively, we obtain some convergence results under source condition. The stable with respect to perturbations of the If condition holds, optimal order rule. can be taken as generalization existing method. From method, many other convergent iterative methods constructed. Our numerical show that algorithm valid.

The temporal-spatial evolution of the sound field in a cylindrical resonator driven by piston was simulated gas-kinetic scheme (GKS), and periodic shock waves propagating back forth were observed with finite displacement amplitude driving piston. It can been seen from instantaneous spatial distribution oscillatory pressure velocity that is one-dimensional,but exhibits quasi-one-dimensional due to effect boundary layer.The process wave sinusoidal zigzag demonstrated increasing Especially,...

A periodic square-wave structure was designed on the cylinder surface to control interaction noise of tandem double cylinders. Experiments were carried out measure and flow field with particle image velocimetry technique in a 0.55 × 0.4 m acoustic wind tunnel. The influences different parameters reduction mechanism investigated. incoming velocity is range 20–80 m/s. experimental results show that cylindrical can significantly reduce cylinders, sound pressure level mainly middle-...

Objectives  As the deflection angle has great influence on temperature and noise radiation near deflector of impinging jet a carrier-based aircraft, determining an appropriate can expand safe area around aircraft. Methods  This paper analyzes flow field, field sound characteristics certain type engine tail nozzle in full afterburner conditions under different angles (β=35°, 45°, 55°) monitoring distances (S=20D, 30D, 50D, 80D). Using large eddy simulation (LES) acoustic analogy methods,...