In order to meet the requirements of low dispersive and low dissipative numerical discretization schemes in computational aero-acoustics
the spectral element method combined with Lighthill's acoustic analogy theory for the simulation of aeroacoustic problems is investigated. Taking the second temporal derivative of pseudopressure as the source of the inhomogeneous wave equation
and space discretization using spectral element method time discretization using implicit Newmark method
under the C-E-M absorbing boundary condition the acoustic field generated by a co-rotating spinning vortex pair is solved. This co-rotating vortex pair consists of two point vortices separated by a fixed distance of 2r
0
with a circulation intensity Γ. The incom
pressible flow field is obtained using the complex potential theory
and the acoustic source terms are computed using these hydrodynamic quantities. The acoustic pressure results are evaluated by comparing them with the analytical solution obtained from the matched asymptotic expansion(MAE)method The numerical solutions are in good agreement with the analytical solutions. The results show that the spectral element method can obtain high accuracy using only eleven grids in one wavelength. In the case of the same number of grids
the smaller the time step
the smaller the error between numerical solution and analytical solution. Finally
it is proved that the aero-acoustic problems induced by incompressible flows can be solved with high accuracy by using the second temporal derivative of the pseudopressure as the acoustic source.
LI Xiaodong, JIANG Min, GAO Junhui, et al. Progress and prospective of computational aeroacoustics [J]. Science China: Physics, Mechanics & Astronomy, 2014(3): 234-248.
LELE S K, NICHOLS J W. A second golden age of aeroacoustics [J]. Philosophical Transactions of the Royal Society of London: A Mathematical, Physical and Engineering Sciences, 2014, 372(2022): 20130321.
GIVOLI D. High-order local non-reflecting boundary conditions: a review [J]. Wave Motion, 2004, 39(4): 319-326.
DAHL M D. Numerical solutions to the fourth and second computational aeroacoustics(CAA)workshop benchmark problems [C]∥The 4th Computational Aeroacoustics(CAA)Workshop on Benchmark Problems. Washington, DC, USA: NASA Glenn Research Center, 2004: 187-197.
XU Kangle, CHEN Yingchun, TAO Jun, et al. A splitting simulation method for aeroacoustic at low Mach conditions [J]. Journal of Fudan University(Natural Science), 2014, 53(5): 636-644.
HÜPPE A, KALTENBACHER M. Spectral finite elements for computational aeroacoustics using acoustic perturbation equations [J]. Journal of Computational Acoustics, 2012, 20(2): 1240005.
ALI I, ESCOBAR M, KALTENBACHER M, et al. Time domain computation of flow induced sound [J]. Computers Fluids, 2008, 37(4): 349-359.
ZHU W J, SHEN W Z, SØRENSEN J N. High-order numerical simulations of flow-induced noise [J]. International Journal for Numerical Methods in Fluids, 2011, 66(1): 17-37.
HARDIN J, POPE D. An acoustic/viscous splitting technique for computational aeroacoustics [J]. Theoretical and Computational Fluid Dynamics, 1994, 6(5/6): 323-340.
FARSHCHI M, HANNANI S K, EBRAHIMI M. Linearized and nonlinear acoustic/viscous splitting techniques for low Mach number flows [J]. International Journal for Numerical Methods in Fluids, 2003, 42(10): 1059-1072.
EKATERINARIS J A. New formulation of Hardin-Pope equations for aeroacoustics [J]. AIAA Journal, 1999, 37(9): 1033-1039.
EKATERINARIS J A. An upwind scheme for the computation of acoustic field generated by incompressible flow [J]. AIAA Journal, 1997, 35(1): 14481455.
ZHU C, QIN G, ZHANG J. Implicit Chebyshev spectral element method for acoustics wave equations [J]. Finite Elements in Analysis and Design, 2011, 47(2): 184-194.
ZHANG R, QIN G, ZHU C. Spectral element method for acoustic propagation problems based on linearized Euler equations [J]. Journal of Computational Acoustics, 2009, 17(4): 383-402.
RIBNER H S. The generation of sound by turbulent jets [J]. Advances in Applied Mechanics, 1964, 8: 103182.
PAPAGEORGAKOPOULOS J, TSANGARIS S. A numerical method for predicting acoustical wave propagation in open spaces [J/OL]. [2016-04-06]. https:∥www.hindawi.com/journals/isrn/2011/174031/abs/.
CLAYTON R, ENGQUIST B. Absorbing boundary conditions for acoustic and elastic wave equations [J]. Bulletin of Seismological Society of America, 1977, 67(6): 1529-1540.
ZHANG Rongxin, QIN Guoliang. Chebychev spectral elements method for acoustic propagation problem in a uniform mean flow [J]. Journal of Xi'an Jiaotong University, 2009, 43(7): 120-124.
LEE D J, KOO S O. Numerical study of sound generation due to a spinning vortex pair [J]. AIAA Journal, 1995, 33(1): 20-26.