The pre-multiplied spanwise energy spectra of streamwise velocity fluctuations are investigated in this paper. Two distinct spectral peaks in the spanwise spectra are observed in low-Reynolds-number wall-bounded turbu...The pre-multiplied spanwise energy spectra of streamwise velocity fluctuations are investigated in this paper. Two distinct spectral peaks in the spanwise spectra are observed in low-Reynolds-number wall-bounded turbulence. The spectra are calculated from direct numerical simulation （DNS） of turbulent channel flows and zero-pressure-gradient boundary layer flows. These two peaks locate in the nearwall and outer regions and are referred to as the inner peak and the outer peak, respectively. This result implies that the streamwise velocity fluctuations can be separated into large and small scales in the spanwise direction even though the friction Reynolds number Rer can be as low as 1000. The properties of the inner and outer peaks in the spanwise spec- tra are analyzed. The locations of the inner peak are invariant over a range of Reynolds numbers. However, the locations of the outer peak are associated with the Reynolds number, which are much higher than those of the outer peak of the pre-multiplied streamwise energy spectra of the streamwise velocity.展开更多
The directivity of the noise generated by turbulent flows around an underwater vehicle(the fully appended SUBOFF body)is investigated numerically,where the turbulent flows are simulated by using the large eddy simulat...The directivity of the noise generated by turbulent flows around an underwater vehicle(the fully appended SUBOFF body)is investigated numerically,where the turbulent flows are simulated by using the large eddy simulation(LES)with a non-equilibrium wall model and the noise is calculated by using the Ffowcs Williams and Hawking formulation.The wall-modeled LES reproduces the features of turbulent flows around SUBOFF,such as the attached boundary layers around the hull,separated vortices from appendages and the wrapped vortices in wakes.The coefficients and power spectral density of the wall pressures obtained are in agreement with the previous numerical results and experimental measurements.It is found that the constructive and destructive interferences of lift and side-force dipoles lead to the deviations of the directivities of instantaneous sound pressures from the lift directions.This is different from noise generated by flows around a circular cylinder,where lift dipoles dominate the radiated noise.展开更多
基金supported by the National Natural Science Foundation of China (Grants 11302238, 11232011, 11572331, and 11490551)the support from the Strategic Priority Research Program (Grant XDB22040104)+1 种基金the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences (Grant QYZDJ-SSW-SYS002)the National Basic Research Program of China (973 Program 2013CB834100 : Nonlinear Science)
文摘The pre-multiplied spanwise energy spectra of streamwise velocity fluctuations are investigated in this paper. Two distinct spectral peaks in the spanwise spectra are observed in low-Reynolds-number wall-bounded turbulence. The spectra are calculated from direct numerical simulation （DNS） of turbulent channel flows and zero-pressure-gradient boundary layer flows. These two peaks locate in the nearwall and outer regions and are referred to as the inner peak and the outer peak, respectively. This result implies that the streamwise velocity fluctuations can be separated into large and small scales in the spanwise direction even though the friction Reynolds number Rer can be as low as 1000. The properties of the inner and outer peaks in the spanwise spec- tra are analyzed. The locations of the inner peak are invariant over a range of Reynolds numbers. However, the locations of the outer peak are associated with the Reynolds number, which are much higher than those of the outer peak of the pre-multiplied streamwise energy spectra of the streamwise velocity.
基金the National Natural Science Foundation of China(Grant Nos.11988102,11922214).
文摘The directivity of the noise generated by turbulent flows around an underwater vehicle(the fully appended SUBOFF body)is investigated numerically,where the turbulent flows are simulated by using the large eddy simulation(LES)with a non-equilibrium wall model and the noise is calculated by using the Ffowcs Williams and Hawking formulation.The wall-modeled LES reproduces the features of turbulent flows around SUBOFF,such as the attached boundary layers around the hull,separated vortices from appendages and the wrapped vortices in wakes.The coefficients and power spectral density of the wall pressures obtained are in agreement with the previous numerical results and experimental measurements.It is found that the constructive and destructive interferences of lift and side-force dipoles lead to the deviations of the directivities of instantaneous sound pressures from the lift directions.This is different from noise generated by flows around a circular cylinder,where lift dipoles dominate the radiated noise.
