As a promising means,the passive porosity technology is used for the trailing-edge noise reduction of a bionic airfoil.The detailed two-dimensional Large Eddy Simulation is achieved to gain a better understanding of t...As a promising means,the passive porosity technology is used for the trailing-edge noise reduction of a bionic airfoil.The detailed two-dimensional Large Eddy Simulation is achieved to gain a better understanding of the prediction and passive control of trailing-edge noise source with the non-porous and porous treatment,respectively.The flow fields around the bionic airfoil indicate that the leading-edge separation causes both the noise contributors,i.e.,the turbulent boundary layer and the vortex shedding.In addition,the effect of the porous trailing edge is substantiated in the distribution of the static pressure.The relevant noise also suggests a pronounced noise reduction potential in excess of 10 dB,but it has dependence on the flow resistivities.The two trailing-edge noise reduction mechanisms are characterized:(1)the suppression of the tonal vortex shedding noise;(2)the reduction of broadband turbulent boundary layer scattering noise.The findings may be used as reference in the design of silent aircraft.展开更多
With the increase of blade loading, the loss prediction model used in the design process needs refinement and improvement to meet the high-performance design. For the turbine design, most of existing profile loss mode...With the increase of blade loading, the loss prediction model used in the design process needs refinement and improvement to meet the high-performance design. For the turbine design, most of existing profile loss models are developed for subsonic and transonic cases and their accuracy in high Mach number flow are limited. The primary research interest of this work is to study the flow mechanism of turbine cascade with high Mach number and the related profile loss. In this work, a transonic turbine cascade with strong shock wave is numerically studied with Reynolds Averaged Navier-Stokes(RANS). Also, to overcome the limitations of RANS modeling, Delayed Detached Eddy Simulation(DDES) type high-fidelity turbulence simulation is also conducted. Based on the numerical results, the primary loss sources, including the boundary layer loss, the trailing loss and the shock loss are analyzed and results from existing loss models are assessed. The results from current work may help to develop refinement profile loss model for the design of turbine cascade working in the high Mach number regime.展开更多
Noise prediction from streamlined bodies such as wind turbine blades can be predicted accurately using CFD computations that use spatio-temporal turbulence models at the expense of high computational power.In this wor...Noise prediction from streamlined bodies such as wind turbine blades can be predicted accurately using CFD computations that use spatio-temporal turbulence models at the expense of high computational power.In this work,empirical methods proposed from BPM,Grosveld and Lowson are used to compute numerically to analyse the influence of rotor solidity factor on broadband trailing edge noise from a 2 MW horizontal axis wind turbine with a blade length of 37 m.Inputs to acoustic solver are the velocity vector field and boundary layer data which are obtained using blade element momentum and X-Foil.The outputs from acoustic solver are directivity and far field sound pressure on a receiver located at distance of 120m from tower base.The results have shown that for a wind speed of 10 m/s measured at 10m above ground,sound power level was found to increase between mid-bands to high frequencies for all three methods.Rotor solidity effect was illustrated at constant rotational speed of 17 RPM and receiver height of 0.5m located in downwind position.A minimum difference of 1.5dBA was found at f~100 Hz for Lowson method and maximum of~2.8dBA at 1 kHz between two and three blade rotor.For BPM and Grosveld methods however,the sound levels were~5dBA lower for two blade rotor than three blade rotor between f~100 Hz and f~1 kHz.The study also demonstrated that as number of blades increase by integral multiples,the effect on noise radiation from trailing edge of blades increase by 2-5dBA due to amplitude modulation.展开更多
基金supported by the National Natural Science Fundation of China(Major Project of International Cooperation)(Grant No.50920105504)
文摘As a promising means,the passive porosity technology is used for the trailing-edge noise reduction of a bionic airfoil.The detailed two-dimensional Large Eddy Simulation is achieved to gain a better understanding of the prediction and passive control of trailing-edge noise source with the non-porous and porous treatment,respectively.The flow fields around the bionic airfoil indicate that the leading-edge separation causes both the noise contributors,i.e.,the turbulent boundary layer and the vortex shedding.In addition,the effect of the porous trailing edge is substantiated in the distribution of the static pressure.The relevant noise also suggests a pronounced noise reduction potential in excess of 10 dB,but it has dependence on the flow resistivities.The two trailing-edge noise reduction mechanisms are characterized:(1)the suppression of the tonal vortex shedding noise;(2)the reduction of broadband turbulent boundary layer scattering noise.The findings may be used as reference in the design of silent aircraft.
基金National Natural Science Foundation of China(No.51506107,No.51476082)
文摘With the increase of blade loading, the loss prediction model used in the design process needs refinement and improvement to meet the high-performance design. For the turbine design, most of existing profile loss models are developed for subsonic and transonic cases and their accuracy in high Mach number flow are limited. The primary research interest of this work is to study the flow mechanism of turbine cascade with high Mach number and the related profile loss. In this work, a transonic turbine cascade with strong shock wave is numerically studied with Reynolds Averaged Navier-Stokes(RANS). Also, to overcome the limitations of RANS modeling, Delayed Detached Eddy Simulation(DDES) type high-fidelity turbulence simulation is also conducted. Based on the numerical results, the primary loss sources, including the boundary layer loss, the trailing loss and the shock loss are analyzed and results from existing loss models are assessed. The results from current work may help to develop refinement profile loss model for the design of turbine cascade working in the high Mach number regime.
文摘Noise prediction from streamlined bodies such as wind turbine blades can be predicted accurately using CFD computations that use spatio-temporal turbulence models at the expense of high computational power.In this work,empirical methods proposed from BPM,Grosveld and Lowson are used to compute numerically to analyse the influence of rotor solidity factor on broadband trailing edge noise from a 2 MW horizontal axis wind turbine with a blade length of 37 m.Inputs to acoustic solver are the velocity vector field and boundary layer data which are obtained using blade element momentum and X-Foil.The outputs from acoustic solver are directivity and far field sound pressure on a receiver located at distance of 120m from tower base.The results have shown that for a wind speed of 10 m/s measured at 10m above ground,sound power level was found to increase between mid-bands to high frequencies for all three methods.Rotor solidity effect was illustrated at constant rotational speed of 17 RPM and receiver height of 0.5m located in downwind position.A minimum difference of 1.5dBA was found at f~100 Hz for Lowson method and maximum of~2.8dBA at 1 kHz between two and three blade rotor.For BPM and Grosveld methods however,the sound levels were~5dBA lower for two blade rotor than three blade rotor between f~100 Hz and f~1 kHz.The study also demonstrated that as number of blades increase by integral multiples,the effect on noise radiation from trailing edge of blades increase by 2-5dBA due to amplitude modulation.
