A discussion is made of the wind force coefficients for designing the main wind force resisting systems of H.P. （Hyperbolic-Paraboid）-shaped porous canopy roofs on the basis of a wind tunnel experiment. Roof models ...A discussion is made of the wind force coefficients for designing the main wind force resisting systems of H.P. （Hyperbolic-Paraboid）-shaped porous canopy roofs on the basis of a wind tunnel experiment. Roof models with a number of small circular holes were made of nylon resin using laser lithography. The porosity was changed from 0 （solid） to 0.4. Besides the porosity, the geometric parameters of the models were the rise to span ratio and slope of the roof. The overall aerodynamic forces and moments acting on a model were measured by a six-component force balance in a turbulent boundary layer. The results indicate that the porosity significantly reduces the wind loads. The design wind force coefficients for porous canopy roofs can be provided by those for solid roofs with the same configuration multiplied by a reduction factor. The proposed wind force coefficients are verified by a comparison of the load effect predicted by the proposed wind force coefficients with the maximum load effect obtained from dynamic analyses using the time history of wind force and moment coefficients. The axial forces induced in the columns supporting the roof are regarded as the load effect for discussing the design wind loads.展开更多
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
文摘A discussion is made of the wind force coefficients for designing the main wind force resisting systems of H.P. （Hyperbolic-Paraboid）-shaped porous canopy roofs on the basis of a wind tunnel experiment. Roof models with a number of small circular holes were made of nylon resin using laser lithography. The porosity was changed from 0 （solid） to 0.4. Besides the porosity, the geometric parameters of the models were the rise to span ratio and slope of the roof. The overall aerodynamic forces and moments acting on a model were measured by a six-component force balance in a turbulent boundary layer. The results indicate that the porosity significantly reduces the wind loads. The design wind force coefficients for porous canopy roofs can be provided by those for solid roofs with the same configuration multiplied by a reduction factor. The proposed wind force coefficients are verified by a comparison of the load effect predicted by the proposed wind force coefficients with the maximum load effect obtained from dynamic analyses using the time history of wind force and moment coefficients. The axial forces induced in the columns supporting the roof are regarded as the load effect for discussing the design wind loads.
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.
