The influence of sand dust on discharge of external insulation has caused widespread concern.At present,the research results show wind-sand electricity has a remarkable effect on the discharge characteristics of insul...The influence of sand dust on discharge of external insulation has caused widespread concern.At present,the research results show wind-sand electricity has a remarkable effect on the discharge characteristics of insulator and has little influence on the discharge characteristics of air gap.The flashover of insulator strings occurs along the insulator surface and air gaps,and the sand dust deposited on the insulator surface may affect the flashover characteristics of insulator strings.This paper studies the flashover characteristics of flat plate model under DC voltage in wind-sand condition.The experimental results show that under positive polarity voltage,the flashover voltage of the flat plate model has a maximum value,while under negative polarity voltage,the flashover voltage of the flat plate model has a minimum value with a certain degree of sand dust deposition.The wind or sand in sand-dust weather has an important effect on the flashover characteristics of the flat plate model.In certain variation range of electric charge,electric charge of sand dust has little effect on the flashover voltage of flat plate model under DC voltage.The deposition of sand has significant influence on the flashover process of flat plate model,which is related to the deposition density and moisture content of sand particle.展开更多
A new turbulent constitutive relation was directly derived from Boussinesqs hypothesis and mixing length theory,and then implemented in the standard k-ε model.The performance of this constitutive relation was valid...A new turbulent constitutive relation was directly derived from Boussinesqs hypothesis and mixing length theory,and then implemented in the standard k-ε model.The performance of this constitutive relation was validated in zero pressure gradient flat-plate boundary layer flow,fully-developed turbulent channel flow and separated flow in a plane asymmetric diffuser.The investigation demonstrated that,this new constitutive relation gave very accurate results in the former two basic cases and provided significant improvement in prediction of separated and reattachment points in the plane asymmetric diffuser.Separation and reattachment points at x/H =7.5and 29 were calculated accurately in comparison to experimental results,and the static pressure coefficient of 0.82 was very close to large eddy simulation calculation.These results are very encouraging but further verification and extensive application of the new constitutive relation to other two-equation eddy viscosity model are needed.展开更多
基金Project Supported by National Natural Science Foundation of China（90510014 ）.
文摘The influence of sand dust on discharge of external insulation has caused widespread concern.At present,the research results show wind-sand electricity has a remarkable effect on the discharge characteristics of insulator and has little influence on the discharge characteristics of air gap.The flashover of insulator strings occurs along the insulator surface and air gaps,and the sand dust deposited on the insulator surface may affect the flashover characteristics of insulator strings.This paper studies the flashover characteristics of flat plate model under DC voltage in wind-sand condition.The experimental results show that under positive polarity voltage,the flashover voltage of the flat plate model has a maximum value,while under negative polarity voltage,the flashover voltage of the flat plate model has a minimum value with a certain degree of sand dust deposition.The wind or sand in sand-dust weather has an important effect on the flashover characteristics of the flat plate model.In certain variation range of electric charge,electric charge of sand dust has little effect on the flashover voltage of flat plate model under DC voltage.The deposition of sand has significant influence on the flashover process of flat plate model,which is related to the deposition density and moisture content of sand particle.
基金China Academy of Aeronautics Propulsion Innovation Fund
文摘A new turbulent constitutive relation was directly derived from Boussinesqs hypothesis and mixing length theory,and then implemented in the standard k-ε model.The performance of this constitutive relation was validated in zero pressure gradient flat-plate boundary layer flow,fully-developed turbulent channel flow and separated flow in a plane asymmetric diffuser.The investigation demonstrated that,this new constitutive relation gave very accurate results in the former two basic cases and provided significant improvement in prediction of separated and reattachment points in the plane asymmetric diffuser.Separation and reattachment points at x/H =7.5and 29 were calculated accurately in comparison to experimental results,and the static pressure coefficient of 0.82 was very close to large eddy simulation calculation.These results are very encouraging but further verification and extensive application of the new constitutive relation to other two-equation eddy viscosity model are needed.
