Turbulent boundary layer control(TBLC) for skin-friction drag reduction is a relatively new technology made possible through the advances in computational-simulation capabilities,which have improved the understanding ...Turbulent boundary layer control(TBLC) for skin-friction drag reduction is a relatively new technology made possible through the advances in computational-simulation capabilities,which have improved the understanding of the flow structures of turbulence.Advances in micro-electronic technology have enabled the fabrication of active device systems able to manipulating these structures.The combination of simulation,understanding and micro-actuation technologies offers new opportunities to significantly decrease drag,and by doing so,to increase fuel efficiency of future aircraft.The literature review that follows shows that the application of active control turbulent skin-friction drag reduction is considered of prime importance by industry,even though it is still at a low technology readiness level(TRL).This review presents the state of the art of different technologies oriented to the active and passive control for turbulent skin-friction drag reduction and contributes to the improvement of these technologies.展开更多
In this paper,an analytical model that represents the streamwise velocity distribution for open channel flow with submerged flexible vegetation is studied.In the present vegetated flow modelling,the whole flow field h...In this paper,an analytical model that represents the streamwise velocity distribution for open channel flow with submerged flexible vegetation is studied.In the present vegetated flow modelling,the whole flow field has been separated into two layers vertically: a vegetated layer and a non-vegetated free-water layer.Within the vegetated layer,an analysis of the mechanisms affecting water flow through flexible vegetation has been conducted.In the non-vegetated layer,a modified log-law equation that represents the velocity profile varying with vegetation height has been investigated.Based on the studied analytical model,a sensitivity analysis has been conducted to assess the influences of the drag (CD) and friction (Cf ) coefficients on the flow velocity.The investigated ranges of CD and Cf have also been compared to published values.The findings suggest that the CD and Cf values are non-constant at different depths and vegetation densities,unlike the constant values commonly suggested in literature.This phenomenon is particularly clear for flows with flexible vegetation,which is characterised by large deflection.展开更多
基金supported by the European Commission though the Research and Innovation action DRAGY(Grant No.690623)the Ministry of Industry and Information Technology(MIIT)of the Chinese government
文摘Turbulent boundary layer control(TBLC) for skin-friction drag reduction is a relatively new technology made possible through the advances in computational-simulation capabilities,which have improved the understanding of the flow structures of turbulence.Advances in micro-electronic technology have enabled the fabrication of active device systems able to manipulating these structures.The combination of simulation,understanding and micro-actuation technologies offers new opportunities to significantly decrease drag,and by doing so,to increase fuel efficiency of future aircraft.The literature review that follows shows that the application of active control turbulent skin-friction drag reduction is considered of prime importance by industry,even though it is still at a low technology readiness level(TRL).This review presents the state of the art of different technologies oriented to the active and passive control for turbulent skin-friction drag reduction and contributes to the improvement of these technologies.
文摘In this paper,an analytical model that represents the streamwise velocity distribution for open channel flow with submerged flexible vegetation is studied.In the present vegetated flow modelling,the whole flow field has been separated into two layers vertically: a vegetated layer and a non-vegetated free-water layer.Within the vegetated layer,an analysis of the mechanisms affecting water flow through flexible vegetation has been conducted.In the non-vegetated layer,a modified log-law equation that represents the velocity profile varying with vegetation height has been investigated.Based on the studied analytical model,a sensitivity analysis has been conducted to assess the influences of the drag (CD) and friction (Cf ) coefficients on the flow velocity.The investigated ranges of CD and Cf have also been compared to published values.The findings suggest that the CD and Cf values are non-constant at different depths and vegetation densities,unlike the constant values commonly suggested in literature.This phenomenon is particularly clear for flows with flexible vegetation,which is characterised by large deflection.
