In this paper, an experimental investigation of a Iaminar wall jet in the presence of a heated wall with stationary particles on its surface, is reported. The wall jet was submitted to external acoustic vibrations amp...In this paper, an experimental investigation of a Iaminar wall jet in the presence of a heated wall with stationary particles on its surface, is reported. The wall jet was submitted to external acoustic vibrations amplifying the coherent structures appearing in the laminar region. A wind tunnel was used at very low Reynolds number. Mean velocity and turbulence intensity were measured by a constant temperature anemometer. Measurements were taken in the transition and turbulent regions. Embedded particles were outside the viscous sublayer and it was observed that their presence modifies significantly the flow characteristics in particular the boundary layer is thickened. This study can bring a better understanding of the structure of a flow when it is heated and forced on a rough wall.展开更多
The characteristics of a laminar wall jet submitted to different configurations have been experimentally explored in order to obtain a better knowledge of transition modifications,In fact different parameters can acce...The characteristics of a laminar wall jet submitted to different configurations have been experimentally explored in order to obtain a better knowledge of transition modifications,In fact different parameters can accelerate or delay the transition using a smooth or rough surface,heated or not,submitted to vibrations or not .In this study,significant effects can be noticed.It has been possible to measure the beginning of growth rates of disturbance amplitude using a wind tunnel and comparing the results with the linear stability theory.展开更多
There are similarities between planes and birds. In fact aerodynamics bases are the same. In order to make some comparisons, this paper presents two series of experiments ： one in a wind tunnel with an omithopter mod...There are similarities between planes and birds. In fact aerodynamics bases are the same. In order to make some comparisons, this paper presents two series of experiments ： one in a wind tunnel with an omithopter model for measurements of aerodynamic forces with flapping wings. The wing movement has two degrees of freedom flapping around the longitudinal axis of the model and feathering around the wing axis. Measurements of aerodynamic forces： rift and drag in static case averaging values during many cycles of movement and in dynamic case have been performed. The other part of the paper concerns velocity and turbulence measurements on a metal plane wall jet in a wind tunnel with and without a rough surface, with and without acoustic vibrations in order to simulate a plane wing. Aerodynamic characteristics have been obtained in all cases.展开更多
文摘In this paper, an experimental investigation of a Iaminar wall jet in the presence of a heated wall with stationary particles on its surface, is reported. The wall jet was submitted to external acoustic vibrations amplifying the coherent structures appearing in the laminar region. A wind tunnel was used at very low Reynolds number. Mean velocity and turbulence intensity were measured by a constant temperature anemometer. Measurements were taken in the transition and turbulent regions. Embedded particles were outside the viscous sublayer and it was observed that their presence modifies significantly the flow characteristics in particular the boundary layer is thickened. This study can bring a better understanding of the structure of a flow when it is heated and forced on a rough wall.
文摘The characteristics of a laminar wall jet submitted to different configurations have been experimentally explored in order to obtain a better knowledge of transition modifications,In fact different parameters can accelerate or delay the transition using a smooth or rough surface,heated or not,submitted to vibrations or not .In this study,significant effects can be noticed.It has been possible to measure the beginning of growth rates of disturbance amplitude using a wind tunnel and comparing the results with the linear stability theory.
文摘There are similarities between planes and birds. In fact aerodynamics bases are the same. In order to make some comparisons, this paper presents two series of experiments ： one in a wind tunnel with an omithopter model for measurements of aerodynamic forces with flapping wings. The wing movement has two degrees of freedom flapping around the longitudinal axis of the model and feathering around the wing axis. Measurements of aerodynamic forces： rift and drag in static case averaging values during many cycles of movement and in dynamic case have been performed. The other part of the paper concerns velocity and turbulence measurements on a metal plane wall jet in a wind tunnel with and without a rough surface, with and without acoustic vibrations in order to simulate a plane wing. Aerodynamic characteristics have been obtained in all cases.
