A numerical investigation is conducted to explore the evolution of a plasma discharge and its interaction with the fluid flow based on a self-consistent fluid model which couples the discharge dynamics with the fluid ...A numerical investigation is conducted to explore the evolution of a plasma discharge and its interaction with the fluid flow based on a self-consistent fluid model which couples the discharge dynamics with the fluid dynamics.The effects of the applied voltage on the distribution of velocity and temperature in initially static air are parainetrically studied.Furthermore,the spatial structure of plasma discharge and the resulting force contours in streamwise and normal directions are discussed in detail.The result shows that the plasma actuator produces a net force that should always be directed away from the exposed electrode,which results in an ionic wind pushing particles into a jet downstream of the actuator.When the energy added by the plasma is taken into account,the ambient air temperature is increased slightly around the electrode,but the velocity is almost not affected.Therefore it is unlikely that the induced flow is buoyancy driven.For the operating voltages considered in this paper,the maximum induced velocity is found to follow a power law,i.e.,it is proportional to the applied voltage to the 3.5 power.This promises an efficient application in the flow control with plasma actuators.展开更多
A one-dimensional(1D) fluid model of capacitive RF argon glow discharges between two parallel-plate electrodes at low pressure is employed. The influence of the secondary electron emission on the plasma characterist...A one-dimensional(1D) fluid model of capacitive RF argon glow discharges between two parallel-plate electrodes at low pressure is employed. The influence of the secondary electron emission on the plasma characteristics in the discharges is investigated numerically by the model. The results show that as the secondary electron emission coefficient increases,the cycle-averaged electric field has almost no change; the cycle-averaged electron temperature in the bulk plasma almost does not change, but it increases in the two sheath regions; the cycle-averaged ionization rate, electron density, electron current density, ion current density, and total current density all increase. Also, the cycle-averaged secondary electron fluxes on the surfaces of the electrodes increase as the secondary electron emission coefficient increases. The evolutions of the electron flux, the secondary electron flux and the ion flux on the powered electrode increase as the secondary electron emission coefficient increases. The cycle-averaged electron pressure heating, electron Ohmic heating, electron heating, and ion heating in the two sheath regions increase as the secondary electron emission coefficient increases. The cycle-averaged electron energy loss increases with increasing secondary electron emission coefficient.展开更多
The existing methods of computing the flow distribution in compound channels with flood plains have been summarized. A new method called the momentum-exchange method was presented and verified with experimental and fi...The existing methods of computing the flow distribution in compound channels with flood plains have been summarized. A new method called the momentum-exchange method was presented and verified with experimental and field data. The results show that the new method is more effective than previous ones.展开更多
The characteristics of the catchment discharge vary with land use. The characteristics of the long-term discharge of a terraced paddy field catchment were studied. Two kind of tank models for land use were proposed an...The characteristics of the catchment discharge vary with land use. The characteristics of the long-term discharge of a terraced paddy field catchment were studied. Two kind of tank models for land use were proposed and used to simulate the discharge of the catchment: one is a forest type model used as the upper part of the catchment; the other is a paddy field type model used as the lower part of the catchment. The results of the model simulation were analyzed and compared with that of a forest catchment.展开更多
Theoretical approach to the relation of different type of debris flow and curvature radius of discharge guide ditch and expression for estimating water surface freeboard, with the consideration of debris flow characte...Theoretical approach to the relation of different type of debris flow and curvature radius of discharge guide ditch and expression for estimating water surface freeboard, with the consideration of debris flow characteristics with rational structure, were described. The relevant formulae were simplified and verified by measurement data. The results show good coincidence of the estimated values with measured data.展开更多
Cavitation of orifices is one of the main problems of the Xiaolangdi flood discharge tunnels. Along with the decompression experiment, the flow field was calculated by using an axis-symmetrical κ-Ε turbulence model....Cavitation of orifices is one of the main problems of the Xiaolangdi flood discharge tunnels. Along with the decompression experiment, the flow field was calculated by using an axis-symmetrical κ-Ε turbulence model. The calculated pressure distribution was compared with the measured data and in agreement with each other. The calculated results show that few of the cavitation bubbles generating at the orifice edge can reach the wall under the calculation condition, the force applied on the orifice surface and the flow pattern before the orifice may be improved obviously by adding the vortex elimination ring at the upper side of the orifice.展开更多
Simulation of the mixing mechanism of submerged multiport diffusers used to discharge heated water from thermal-electric power plants and households into shallow receiving waters was described. The three-dimensional t...Simulation of the mixing mechanism of submerged multiport diffusers used to discharge heated water from thermal-electric power plants and households into shallow receiving waters was described. The three-dimensional turbulence model and hybrid finite analytic method were used to predict the behavior of near field for multiport buoyant jets in rivers. The predicted temperature dilution and velocity prove good by comparison with available laboratory measurements. An empirical formula for temperature dilution and velocity in near field for this kind of flow was given. The effect of parameters on the dilution behavior of multiple jets were also discussed.展开更多
This paper is concerned with the applications of water jet impact in air to energy dissipation. The scattered jet flow impinges into the downstream water plunge pool, which greatly improves the inflow condition of the...This paper is concerned with the applications of water jet impact in air to energy dissipation. The scattered jet flow impinges into the downstream water plunge pool, which greatly improves the inflow condition of the submerged jet in the pool and make it diffuse very quickly. The model experiments were conducted, which showed that a large jet flow could be scattered by a small one through impacting. The minimum discharge ratio for flow dispersion was studied. The unequal jet impact in air for energy dissipation was brought forward firstly in this paper as a new type of energy dissipator.展开更多
基金supported by the Foundation for Innovative Research Groups of National Natural Science Foundation of China(No.51121004)National Natural Science Foundation of China(No.50976026)
文摘A numerical investigation is conducted to explore the evolution of a plasma discharge and its interaction with the fluid flow based on a self-consistent fluid model which couples the discharge dynamics with the fluid dynamics.The effects of the applied voltage on the distribution of velocity and temperature in initially static air are parainetrically studied.Furthermore,the spatial structure of plasma discharge and the resulting force contours in streamwise and normal directions are discussed in detail.The result shows that the plasma actuator produces a net force that should always be directed away from the exposed electrode,which results in an ionic wind pushing particles into a jet downstream of the actuator.When the energy added by the plasma is taken into account,the ambient air temperature is increased slightly around the electrode,but the velocity is almost not affected.Therefore it is unlikely that the induced flow is buoyancy driven.For the operating voltages considered in this paper,the maximum induced velocity is found to follow a power law,i.e.,it is proportional to the applied voltage to the 3.5 power.This promises an efficient application in the flow control with plasma actuators.
基金Project supported by the National Natural Science Foundation of China(Grant No.51172101)
文摘A one-dimensional(1D) fluid model of capacitive RF argon glow discharges between two parallel-plate electrodes at low pressure is employed. The influence of the secondary electron emission on the plasma characteristics in the discharges is investigated numerically by the model. The results show that as the secondary electron emission coefficient increases,the cycle-averaged electric field has almost no change; the cycle-averaged electron temperature in the bulk plasma almost does not change, but it increases in the two sheath regions; the cycle-averaged ionization rate, electron density, electron current density, ion current density, and total current density all increase. Also, the cycle-averaged secondary electron fluxes on the surfaces of the electrodes increase as the secondary electron emission coefficient increases. The evolutions of the electron flux, the secondary electron flux and the ion flux on the powered electrode increase as the secondary electron emission coefficient increases. The cycle-averaged electron pressure heating, electron Ohmic heating, electron heating, and ion heating in the two sheath regions increase as the secondary electron emission coefficient increases. The cycle-averaged electron energy loss increases with increasing secondary electron emission coefficient.
基金The work was supported by National Natural Sciences Foudation of China, with which the an-thors won the third award of the Science and Technology Progress Prize of National Education Commissionin 1996.
文摘The existing methods of computing the flow distribution in compound channels with flood plains have been summarized. A new method called the momentum-exchange method was presented and verified with experimental and field data. The results show that the new method is more effective than previous ones.
文摘The characteristics of the catchment discharge vary with land use. The characteristics of the long-term discharge of a terraced paddy field catchment were studied. Two kind of tank models for land use were proposed and used to simulate the discharge of the catchment: one is a forest type model used as the upper part of the catchment; the other is a paddy field type model used as the lower part of the catchment. The results of the model simulation were analyzed and compared with that of a forest catchment.
文摘Theoretical approach to the relation of different type of debris flow and curvature radius of discharge guide ditch and expression for estimating water surface freeboard, with the consideration of debris flow characteristics with rational structure, were described. The relevant formulae were simplified and verified by measurement data. The results show good coincidence of the estimated values with measured data.
文摘Cavitation of orifices is one of the main problems of the Xiaolangdi flood discharge tunnels. Along with the decompression experiment, the flow field was calculated by using an axis-symmetrical κ-Ε turbulence model. The calculated pressure distribution was compared with the measured data and in agreement with each other. The calculated results show that few of the cavitation bubbles generating at the orifice edge can reach the wall under the calculation condition, the force applied on the orifice surface and the flow pattern before the orifice may be improved obviously by adding the vortex elimination ring at the upper side of the orifice.
文摘Simulation of the mixing mechanism of submerged multiport diffusers used to discharge heated water from thermal-electric power plants and households into shallow receiving waters was described. The three-dimensional turbulence model and hybrid finite analytic method were used to predict the behavior of near field for multiport buoyant jets in rivers. The predicted temperature dilution and velocity prove good by comparison with available laboratory measurements. An empirical formula for temperature dilution and velocity in near field for this kind of flow was given. The effect of parameters on the dilution behavior of multiple jets were also discussed.
文摘This paper is concerned with the applications of water jet impact in air to energy dissipation. The scattered jet flow impinges into the downstream water plunge pool, which greatly improves the inflow condition of the submerged jet in the pool and make it diffuse very quickly. The model experiments were conducted, which showed that a large jet flow could be scattered by a small one through impacting. The minimum discharge ratio for flow dispersion was studied. The unequal jet impact in air for energy dissipation was brought forward firstly in this paper as a new type of energy dissipator.