Research interests have recently been directed towards electrical discharges in multi-phase environments.Natural electrical discharges,such as lightning and coronas,occur in the Earth＇s atmosphere,which is actually a...Research interests have recently been directed towards electrical discharges in multi-phase environments.Natural electrical discharges,such as lightning and coronas,occur in the Earth＇s atmosphere,which is actually a mixture of gaseous phase（air） and suspended solid and liquid particulate matters（PMs）.An example of an anthropogenic gaseous multi-phase environment is the flow of flue gas through electrostatic precipitators（ESPs）,which are generally regarded as a mixture of a post-combustion gas with solid PM and microdroplets suspended in it.Electrical discharges in multi-phase environments,the knowledge of which is scarce,are becoming an attractive research subject,offering a wide variety of possible discharges and multi-phase environments to be studied.This paper is an introduction to electrical discharges in multi-phase environments.It is focused on DC negative coronas and accompanying electrohydrodynamic（EHD） flows in a gaseous two-phase fluid formed by air（a gaseous phase） and solid PM（a solid phase）,run under laboratory conditions.The introduction is based on a review of the relevant literature.Two cases will be considered：the first case is of a gaseous two-phase fluid,initially motionless in a closed chamber before being subjected to a negative corona（with the needle-toplate electrode arrangement）,which afterwards induces an EHD flow in the chamber,and the second,of a gaseous two-phase fluid flowing transversely with respect to the needle-to-plate electrode axis along a chamber with a corona discharge running between the electrodes.This review-based introductory paper should be of interest to theoretical researchers and modellers in the field of negative corona discharges in single-or two-phase fluids,and for engineers who work on designing EHD devices（such as ESPs,EHD pumps,and smoke detectors）.展开更多
An electrohydrodynamic （EHD） method, which is based on glow discharge plasma, is presented for flow control in an S-shaped duct. The research subject is an expanding channel with a constant width and a rectangular c...An electrohydrodynamic （EHD） method, which is based on glow discharge plasma, is presented for flow control in an S-shaped duct. The research subject is an expanding channel with a constant width and a rectangular cross section. An equivalent divergence angle and basic function are introduced to build the three-dimensional model. Subsequently, the plasma physical models are simplified as the effects of electrical body force and work （done by the force） on the fluid near the wall. With the aid of FLUENT software, the source terms of momentum and energy are added to the Navier-Stokes equation. Finally, the original performance of three models （A, B and C） is studied, in which model A demonstrates better performance. Then EHD control based on model A is discussed. The results show that the EHD method is an effective way of reducing flow loss and improving uniformity at the duct exit. The innovation in this study is the assessment of the EHD control effect on the flow in an S-shaped duct. Both the parametric modeling of the S-shaped duct and the simplified models of plasma provide valuable information for future research on aircraft inlet ducts.展开更多
In previous studies, the nonlinear problem of electrohydrodynamic(EHD)ion drag flows in a circular cylindrical conduit has been studied by several authors. However, those studies seldom involve the computation for lar...In previous studies, the nonlinear problem of electrohydrodynamic(EHD)ion drag flows in a circular cylindrical conduit has been studied by several authors. However, those studies seldom involve the computation for large physical parameters such as the electrical Hartmann number and the magnitude parameter for the strength of the nonlinearity due to the existence of strong nonlinearity in these extreme cases. To overcome this faultiness, the newly-developed homotopy Coiflets wavelet method is extended to solve this EHD flow problem with strong nonlinearity. The validity and reliability of the proposed technique are verified. Particularly, the highly accurate homotopy-wavelet solution is obtained for extreme large parameters, which seems to be overlooked before.Discussion about the effects of related physical parameters on the axial velocity field is presented.展开更多
Based on the theory of EHD （electronhydrodynamic）, a simplified volume force model is applied to simulation to analyze the traits of plasma flow control in flow field, in which the cold plasma is generated by a DBD ...Based on the theory of EHD （electronhydrodynamic）, a simplified volume force model is applied to simulation to analyze the traits of plasma flow control in flow field, in which the cold plasma is generated by a DBD （dielectric-barrier-discharge） actuator. With the para- electric action of volume force in electric field, acceleration characteristics of the plasma flow are investigated for different excitation intensities of RF （radio frequency） power for the actuator. Furthermore, the plasma acceleration leads to an asymmetric distribution of flow field, and hence induces the deflection of jet plume, then results in a significant deflection angle of 6.26° thrustvectoring effect. It appears that the plasma flow control technology is a new tentative method for the thrust-vectoring control of a space vehicle.展开更多
In this Paper, we have proposed a new weighted residual method known as orthogonal collocation-based on mixed interpolation (OCMI). Mixed interpolation uses the classical polynomial approximation with two correction t...In this Paper, we have proposed a new weighted residual method known as orthogonal collocation-based on mixed interpolation (OCMI). Mixed interpolation uses the classical polynomial approximation with two correction terms given in the form of sine and cosine function. By these correction terms, we can control the error in the solution. We have applied this approach to a non-linear boundary value problem (BVP) in ODE which governs the electrohydrodynamic flow in a cylindrical conduit. The solution profiles shown in the figures are in good agreement with the work of Paullet (1999) and Ghasemi et al. (2014). Our solution is monotonic decreasing and satisfies , where, α governs the strength of non-linearity and for large values of α solutions are . The residual errors are given in Table 1 and Table 2 which are significantly small. Comparison of residual errors between our proposed method, Least square method and Homotopy analysis method is also given and shown via the Table 3 where as the profiles of the residual error are depicted in Figures 4-8. Table and graphs show that efficiency of the proposed method. The error bound and its L2-norm with relevant theorems for mixed interpolation are also given.展开更多
基金supported by the National Science Centre(Grant No.UMO-2013/09/B/ST8/02054)
文摘Research interests have recently been directed towards electrical discharges in multi-phase environments.Natural electrical discharges,such as lightning and coronas,occur in the Earth＇s atmosphere,which is actually a mixture of gaseous phase（air） and suspended solid and liquid particulate matters（PMs）.An example of an anthropogenic gaseous multi-phase environment is the flow of flue gas through electrostatic precipitators（ESPs）,which are generally regarded as a mixture of a post-combustion gas with solid PM and microdroplets suspended in it.Electrical discharges in multi-phase environments,the knowledge of which is scarce,are becoming an attractive research subject,offering a wide variety of possible discharges and multi-phase environments to be studied.This paper is an introduction to electrical discharges in multi-phase environments.It is focused on DC negative coronas and accompanying electrohydrodynamic（EHD） flows in a gaseous two-phase fluid formed by air（a gaseous phase） and solid PM（a solid phase）,run under laboratory conditions.The introduction is based on a review of the relevant literature.Two cases will be considered：the first case is of a gaseous two-phase fluid,initially motionless in a closed chamber before being subjected to a negative corona（with the needle-toplate electrode arrangement）,which afterwards induces an EHD flow in the chamber,and the second,of a gaseous two-phase fluid flowing transversely with respect to the needle-to-plate electrode axis along a chamber with a corona discharge running between the electrodes.This review-based introductory paper should be of interest to theoretical researchers and modellers in the field of negative corona discharges in single-or two-phase fluids,and for engineers who work on designing EHD devices（such as ESPs,EHD pumps,and smoke detectors）.
文摘An electrohydrodynamic （EHD） method, which is based on glow discharge plasma, is presented for flow control in an S-shaped duct. The research subject is an expanding channel with a constant width and a rectangular cross section. An equivalent divergence angle and basic function are introduced to build the three-dimensional model. Subsequently, the plasma physical models are simplified as the effects of electrical body force and work （done by the force） on the fluid near the wall. With the aid of FLUENT software, the source terms of momentum and energy are added to the Navier-Stokes equation. Finally, the original performance of three models （A, B and C） is studied, in which model A demonstrates better performance. Then EHD control based on model A is discussed. The results show that the EHD method is an effective way of reducing flow loss and improving uniformity at the duct exit. The innovation in this study is the assessment of the EHD control effect on the flow in an S-shaped duct. Both the parametric modeling of the S-shaped duct and the simplified models of plasma provide valuable information for future research on aircraft inlet ducts.
基金the National Natural Science Foundation of China (No. 11872241)。
文摘In previous studies, the nonlinear problem of electrohydrodynamic(EHD)ion drag flows in a circular cylindrical conduit has been studied by several authors. However, those studies seldom involve the computation for large physical parameters such as the electrical Hartmann number and the magnitude parameter for the strength of the nonlinearity due to the existence of strong nonlinearity in these extreme cases. To overcome this faultiness, the newly-developed homotopy Coiflets wavelet method is extended to solve this EHD flow problem with strong nonlinearity. The validity and reliability of the proposed technique are verified. Particularly, the highly accurate homotopy-wavelet solution is obtained for extreme large parameters, which seems to be overlooked before.Discussion about the effects of related physical parameters on the axial velocity field is presented.
基金supported by National Natural Science Foundation of China (No.90716025)
文摘Based on the theory of EHD （electronhydrodynamic）, a simplified volume force model is applied to simulation to analyze the traits of plasma flow control in flow field, in which the cold plasma is generated by a DBD （dielectric-barrier-discharge） actuator. With the para- electric action of volume force in electric field, acceleration characteristics of the plasma flow are investigated for different excitation intensities of RF （radio frequency） power for the actuator. Furthermore, the plasma acceleration leads to an asymmetric distribution of flow field, and hence induces the deflection of jet plume, then results in a significant deflection angle of 6.26° thrustvectoring effect. It appears that the plasma flow control technology is a new tentative method for the thrust-vectoring control of a space vehicle.
文摘In this Paper, we have proposed a new weighted residual method known as orthogonal collocation-based on mixed interpolation (OCMI). Mixed interpolation uses the classical polynomial approximation with two correction terms given in the form of sine and cosine function. By these correction terms, we can control the error in the solution. We have applied this approach to a non-linear boundary value problem (BVP) in ODE which governs the electrohydrodynamic flow in a cylindrical conduit. The solution profiles shown in the figures are in good agreement with the work of Paullet (1999) and Ghasemi et al. (2014). Our solution is monotonic decreasing and satisfies , where, α governs the strength of non-linearity and for large values of α solutions are . The residual errors are given in Table 1 and Table 2 which are significantly small. Comparison of residual errors between our proposed method, Least square method and Homotopy analysis method is also given and shown via the Table 3 where as the profiles of the residual error are depicted in Figures 4-8. Table and graphs show that efficiency of the proposed method. The error bound and its L2-norm with relevant theorems for mixed interpolation are also given.
