Changing the trajectory of a projectile can be accomplished by unbalancing the pressure distribution on the body surface and this usually is achieved by surface spreading techniques. The major drawbacks of such techniques are high drag force; fins aerodynamic heating and high time response. To overcome these difficulties, recently application of PLASMA ACTUATORs has been evaluated numerically and experimentally. It is known that the time response of a projectile to control commands is a key factor to its CEP. In the present paper, unsteady flow around a supersonic projectile was calculated using Fluent software and its time response to a control command was analyzed. In this investigation, it is shown that using PLASMA ACTUATOR in comparison with aerodynamic fins can reduce the time response of a projectile about one order of magnitude. This reduction in time response can improve the performance of a projectile significantly.

Recently، active ow control by dielectric barrier discharge (DBD) PLASMA ACTUATORs has been increased. These ACTUATORs are known as more ecient، low-cost، without the need of moving parts، low power consumption، small size، low weight، easy installation and without delay in control. All these features have attracted researcherstousethisACTUATORinavarietyofcases، such as turbulence ow control، laminar to turbulent transition suppression، separation control، drag reduction and mitigationofnoisepollution. However، mostofthestudiessu erfromlackofanaccuratenumericalmodelwhich cansimulatethisphenomenonindetails. Computational analysisofthisphenomenonisverycomplexanddicult due to a combination of ionization phenomena and the interaction of the uid ow with the ACTUATOR e ects. For the exact solution of this phenomenon in certain conditions، Maxwell and Navier-Stokes equations must be combined، while this non-linear solution combination willbeverydicult. Oneofthemodelsformodelingthe interactionbetweentheACTUATORand uid owisanelectrostatic model which adds the ACTUATOR e ect as source termsinthemomentumequationsbysolvingtheelectrical potential equation and charge density equation. In this study، an improvement is proposed to enhance the simulation accuracy of a model used for PLASMA ACTUATOR e ect under interaction with uid ow. In the modied model suggested، a boundary condition for charge distribution on the charged surface is presented based on a relationship between the independent electrical potential and charge density equations. Further، semi-empirical relations are utilized to calculate the produced PLASMA extend. The e ect of the ACTUATOR on induced jet shows a good agreement with experimental results and does not need experimental tests for parametric calibration.

PLASMA ACTUATOR is one of the newest devices in flow control techniques which can delay sepration by inducing external momentum to the boundary layer of the flow. The purpose of this paper, Dynamic stal behavour of a NACA0012 airfoil undergoing pitching motion has been studied by a numerical approach in the present and without PLASMA ACTUATOR. The oscillation frequency and amplitude and the Reynolds number were found to be the major contributors in dynamic stall. The flowfield structure and the associated vortices for this airfoil as well as the impact of the oscillation frequency on aerodynamic efficiency were also studied. The simulations were two dimensinal and the k-ω,SST turbulence model were utilized for the present analysis. The results show that in without PLASMA ACTUATOR increasing the oscillation frequency and amplitude, postpones the dynamic stall to higher angles of attack. Furthermore, as increasing the Reynolds number, both the lift coefficient and the width of the associated hysteresis loop decrease. But when PLASMA ACTUATOR is on, dynamic stall not happen and aerodynamic coefficients improved. The flow field structure revealed that the main cause of the dynamic stall is a series of low pressure vortices formed at the leading edge which shed into downstream and separate from the surface. A secondary vortex will then appear and increases the lift coefficient dramatically. But when PLASMA ACTUATOR is on, sepration is delay and power and size vortex much reduced.

Ahmed body is a standard configuration of road vehicles and most of the studies of automobile aerodynamics are performed based on it. In this paper, the PLASMA ACTUATOR was used as an active flow control method to control the flow around the rear part of the Ahmed body with the rear slant angle of 25° . Experiments were carried out in a wind tunnel at two different velocities of U=10m/s and U=20m/s using steady and unsteady excitations. The hot-wire anemometer was used to measure the vortex shedding frequency at the downstream of the body. Pressure distribution was measured using 52 sensors and total drag force was extracted with a load cell. Furthermore, smoke flow visualization was employed to investigate the flow pattern around the body. The results showed that the PLASMA ACTUATOR was more effective on the pressure distribution and total drag force at the velocity of U=10m/s. In fact, by applying steady and unsteady excitations there was 7. 3% and 5% drag reduction; respectively. While at the velocity of U=20m/s; the ACTUATOR had no significant effect on pressure distribution and total drag. As a remarkable result, the PLASMA ACTUATOR, especially in the steady actuation, has demonstrated its effectiveness on dispersing the longitudinal vortices and suppressing the separated flow on the rear slant at low velocities.

In this paper, boundary layer control technique is investigated on the NREL-5MW offshore baseline wind turbine blade with numerical simulation of linear DBD PLASMA ACTUATOR in a three-dimensional manner. This wind turbine uses pitch control system to adjust its generated power above its rated speed; but below that the controller is inactive. In the current study, operating condition is set such that the control system is off. PLASMA ACTUATOR consists of two electrode and dielectric materials. One of these electrodes is connected with the air and another one is encapsulated with the dielectric material. When the necessary high-level AC voltage is applied to electrodes, electric field forms around the ACTUATOR and an induced wall jet forms with the ionization of the air around the ACTUATOR. Electrostatic model is applied to simulate the effects of PLASMA ACTUATOR and the resulted body force is inserted into flow momentum equations. In the present study, three different control cases are studied. Results show that in all cases, using this ACTUATOR leads to improvement of the velocity profile in controlled section, which influences on pressure distribution and results in rotor torque increment. Finally, increasing in torque leads to growth in produced power of the wind turbine. The highest increment in output power occurs when the ACTUATOR is installed near the root of the blade in the spanwise direction and before low-speed region in the chordwise direction.

In this paper, characteristics of the flow induced in the boundary layer by an AC-Dielectric Barrier Discharge (DBD) PLASMA ACTUATOR are compared against those of a DC-corona wind ACTUATOR. This is achieved by visualization of the induced flow using smoke injection and measuring the horizontal induced velocity. Our measurements show that the maximum induced velocity of an AC-DBD ACTUATOR is about one order of magnitude larger than that of a DC-corona ACTUATOR. For an AC-DBD ACTUATOR, the induced velocity is maximized on the plate surface while for a DC-corona ACTUATOR the induced velocity peaks at about 20mm above the surface. Using flow visualization, we demonstrate that the induced velocity of an AC-DBD ACTUATOR is parallel to the surface, while the induced velocity of a DC-corona ACTUATOR has components perpendicular to surface.

In the last decade, the use of PLASMA ACTUATORs for the application of flow control has been very interested. One of PLASMA ACTUATORs types is the Dielectric Barrier discharge (DBD) PLASMA ACTUATOR. Its properties include simple structure, fast response time, low power consumption and lack of moving parts. In this study, the changes of pressure distribution before and after PLASMA formation at different frequencies and voltages were investigated just above surface at the bottom of the flat plate model and the location of the last PLASMA ACTUATOR. Also the effect of voltage and frequency changes on the pressure distribution has been surveyed. The results of the experimental tests indicate that the PLASMA produces the ionic jet just above surface, in fact, the PLASMA ACTUATORs produce momentum flow in the boundary layer and produce ionic wind. By increasing the voltage and frequency-more than the breakdown voltage-the momentum flow is created in the direction of the PLASMA ACTUATOR. As the voltage increases and the PLASMA becomes visible and vortexes are formed on the flat plate.

In flows with high Reynolds inside the U-shaped tubes, separation phenomenon occurs in the curvature of tubes causing pressure loss and in conditions associated with heat transfer undesirable increase surface temperature in that region is noted. Due to reduced heat transfer rate from surface to fluid temperature increase occurs in industrial applications in addition to reduced heat transfer which causes damage to surface pipes. In the present study, elimination of the separation zone through body force created by PLASMA ACTUATORs and because it reduces the maximum temperature occurred in this region and changes the Peclet number is simulation in this region. For this purpose, the PLASMA ACTUATORs5kV, 12kV and 19kV with square voltage function inside U-shaped tube in the three streams with Reynolds 3000,4500 and 6000 have been placed to influence ACTUATORs on separation control, and maximum temperature occurred at this point be investigated. Calculations using proposed model of Suzen with time-dependent numerical procedure has been done. And results during time performance of 0 to 50 have been reported. The result shows that maximum surface temperature that occurs in the region of separation in the presence of PLASMA ACTUATOR near this region has a significant reduction thatis due to the elimination and change separation region.

One of the important issues in the aviation industry is the Stealth of flying vehicles. One of the stealth methods is to reduce the radar cross section of the target body by means of PLASMA coating and PLASMA absorption properties. DBD PLASMA ACTUATORs are widely used in flow control; however, this experimental study was designed to assess their effect on the level of radar cross section on flat plate in the setting of different voltages and frequencies. PLASMA placement was investigated in two defferent configurations. Results reveal that the number and distance of the PLASMA ACTUATORs as well as their arrangement can influence the radar cross section. The study could eventually achieved 43. 37% (~2/46 dB) reduction in radar cross section using DBD PLASMA ACTUATOR in frequency of 6 KHz and best arrangement.

In this paper, the air flow around a blunt flat plate with a rounded leading edge has been experimentally examined with and without the presence of a PLASMA ACTUATOR. Tests have been conducted with Reynolds numbers ranging from 104 to 105. Significant phenomena in this flow field is the flow separation at the leading edge of the body, which called separation bubble. There are two considerably dimensionless parameters in this experiment. One of them is the leading edge radius ratio to body thickness and other one is the ratio of maximum velocity induced by PLASMA ACTUATOR to free stream velocity. Geometries with the values of R/D=0, 1.16, 2.16, 4.16 were tested. For each geometry, the effectiveness of PLASMA ACTUATOR on the separation bubble is studied in different values of velocity ratio. The results show that, the effect of PLASMA ACTUATOR for the geometry with sharp edge (R/D=0), is negligible, while in geometry with rounded edge, the PLASMA ACTUATOR has significant effect on the separation bubble domain. This effectiveness is enhanced, by increasing of leading edge radius and velocity ratio, so that in rounded edge geometry (R/D=4.16) length of separation bubble is reduced about 75%.