Measurement of Velocity Induced by a Propagating Arc Magneto-hydrodynamic Plasma Actuator

Experimental and computational studies of a rail plasma actuator (RailPAc) magnetohydrodynamic flow actuator were performed. The actuator functions by inducing flow around a fastmoving gliding arc, with device current ∼ 1000 A, which is generated between flush mounted copper electrodes. Highspeed imaging photometry is used to analyze the composition and internal structure of the arc for flush mounted electrode spacings of 2 mm, 5 mm, and 12.5 mm, as well as freefloating electrodes with 12.5 mm spacing. Results are compared with 2D thermal plasma simulations. The dynamics of the arc movement are found to be dependent on the height of the plasma column above the RailPAc surface and on the presence of prominent anode and cathode jets. Mechanisms are proposed for wallstabilization of the arc and rootjet formation based on agreement between experimental and computational results.

Section: Resultsmentioning

confidence: 99%

Study of the dynamic behavior of the rail plasma actuator arc

Gray

Choi

Sirohi

et al. 2018

“…Their studies on a bench-top RailPAc showed that the Lorentz force can be modeled as the product of the inductance gradient and the square of the arc current. The inductance gradient (0.33 μH m −1 ) of the RailPAc in the test article was obtained from the published value for a similar rail geometry [22]. The peak current I max ∼ 1.3 kA was measured by the current probe.…”

Section: Resultsmentioning

confidence: 99%

“…A magnetohydrodynamic plasma actuator, called the rail plasma actuator (RailPAc) [19][20][21][22], has been developed by the authors to address the drawbacks of DBD plasma actuator concepts and present a lower voltage alternative to the NS-DBD concept that requires very high (∼10 kV) voltage. The absence of moving parts allows this type of actuator to operate with a bandwidth on the order of several ∼kHz.…”

Section: Introductionmentioning

confidence: 99%

“…The arc then accelerates along the rails and imparts momentum to the surrounding air through compression and entrainment effects similar to a moving solid body [14,15]. In previous work, RailPAc prototypes were designed and tested, establishing proof of concept and yielding quantitative measurements of electrical characteristics, impulse imparted to the flow, and induced velocity [19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

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Static stall alleviation using a rail plasma actuator

Choi¹,

Gray²,

Sirohi³

et al. 2018

Self Cite

An experimental study was conducted to investigate the ability of a rail plasma actuator (RailPAc) to alleviate static stall on an airfoil. The RailPAc device consists of parallel rails flush mounted on the upper surface of a VR-12 airfoil, with a high-current (∼1.3 kA) arc bridging the gap between the rails. A Lorentz force (∼0.3 N lasting ∼1 ms) generated on the arc propels it along the airfoil chord and transfers momentum to the surrounding flow. Experiments were conducted in a low speed wind tunnel at two different Reynolds numbers ( and ) and various static angles of attack (up to ∼30°). Particle image velocimetry (PIV) was used to measure the flow over the passive and actuated airfoil, while the airfoil lift was measured using a force balance. The experiments showed that the RailPAc promotes flow reattachment and can suppress static stall over a wide range of angles of attack. Operation of a single RailPAc resulted in ∼40 improvement in post-stall lift and ∼4° increase in stall angle compared to a passive airfoil with an unpowered RailPAc. The results provide insight into the actuation mechanism and demonstrate, for the first time, the ability of the RailPAc to alleviate static stall on an airfoil.

“…Pafford et al [17] measured ∼10 m/s induced velocity in the boundary layer region of an airfoil operating at Re ∼ 450 000. Choi et al [18] expanded upon this work with particle imaging velocimetry on a RailPAc operating in quiescent air to capture the large scale flow disturbance caused by a propagating arc. Their measurements revealed that the moving arc pushes air ahead of its transit through compression, while a high temperature wake region is created behind the transit.…”

Section: Introductionmentioning

confidence: 99%

Effects of anchoring and arc structure on the control authority of a rail plasma actuator

Choi¹,

Gray²,

Sirohi³

et al. 2017

Self Cite

Experiments were conducted on a rail plasma actuator (RailPAc) with different electrode cross sections (rails or rods) to assess methods to improve the actuation authority, defined as the impulse generated for a given electrical input. The arc was characterized with electrical measurements and high-speed images, while impulse measurements quantified the actuation authority. A RailPAc power supply capable of delivering ∼1 kA of current at ∼100 V was connected to rod electrodes (free-floating with circular cross-section) and rail electrodes (flush-mounted in a flat plate with rectangular cross-section). High-speed images show that the rail electrodes cause the arc to anchor itself to the anode electrode and transit in discrete jumps, while rod electrodes permit the arc to transit smoothly without anchoring. The impulse measurements reveal that the anchoring reduces the actuation authority by ∼21% compared to a smooth transit, and the effect of anchoring can be suppressed by reducing the gap between the rails to 2 mm. The study further demonstrates that if a smooth transit is achieved, the control authority can be increased with a larger gap and larger arc current. In conclusion, the actuation authority of a RailPAc can be maximized by carefully choosing a gap width that prevents anchoring. Further study is warranted to increase the RailPAc actuation authority by introducing multiple turns of wires beneath the RailPAc to augment the induced magnetic field.