Reece Roth describes in his paper "FLOW RE-ATTACHMENT AND ACCELERATION BY PARAELECTRIC AND PERISTALTIC ELECTROHYDRODYNAMIC (EHD) EFFECTS" the peristaltic effect with which a very fast ionic wind can be generated near the surface. He talks about 100 m/s and more!
1. Has somebody measured velocities over 20 m/s?
2. I know he was sent to jail after violating technology export controls.
(https://projectalpha.eu/john-reece-roth-and-export-control/)
Does this mean the USAF is also doing research in the field of the peristaltic plasma effect and didn't want the Chinese to compete with them?
Dear Matthias,
I think you might be interested in plasma actuators more generally. They are a huge topic today. You can look for DBD actuators (either nanosecond pulsed or AC DBD), corona discharge actuators, sliding discharge actuators,... You can look at the work of different groups (first names that pops into my mind: J. Kriegseis, E. Moreau, J. Pons, T.E. McLaughlin and I am already skipping lots of people here). The main issue is that, even if the ion wind is of several hundred of m/s, the momentum transfer to the free-stream is weaker in amplitude, but much thicker (the plasma itself
Dear Sylvain Grosse ,
thanks for the answer. I'm familiar with the literature you recommended.
The problem is that for most aerodynamic applications the generated ionic wind velocity is too low to have an impact on, for example, an aircraft wing at travel speed.
Maybe you are familiar with plasma actuators in the smoke channel like it is shown here:
https://www.youtube.com/watch?v=mVJjn1pt08g
The effect is huge but the larger the velocity difference between the travel speed and the ionic wind the smaller the effect.
Therefore, enhancing the ionic wind velocities should generate a greater impact on the boundary layer separation of the aircraft wing.
But as far as I know, nobody has measured such high velocities of the ionic wind despite there are more and more publications...
Dear Matthias Lindner
It is true. For now, plasma actuators are mostly limited to low Reynolds number applications when they are used with a standard AC signal. The problem is that even if the charged particles reach a high velocity, not all the momentum is transfered to the free airflow. If you think about it, the ions will also have less momentum to transfer to a neutral particle when this particle already has some momentum in the same direction.
However, nanosecond pulse actuators show interesting results over a range of airspeed (e.g. Zhang et al. AIAA 2015-2955 or Coumar et al. Exp. Fluids 58:74). They however generate a flow using thermal properties.
The problem with the AC discharge is that is reaches its peak performance when the plasma becomes a filamentary discharge. Managing the right power input is also important. It is not rare (in my experience) that an AC DBD performs well with a nice homogeneous discharge for some time, but breaks at some point (aging of the material ?). The higher the power consumption, the more critical having a perfectly homogeneous dielectric and a smooth air electrode (at a microscopic level) are so that the plasma does not change its properties.
Typically, the AC DBDs are bit better when using more "fancy" geometries such as serpentine electrodes or serated electrodes, or when placed in a vortex-generator configuration rather than using a co-flow configuration, but these aapplications re still limited. to low speeds
Are you sure this is the correct account Jacinto Jesús Rodríguez Pérez
? I had a look but everything is in Spanish and a simple search did not give any indication of mentionning the work of Prof Roth. Since my access to the website is limited (I do not have an account so can only see the front main articles). I am researching in plasma actuation, so I am very curious about the explanation. Mind giving a hint in the answers here ?
Dear Matthias Lindner ,
I just realised I forgot to talk about another important point brought by Prof Roth. In his work, he also mentions the possibility of creating a travelling wave of plasma by trapping it in a moving electric field. Until now, you would be able to find past papers about DBD arrays (I can send the citations I have if you want). Their limitation is that they do not fully work in the same way (they simply put DBDs one behind the other). If I have understood the idea of Prof Roth, the goal is to form the plasma, and through an array, actuate each stage in a sequence to force the plasma (or a pocket of plasma) to travel at a particular speed with something as simple as a moving electric field in the downstream. The few papers where a try was made did not see the expected effect. The main limitation is the sequencing. Not only, optimising the delays between the stages, but also with the equipment. It can be hard to find reliable relays for high voltage, with a fast enough response (and that are small and light enough for air operation). Prof Roth project was with USAF which might give good funding and more cooperation for such project that could not only make your aircraft more efficient and less noisy, but also more stealthy by absorbing certain EM wave lengths in the plasma. However, the idea of a travelling plasma wave is very interesting. As we see the development in the HV equipment, more advanced plasma actuation might be possible in the future. I hope this is filling the gap I left in my last answer.
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