Discussion Forum

Hello~
I was modeling ionic wind, and I had some problems on it. I selected AC/DC, and PDE module for simulation.
My model is a rectangle 2D domain which represents inner section of pipe. There are two emitting pins, and two grounded plates, which all of them are placed parallel on the pipe's inner walls. I choose AC/DC and PDE modules for simulation. I set emitting electrode as 18kV, and grounded plate as 0kV. Also, I added space charge density, and set its dependent variable as "rho" which coupled with PDE. I used PDE to solve ion transport equation by modifying it as "grad(rho)*grad(V) = rho^2/epsilon, where rho represents space charge density, V stands for voltage, and epsilon is dielectric strength of air." I set the PDE's dependent variable as "rho" which coupled with the AC/DC's space charge density. In PDE, I also set dirichlet boundary condition, which value is calculated by Peek's law, on emitting pin's head.
From the post process of space charge density, I checked the result by observing contour plot. However, always got the same result, that the space charge density was too wide spread across the whole domain. I expected the result of space charge density should be high value near pin, not high value in the whole 2D domain. I already checked the units, and ran with different possible setting in order to acquire ideal result. However, I still can't get it right.
I was also confused with that should I use drift diffusion of plasma module instead of using PDE for ion transport (current continuity)??
Please help me~~ thanks a lot :)