Experimental study on both ionic wind and resuspension of particles under unequal electrostatic field

Ionic wind and resuspension of particles under an unequal electrostatic field have been investigated experimentally using a needle electrode and grounded plate where fine particles are deposited. As voltage is applied to the needle electrode, a straight stream is immediately generated around the needle. Then the straight stream induces a new flow around it. When the straight stream impacts on the target, circulated flow is generated and grows gradually with time. Finally, an almost steady jet stream is formed. Ionic current from the needle to the target increases with almost the square of the electrostatic field between the needle and particle layer. If the strength of the electrostatic field is high enough, most of particles are resuspended from the layer immediately after the voltage is applied to the needle. However, if the strength is reduced, some heaps remain on the layer. Resuspension of particles occurred in two stages. The more the initial mass of the layer, the faster the resuspension velocity of particles in the first stage. The velocity increases almost linearly with the electrostatic field. The fact suggests that the velocity in the first stage is related to the theoretical maximum velocity of the ionic wind.