Changing/Controling relative permeability

In summary, the conversation discusses the use of metamaterials and their overwhelming complexity, specifically regarding negative permeabilities. One way to control the relative permeability of a material is by creating a resonant structure that causes the imaginary part to peak and the real part to change sign. This can be achieved by exciting surface plasmons in nanoparticles or building a unit cell with resonant behavior. In order to achieve the desired behavior, distributed effects must be used and periodic structures are commonly utilized.
  • #1
jupiter13
12
0
Hey everyone,

I've been looking at metamaterials, and it's quite an overwhelming subtopic to be introduced to. Most of the stuff I'm finding has to do with negative permeabilities. I'm wondering how exactly we control what relative permeability a material has and how fine that control is, not just so that its a negative value, but that it's any value other than what you'd measure if you found it in nature?
 
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  • #2
The most common is to create a resonant structure such that the permeability and permittivity resonate like in a plasma. If you recall, the resonanct behavior causes the imaginary part to peak and the real part to change sign. By controlling the resonances, we can get both the permeability and permittivity to be negative at the same time in addition to hopefully have a small amount of loss. Such resonances can be done naturally by exciting surface plasmons in nanoparticles. If we permeate a material with nanoparticles and excite a surface plasmon on the particles, then the bulk effect is like there is a plasma behavior throughout the material itself. Or we can build a unit cell that exhibits resonant behavior (like an L-C circuit) and build up a material off of these unit cells.

In the end, what we have to do is use distributed effects to get the behavior that we want. So must of the time you will be dealing with periodic structures.
 

1. What is relative permeability?

Relative permeability is a measure of how easily a fluid can flow through a porous medium, such as rocks or soil. It is expressed as a fraction or percentage of the maximum possible flow rate through the medium.

2. How does changing relative permeability affect fluid flow?

Changing relative permeability can significantly impact fluid flow through a porous medium. If the relative permeability increases, the fluid can flow more easily, resulting in a higher flow rate. On the other hand, decreasing relative permeability can restrict fluid flow and decrease the flow rate.

3. What factors can influence relative permeability?

Relative permeability can be influenced by several factors, including the type and properties of the fluid, the characteristics of the porous medium, such as pore size and connectivity, and the presence of any barriers or obstructions.

4. Can relative permeability be controlled?

Yes, relative permeability can be controlled through various methods, such as altering the properties of the fluid or the porous medium, applying external pressure or temperature changes, or using chemical treatments to modify the pore structure of the medium.

5. How is relative permeability measured?

Relative permeability is typically measured in a laboratory setting using specialized equipment, such as a permeameter or core flooding apparatus. These instruments simulate the conditions of a porous medium and measure the flow rate of different fluids to determine their relative permeability values.

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