# What are weakly and strongly coupled system

• inspike
In summary, the conversation discusses a FEA simulation on Joule heating of a busbar and its thermal expansion. It is suggested to break the study into two separate steps to avoid a weakly coupled system, which involves calculating Joule heating in one step and thermal expansion in the other. The manual states that the Joule heating effect is independent of stresses and strains in the busbar and can be solved using temperature as input for structural analysis. The concept of weakly and strongly coupled systems is briefly mentioned and may refer to the amount and range of interactions between components in the system.

#### inspike

So I am doing a FEA simulation on Joule heating of a busbar and consequently its thermal expansion. So the idea is that if I only use 1 study step, and have the temperature output from the joule heating as an input for thermal expansion, COMSOL calls this as a weakly coupled system, and they don't like it.

Instead, they recommend breaking down the study into 2 steps, the first step to just calculate the joule heating, and the second step just calculate the thermal expansion. The input is still the same.

Personally I feel like nothing mattered, it's just like instead of achieving 1, we choose to do 0.5 + 0.5. I tried both ways, and the answer does not change much from one another. I tried to google the definitions of weakly and strongly coupled systems, and couldn't find any for some reason. So maybe you could explain it to me?

here is the excerpt from the manual I am working from:

"The Joule heating effect is independent of the stresses and strains in the busbar, assuming small deformations and ignoring the effects of electric contact pressure. This means that you can run the simulation using the temperature as input to the structural analysis. In other words, the extended multiphysics problem is weakly coupled. As such, you can solve it in two separate study steps—one for the strongly coupled Joule heating problem and a second one for the structural analysis."

I'm not sure, so don't take my word on it, but I think that it refers to the quantity of information about, and the range of interactions between the components in the system.

## 1. What is a weakly coupled system?

A weakly coupled system is a system in which the interactions between its components are relatively weak. This means that the behavior of one component does not significantly affect the behavior of the other components in the system. Examples of weakly coupled systems include gases and dilute solutions.

## 2. What is a strongly coupled system?

A strongly coupled system is a system in which the interactions between its components are relatively strong. This means that the behavior of one component significantly affects the behavior of the other components in the system. Examples of strongly coupled systems include magnets and dense solutions.

## 3. How do weakly and strongly coupled systems differ?

The main difference between weakly and strongly coupled systems is the strength of the interactions between their components. In weakly coupled systems, the interactions are relatively weak and the behavior of one component has little influence on the others. In strongly coupled systems, the interactions are relatively strong and the behavior of one component has a significant impact on the behavior of the others.

## 4. What are some real-world examples of weakly coupled systems?

Some real-world examples of weakly coupled systems include gases such as air, dilute solutions such as saltwater, and non-interacting particles such as dust particles in the air. These systems have relatively weak interactions between their components and their behavior is not significantly affected by the behavior of other components.

## 5. How can weakly and strongly coupled systems be studied in science?

Scientists can study weakly and strongly coupled systems by using mathematical models and experiments. These approaches allow scientists to observe and measure the behavior of the system and its components, as well as the strength of their interactions. Additionally, scientists can use computer simulations to study these systems and understand how they behave under different conditions.