Calculate the damping coefficient of air

So I am trying to calculate the damping coefficient of air passing around a piston that is oscillating in a tube. The idea is completely theoretical. I dont have any real data.

As far as i understand:

1. The viscous sheer stress = mu.du/dy
2. Therefore the viscous sheer force = (piston surface area)*mu.du/dy

But this is not the damping coefficient. How do I calcualte the damping coefficient?

Alex
 

minger

Science Advisor
1,495
1
So long as it's completely theoretical....

You could attach the piston to a spring. In the absence of the air, the spring would oscillate forever given an initial displacement. However, with the air, there will be damping. You could measure the displacement of the spring and use something like the log decrement method to calculate the damping coefficient of the system.
 

jack action

Science Advisor
Insights Author
Gold Member
1,804
1,030
2. Therefore the viscous sheer force = (piston surface area)*mu.du/dy

But this is not the damping coefficient. How do I calcualte the damping coefficient?
The damping coefficient is the ratio of the force over the velocity (F = C * v). So you already have the force, all you need is the velocity of the piston and divide one by the other to get the damping coefficient.
 
The damping coefficient defines the velocity, i want to know the fluid dynamic equations to find the damping coefficient..
 

Related Threads for: Calculate the damping coefficient of air

  • Posted
Replies
3
Views
9K
Replies
2
Views
4K
Replies
1
Views
2K

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving

Hot Threads

Top