Flow induced vibration of a mobile cylinder

In summary: Expert SummarizerIn summary, to solve the fluid structure interaction case of a flexible cylinder with a flow of air and cross flow of water, the equation of motion (ma+cv+kx=f) can be used, with the natural frequency of the air (f = (1/2π)√(k/m)) as input. The effects of fluid added mass can be considered by calculating the added mass coefficient and incorporating it into the equation of motion. Further clarification and hints can be provided if needed.
  • #1
hoomanya
90
0
Hi,
I am working on a case with a flexible cylinder with a flow of air inside and a cross flow of water. This is a fluid structure interaction case and the case is such that I can define the natural frequency of the air inside the cylinder and that would then be used to solve the structure equation (ma+cv+kx=f). I am meant to change the inlet velocity of water and investigate the damping ratio and frequency of the vibrating cylinder.
I am confused as how to evaluate the frequency of the vibrating cylinder cylinder, which equations can I use to evaluate this frequency? Would that need to be evaluated using using the fluid added mas effects, etc.
I would appreciate any hints if you have come across a similar case.
Thanks,
H
 
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  • #2


Hello H,

Thank you for reaching out and sharing your case with us. It sounds like you are working on a very interesting fluid structure interaction problem. To evaluate the frequency of the vibrating cylinder, you can use the equation you mentioned (ma+cv+kx=f) which is commonly known as the equation of motion. In this equation, m represents the mass of the cylinder, a represents its acceleration, c represents the damping coefficient, k represents the stiffness of the structure, and x represents the displacement of the cylinder.

To solve this equation, you will need to use the natural frequency of the air inside the cylinder, which can be calculated using the equation f = (1/2π)√(k/m). This frequency will be used as the input in the equation of motion to determine the displacement and acceleration of the cylinder at different inlet velocities of water.

In order to consider the effects of fluid added mass, you can use the added mass coefficient, which is a dimensionless parameter that represents the ratio of added mass to the mass of the fluid displaced by the vibrating cylinder. This coefficient can be calculated using various methods, such as empirical formulas or numerical simulations. Once you have the added mass coefficient, you can incorporate it into the equation of motion to obtain a more accurate solution for the frequency and damping ratio of the vibrating cylinder.

I hope this helps you in your case. If you have any further questions or need more clarification, please do not hesitate to ask. Best of luck with your research.
 

1. What is flow induced vibration of a mobile cylinder?

Flow induced vibration of a mobile cylinder is a phenomenon that occurs when a cylinder is placed in a fluid flow and experiences oscillations or vibrations due to the forces exerted by the fluid. This can lead to potential damage or failure of the cylinder if not properly managed.

2. What factors influence flow induced vibration of a mobile cylinder?

The main factors that influence flow induced vibration of a mobile cylinder are the fluid flow velocity, the size and shape of the cylinder, and the properties of the fluid, such as density and viscosity. Other factors that can play a role include the surface roughness of the cylinder and the presence of any nearby structures or obstacles.

3. How can flow induced vibration of a mobile cylinder be mitigated?

There are several methods that can be used to mitigate flow induced vibration of a mobile cylinder. These include adding damping devices, modifying the shape of the cylinder, and adjusting the fluid flow velocity. Other techniques such as using coatings or altering the geometry of the surrounding structures can also be effective.

4. What are the potential consequences of flow induced vibration of a mobile cylinder?

The consequences of flow induced vibration of a mobile cylinder can range from minor structural damage to catastrophic failure. The vibrations can cause fatigue and stress on the cylinder, leading to cracks and fractures. In extreme cases, this can result in complete failure of the cylinder, potentially causing harm to nearby structures or people.

5. What are some real-world applications of flow induced vibration of a mobile cylinder?

Flow induced vibration of a mobile cylinder is a common issue in various industries, including oil and gas, marine, and aerospace. It can affect structures such as pipelines, offshore platforms, and aircraft wings. Understanding and managing this phenomenon is crucial to ensuring the safety and reliability of these structures.

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