Reynolds number of washing machine like object

In summary: There is no one definitive answer to this question. However, one approach that might be helpful is to run a simulation to see how the flow behaves as the characteristic length is varied. There is no one definitive answer to this question. However, one approach that might be helpful is to run a simulation to see how the flow behaves as the characteristic length is varied.
  • #1
fahraynk
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What would the reynolds number be for a closed pipe spinning like a washing machine? would the characteristic length be the diameter... if so why. Everything I have read is so vauge on this. How can I determine it for strange situations?

Can I skip it and figure out if flow is laminar or turbulent some other way?
 
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  • #2
fahraynk said:
What would the reynolds number be for a closed pipe spinning like a washing machine? would the characteristic length be the diameter... if so why. Everything I have read is so vauge on this. How can I determine it for strange situations?

Can I skip it and figure out if flow is laminar or turbulent some other way?
Depends. Agitator or Spin cycle? Whites, Permanent Press, or Delicates?
 
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Likes boneh3ad
  • #3
The diameter would be one length scale you could pick. It really depends on the physics you hope to study, though. Choosing the length scale for calculating the Reynolds number is all about choosing one that is appropriate to the physics you are trying to describe.
 
  • #4
boneh3ad said:
The diameter would be one length scale you could pick. It really depends on the physics you hope to study, though. Choosing the length scale for calculating the Reynolds number is all about choosing one that is appropriate to the physics you are trying to describe.
Well, sort of like a couette flow with a outer and inner cylinder but just remove the inner cylinder...
What would be the difference in this case between choosing the radius (since the velocity should be 0 in the center?) and choosing the diameter?

I was thinking it would be similar to a couette flow with 2 moving plates going in opposite directions?
Can you recommend something that will help me learn what I should consider when choosing a characteristic length? How did you get the hang of it?

I guess the only reason I need this is to know if I should do a sim in turbulent or laminar flow... I could just try it in both and see. .. but id rather learn how to choose. Plus a simulation could take all day. I tried running a simulation for regular 2d couette flow and once I went over 20 meters/sec the time to solve went up from 10 seconds to 3 hours and growing so fast...
 

FAQ: Reynolds number of washing machine like object

What is the Reynolds number of a washing machine like object?

The Reynolds number of a washing machine like object is a dimensionless number that represents the ratio of inertial forces to viscous forces in the fluid flow inside the machine. It is typically calculated using the object's size, speed, and fluid properties.

Why is the Reynolds number important for a washing machine?

The Reynolds number is important for a washing machine because it helps predict the type of fluid flow inside the machine. This is crucial for determining the efficiency and performance of the machine, as well as potential issues such as turbulence or cavitation.

What is considered a high Reynolds number for a washing machine like object?

A high Reynolds number for a washing machine like object would typically be above 4000. This indicates that the fluid flow inside the machine is turbulent, which can lead to improved mixing and cleaning of clothes. However, extremely high Reynolds numbers can also cause issues such as noise and energy loss.

How does the Reynolds number affect the cleaning ability of a washing machine?

The Reynolds number can affect the cleaning ability of a washing machine by influencing the fluid flow patterns. A higher Reynolds number can result in more turbulent flow, which can help remove dirt and stains more effectively. However, if the Reynolds number is too high, it can also cause damage to delicate fabrics.

Can the Reynolds number of a washing machine be changed?

Yes, the Reynolds number of a washing machine can be changed by adjusting the size, speed, or fluid properties. For example, using a smaller washing machine or reducing the spin speed can result in a lower Reynolds number and smoother fluid flow. However, changing these parameters may also affect the cleaning ability and efficiency of the machine.

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