Calculating Shaft Natural Frequency in Free Air and Liquid

In summary, the conversation discusses the calculation of natural frequency of shafts in tanks. While many literature sources focus on calculating it in free air, only one book mentions considering the damping effect of the liquid. The question is raised about the best method for calculation - in free air or in liquid. The response suggests that if the mixer shaft may be operated without or with low liquid in the tank, it should be calculated for air.
  • #1
Christoffer28
2
0
Hello Fellow members.

In many litterature about mixing liquids in tanks, they describe how to calculate the natural frequency of shafts in free air.
But i have only found one book that describe about natural frequency of shafts in liquid, and it should have a damping effect of the natural frequency.

The question is: What is the best method? to calculate the frequency in free air or in liquid?Thanks in advance.
Christoffer
 
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  • #2
Welcome to PF.

Christoffer28 said:
What is the best method? to calculate the frequency in free air or in liquid?
If the mixer shaft might be operated, even only once, while there is no, or low, liquid in the tank, then it must be calculated for air.
 
  • #3
Ok, so its a question of dimensioning a worst case scenario.

Thanks for the answer :)
 

Related to Calculating Shaft Natural Frequency in Free Air and Liquid

1. What is the purpose of calculating shaft natural frequency in free air and liquid?

The purpose of calculating shaft natural frequency in free air and liquid is to determine the resonance frequency of a rotating shaft. This is important because if the rotating speed of the shaft is close to its natural frequency, it can cause severe vibrations and potentially damage the equipment.

2. How is shaft natural frequency in free air and liquid calculated?

The shaft natural frequency in free air and liquid is calculated using the equation: f = (1/2π) * √(k/m), where f is the natural frequency, k is the stiffness of the shaft, and m is the mass of the shaft.

3. What factors can affect the shaft natural frequency in free air and liquid?

There are several factors that can affect the shaft natural frequency, including the material and shape of the shaft, the rotational speed, and the surrounding fluid medium. Changes in any of these factors can alter the stiffness and mass of the shaft, thus impacting its natural frequency.

4. How does the natural frequency in free air differ from that in liquid?

The natural frequency of a shaft in free air is typically higher than that in liquid. This is because the stiffness of the shaft is affected by the surrounding medium, and liquids are typically less stiff than air. Additionally, the added mass of the liquid can lower the natural frequency of the shaft.

5. What are the potential consequences of not calculating the shaft natural frequency in free air and liquid?

If the shaft natural frequency is not calculated and taken into consideration, it can result in excessive vibrations and potential damage to the equipment. This can lead to increased maintenance costs, downtime, and potentially unsafe working conditions.

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