Transient Response of Straw Filling with Water

In summary, The conversation discusses the phenomenon of water going slightly past the water level in a straw when it is first submerged in water. It is noted that this only happens when the straw is initially capped and then released, and not when the glass is partially filled. The possible explanation given is that the upward momentum of the fluid and the sudden release of pressurized air in the straw contribute to this effect. The effect may also be influenced by the meniscus curve of the water.
  • #1
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Okay, since the most fluids I've studied are from the Euler equation in the context of plasma physics I may be asking a trivial question, but here goes anyway. What I am wondering about is why there is a transient response when I cap a straw with my finger, place the straw in water (while still capped), and then release my finger (while straw fully submerged in water). The water should just fill the straw to the water level, which is what happens in steady-state of course, but I noticed that initially the water in the straw actually goes a bit past the water level of the glass.

I noticed this at a restaurant the other day when I first got my full water glass, and I later noticed when the glass was only 1/3 full, instead of the 7/8 full, that I lost the effect. I couldn't come up with an answer.
 
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  • #2
I've inadvertently noticed that effect as well. All that I can think of is that the upward momentum of the fluid carries it (very temporarily) past the water line. That, in conjunction with the sudden partial vacuum of releasing the previously pressurized air in the straw, might account for it. I don't know what effect the meniscus curve (either regular or reverse) has upon the final appearance.
 
  • #3
I would imagine it's just the fluid's upward momentum. It reaches the equilibrium level with some remaining upward velocity, and therefore continues briefly past.
 

FAQ: Transient Response of Straw Filling with Water

1. What is the transient response of straw filling with water?

The transient response of straw filling with water refers to the behavior of water as it is absorbed by straw. It describes how quickly and how much water is absorbed by the straw, as well as how long it takes for the straw to reach a state of equilibrium with the water.

2. Why is studying the transient response of straw filling with water important?

Studying the transient response of straw filling with water is important for several reasons. Firstly, it helps us understand the process of water absorption in straw, which is important for various industries such as agriculture, packaging, and construction. Additionally, understanding the transient response can also help us design more efficient and effective materials and structures that utilize straw as a filler.

3. What factors can affect the transient response of straw filling with water?

The transient response of straw filling with water can be influenced by various factors, such as the type and quality of the straw, the temperature and humidity of the environment, and the amount of water present. Additionally, the physical properties of the straw, such as its pore size and porosity, can also affect the rate and amount of water absorption.

4. How can the transient response of straw filling with water be measured?

The transient response of straw filling with water can be measured using various techniques, such as gravimetric analysis, where the weight of the straw is recorded over time as it absorbs water. Other methods include using sensors to measure the change in moisture content or using imaging techniques to visualize the water absorption process.

5. Can the transient response of straw filling with water be controlled?

Yes, the transient response of straw filling with water can be controlled through various methods. For example, the rate of water absorption can be slowed down by using a hydrophobic coating on the straw or by adjusting the environmental conditions. Additionally, the amount of water absorbed can also be controlled by varying the physical properties of the straw, such as its density and porosity.

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