Solving Distance of Starch Particles in Fluid w/Stoke's Law

In summary, the conversation discusses an experiment to separate different sizes of starch particles using a long cylinder and fluid outlets for each size. The Stokes' law is used to estimate the time for particles of certain sizes to fall to the bottom of the cylinder, but there is a question about how to calculate the distance and time for 90% of 10µm particles to reach the bottom. Other relevant equations are considered, such as the sedimentation equation and the equation for gravity settling of cassava starch in water.
  • #1
nabilah
1
0
1. Homework Statement
I did an experiment to separate different sizes of starch particles (range of size 1 µm to 10 µm). I mixed the starch powder with water in a long cylinder. I have to create model by using long cylinder to separate those starch particles according to their size (<1µm, <5µm.,<10 µm) with fluid outlet for each sizes.

I use the Stoke's law to estimate the time of starch particle (for example for size 5 µm) left on top of the solution. but I have a problem on how to calculate/estimate the distance of 90% of 10µm starch particles in fluid (water) reach to the bottom of cylinder? and estimation of time for it to fall at the bottom. I figured out that I can use a Stoke's law but this equation could not use to estimate for how distance for 90% of 10 micrometer of starch particles reached the bottom of the cylinder.
stokes_law_terminal_velocity.png
2. Relevant
equations

By using the stoke's law I can estimate the time for <5 µm of starch particle left on the top.
stokes_law_terminal_velocity.png




The Attempt at a Solution



Can I use the other relevant equation other than Stle's law to measure the distance of 90% 10µm starch travel until reach the bottom of cylinder?
I tried to use the equation

d=Vi(t)+(0.5*a*t2)
but I think this equation is not relevant to my case.
[/B]
 
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  • #2
https://en.wikipedia.org/wiki/Sedimentation

http://www.nzifst.org.nz/unitoperations/mechseparation3.htm

https://www.researchgate.net/publication/229128063_PH-Postharvest_Technology_Kinetics_of_Gravity_Settling_of_Cassava_Starch_in_its_Aqueous_Suspension
 
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  • #3
You could start with a very simple model which assumes that the particles all fall separately from each other and that the particles reach terminal velocity almost immediately on entering the water .
 

1. What is Stoke's Law?

Stoke's Law is an equation that describes the settling velocity of small particles in a fluid. It is used to calculate the distance that particles, such as starch particles, will travel in a fluid based on their size, density, and the viscosity of the fluid.

2. How is Stoke's Law used to solve for the distance of starch particles in a fluid?

To solve for the distance of starch particles in a fluid, we use the equation: D = [2/9)(g-ρf)/η]r^2, where D is the distance traveled, g is the gravitational constant, ρf is the density of the fluid, η is the viscosity of the fluid, and r is the radius of the starch particles. By plugging in these values, we can solve for the distance the particles will travel in the fluid.

3. What factors affect the distance starch particles will travel in a fluid according to Stoke's Law?

The distance that starch particles will travel in a fluid according to Stoke's Law is affected by the size and density of the particles, the viscosity of the fluid, and the force of gravity. The larger the particles, the faster they will settle, while the denser the particles, the slower they will settle. Additionally, the more viscous the fluid, the slower the particles will travel, and the stronger the force of gravity, the faster the particles will settle.

4. How is the distance of starch particles in a fluid measured using Stoke's Law?

The distance of starch particles in a fluid can be measured using a variety of methods, depending on the specific experiment. One common method is to observe the particles settling in a graduated cylinder and measuring the distance they travel over a set period of time. Another method is to use a device called a viscometer, which measures the viscosity of a fluid and can then be used to calculate the distance the particles will travel using Stoke's Law.

5. What are the practical applications of understanding Stoke's Law for solving the distance of starch particles in a fluid?

Understanding Stoke's Law and its application to solving the distance of starch particles in a fluid has many practical applications. It can be used in industries such as food processing, where it is important to understand how particles will settle in different fluids, or in environmental science, where it can be used to study sedimentation in bodies of water. It is also useful in medical research, where it can be used to study the behavior of cells and other particles in various fluids in the body.

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