# Questions tagged [diffusion]

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### Momentum Diffusivity without Mass Diffusion in Liquids

I have been reading about the differences between momentum and mass diffusivity. I understand that mass diffusion occurs because of the "random walk" of individual molecules which over time ...
• 145
41 views

### Diffusor for uniform illumination

I have an LED with a beam angle of 120° and I need to illuminate an area in the shape of a circle with a radius of 3.5 mm. My objectives are as follows: Achieve a uniform illumination of the circle (...
• 101
1 vote
354 views

### Errors obtained in the numerical solution of the 1D convection-diffusion equation

I have been trying to solve the 1D convection-diffusion equation In implementing the above, I have tried to follow closely the method described here: https://uk.mathworks.com/support/search.html/...
• 23
1 vote
2k views

### Analytical solution for the 1D convection-diffusion equation

The Ogata and Banks analytical solution of the convection-diffusion equation for a continuous source of infinite duration and a 1D domain: where C [mol/L] is the ...
• 23
1 vote
57 views

### Will pressurizing container slow moisture permeation?

I have some electronics housed inside a sealed plastic enclosure, which will be used in a very humid environment. The environment can be assumed to be 100% humidity at a constant temperature, all the ...
• 11
110 views

### Is the silicone oil used in a diffusion pump oil special?

I have obtained two diffusion pump stages from a pair of very old Vacuubrand high vacuum pump. The rotary vane pump in one of them was dead and another overheating. So, I salvaged only the diffusion ...
1 vote
105 views

### How the 3M Aura 9332+ masks filtrate airborne particles/virus?

The 3M Aura 9332+ mask is labeled FFP3 which means that it filters at least 99% of airborne particles. This article mentions that N95 masks (which filtrate 95% of airborne particles) filtrate the ...
• 175
1 vote
47 views

### P-N junction depletion region

Before I explain my problem I'd like to mention I'm still green and about 2 weeks into these topics. I learned most of it from youtube videos, wikipedia and other science sites, so I'll be explaining ...
246 views

### What is the difference between a diffuser and a duct in turbines?

I have been reading this paper, which addresses the advantages of diffusers in cross flow turbines. The abstract says (emphasis is mine): A CP’s extraordinary improving resulted when yaw increased ...
1 vote
47 views

### Diffusion of miscible fluids

I was trying to model experimentally the interdiffusion of two miscible liquids. Is there an optical method to find out the extent of diffusion; the addition of fluorescing agent into any of the two ...
43 views

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### Waterproof Case Time Limits

Some cell phone cases have a waterproof rating of IP-68, often specifying that they can tolerate immersion to 6 feet for 30 minutes or 3 feet for 60 minutes. My understanding, however, is that a good ...
• 211
Imagine the following initial condition: Two completely miscible fluids A and B with different dynamic viscosities $\eta_A$ and $\eta_B$ are seperated in a container with fixed Volume $V_0$ and ...