Part 2 for real
Updated: 10/23/2020
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Storyboard Text

• What causes wind?
• Oh, a difference in pressure!
• Viscosity alone can’t account for the water being pulled into the blaster. Think about other properties that can make fluids move.
• The combined pressure and viscous forces make up the molecular stress considerations for the fluid motion.
• Yes! This difference is created because the water being pulled in is affected by atmospheric pressure while the pressure inside the tube is created by expanding the capacity.
• This causes water to flow up the tube to relieve the pressure difference.
• Have you heard of momentum before?
• Because there is a pressure change in a contained system, there is also a change in velocity that must be considered.
• This term to consider is called the bulk flow.
• To evaluate it within the volume, we calculate momentum per volume.
• It’s basically how much motion an object has and is mathematically defined by mass times velocity.
• No, what’s that?
• Bulk flow is evaluated both in the direction of the fluid as well as perpendicular to the flow. Yes, that’s density!
• Do you know what mass per volume is?
• So, if the flow is turbulent, then the flow is moving in multiple directions, right?
• Yes, that’s density!
• Depending on how fast the pump is pulled on the water blaster there may or may not be bulk flow to be considered.
• Yes! And when the flow is laminar then it can be assumed to only be flowing in one direction.
• Okay! I think I understand now. Thank you both so much!