How do airplanes fly? And for that matter, how do sharks swim through water? Both are massive objects with interesting shapes moving through a fluid (both air and water are fluids.)
After all this time you’d think that we know all the details of how an airplane flies. There must be some specific and agreed-upon explanation. Air hits a plane, air and plane then follow laws of physics, and voilà, the plane flies, right?
Although flight indeed is in accord with the laws of physics, the specific ideas about how this happens are incomplete and controversial.
What’s the controversy about? What new ideas are being proposed?
Bernoulli theorem idea
(Here the class will look into the general idea.)
image from http://www.thaitechnics.com
This explanation is from the Scientific American article.
Newton’s laws of motion
(Here the class will look into the general idea.)
This explanation is from the Scientific American article.
New Theories of lift
These ideas are also from the Scientific American article.
How do fish fly through water?
Just as aerodynamics explains how airplanes generate lift and fly through the air. hydrodynamics explains how fish generate lift and fly through water.
And yes, fish do fly through water. If they stop moving, then they literally fall down to the bottom of the ocean.
We all know how interesting hammerhead sharks are. Why do their heads have this peculiar shape?
Part of it has to do with the fact that their head is a giant electromagnetic sensor; it can detect the EM fields of nearby prey. But evolution optimizes body design in more than one way. Sharks need to do more than sense prey, they need to move efficiently.
This recent paper, A hydrodynamics assessment of the hammerhead shark cephalofoil, shows that the shape of their head may increase maneuverability as well as produce dynamic lift similar to a cambered airplane wing.
See Gaylord, M.K., Blades, E.L. & Parsons, G.R. A hydrodynamics assessment of the hammerhead shark cephalofoil. Scientific Reports 10, 14495 (2020). https://doi.org/10.1038/s41598-020-71472-2
Also see : Pioneers of flight, How do airplanes fly?, the graveyard spiral, and breaking the sound barrier – Flight
References
No One Can Explain Why Planes Stay in the Air: Do recent explanations solve the mysteries of aerodynamic lift? By Ed Regis
Scientific American, February 2020, Volume 322, Issue 2
Aerodynamic Lift, Part 1: The Science, Doug McLean, The Physics Teacher Vol. 56, issue 8, 516 (2018)
https://doi.org/10.1119/1.5064558
Aerodynamic Lift, Part 2: A Comprehensive Physical Explanation, Doug McLean, The Physics Teacher Vol. 56, 521 (2018)
https://doi.org/10.1119/1.5064559
Understanding Aerodynamics: Arguing from the Real Physics, Doug McLean. Wiley, 2012
You Will Never Understand Lift. Peter Garrison, Flying; June 4, 2012.
Flight Vehicle Aerodynamics. Mark Drela, MIT Press, 2014.
#Flight #aerodynamics #Bernoulli #Lift
Learning Standards
2016 Massachusetts Science and Technology/Engineering Curriculum Framework
HS-PS2-1. Analyze data to support the claim that Newton’s second law of motion is a mathematical model describing change in motion (the acceleration) of objects when acted on by a net force.
A FRAMEWORK FOR K-12 SCIENCE EDUCATION: Practices, Crosscutting Concepts, and Core Ideas
PS2.A: FORCES AND MOTION
How can one predict an object’s continued motion, changes in motion, or stability?
Interactions of an object with another object can be explained and predicted using the concept of forces, which can cause a change in motion of one or both of the interacting objects… At the macroscale, the motion of an object subject to forces is governed by Newton’s second law of motion… An understanding of the forces between objects is important for describing how their motions change, as well as for predicting stability or instability in systems at any scale.
NGSS
2016 High School Technology/Engineering
HS-ETS1-2. Break a complex real-world problem into smaller, more manageable problems that each can be solved using scientific and engineering principles.
HS-ETS1-4. Use a computer simulation to model the impact of a proposed solution to a complex real-world problem that has numerous criteria and constraints on the interactions within and between systems relevant to the problem.
College Board Standards for College Success: Science
PS-PE.1.2.2 Analyze force diagrams to determine if they accurately represent different real-world situations.
PS-PE.1.2.4 Given real-world situations involving contact, gravitational, magnetic or electric charge forces and an identified object of interest:
PS-PE.1.2.4a Identify the objects involved in the interaction, and identify the pattern of motion (no motion, moving with a constant speed, speeding up, slowing down or changing [reversing] direction of motion) for each object.
PS-PE.1.2.4b Make a claim about the types of interactions involved in the various situations. Justification is based on the defining characteristics of each type of interaction.PS-PE.1.2.4c Represent the forces acting on the object of interest by drawing a force diagram.
PS-PE.1.2.4d Explain the observed motion of the object. Justification is based on the forces acting on the object.
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