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Recent content by ChrisGreaves

  1. C

    Energy cost of air displacement?

    rb, thank you for this response. I agree that my assumptions are simplistic. My thinking started while driving a car on a highway, and were formed as a mental exercise to get what is sometimes called a first approximation to energy requirements. Back then I thought to get a "worst-case value"...
  2. C

    Energy cost of air displacement?

    Hello mintjulep. I will try using the drag co-efficient, which is probably a perfect fluid engineering solution to the cost of moving a car through air. I will have to think about this. I was trying to develop the image of a solid rectangular block ("car") pushing air upwards. In practice I...
  3. C

    Energy cost of air displacement?

    Hi Dave. I wasn't assuming that a total vacuum was established at all. I know from experience that air is pushed out of the way and flows around the car. The car isn't a piston in a (rigid?) tube; the car is a particle immersed in a fluid medium (air) If I watch a goldfish immersed in water...
  4. C

    Energy cost of air displacement?

    Hi Greg. I understand this. But I was considering the energy required to displace (say) a linear foot of air, displaced as the car moved forward one foot along the roadway. That air must be displaced, sideways, or upwards, or below the car. We know, do we not, that air resistance consumed...
  5. C

    Energy cost of air displacement?

    I apologize for my delay in getting back to this topic. Ed, my basic physics classes in high school said that while the kinetic energy of a particle is given by 1/2 m v^2, the kinetic energy of a fluid is 1/2 m v^3. That is, for air, water etc, we need to use the cube of the velocity (since the...
  6. C

    Energy cost of air displacement?

    New here. Aeronautics because I am curious about the cost of airflow around an object. In my case a Toyota Rav4 driving down the highway; calm weather, dry etc. Just the Rav 4. I first proposed this discussion on Eileen's Lounge, but a user suggested I check out at this site. The Rav4 is five...
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