How Does DDWFTTW Work and What Are Its Key Principles?

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  • Thread starter Thread starter Opus_723
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SUMMARY

The discussion centers on the principles of Directly Downwind Faster Than The Wind (DDWFTTW) vehicles, specifically how they can achieve speeds exceeding wind speed. Key insights include the role of the propeller, which generates thrust by slowing down the wind relative to the ground, and the effective gearing between the wheels and the propeller that allows for increased force despite power losses. The conversation highlights the importance of distinguishing between true wind and relative wind, as well as the mechanics of how these vehicles operate at varying speeds, including the transition from windmill mode to thrust generation.

PREREQUISITES
  • Understanding of aerodynamic principles and forces
  • Familiarity with propeller mechanics and pitch variations
  • Knowledge of relative versus true wind dynamics
  • Basic concepts of energy transfer and efficiency in mechanical systems
NEXT STEPS
  • Research the mechanics of propeller pitch and its impact on thrust generation
  • Explore the physics of wind dynamics and relative motion
  • Study the design and performance of DDWFTTW vehicles, including the Blackbird cart
  • Investigate the principles of energy conversion in mechanical systems
USEFUL FOR

Engineers, physicists, and enthusiasts interested in advanced vehicle dynamics, aerodynamics, and renewable energy applications will benefit from this discussion.

  • #271
rcgldr said:
In articles about vehicle dynamics (try a web search for "vehicle dynamics contact patch"), contact patch is often used as a dynamic term, and in this context, the contact patch moves with the vehicle (it has the same velocity wrt ground). There are also statements made about how the tread surface in a tire deforms as it flows through the contact patch, yet another dynamic usage of the term contact patch.
OK, that makes the terminology confusing, but that happens sometimes. The important velocity for determining work is the velocity of the material in the contact patch (which is equal to the velocity of the ground assuming rolling without slipping), not the velocity of the "vehicle dynamics contact patch" (which is equal to the velocity of the vehicle under standard assumptions).
rcgldr said:
the static friction force between tire and road can perform work
Yes, in a frame where the ground is moving.
 
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  • #272
I think that it is time to close the thread permanently. I tried to keep it open to support our good members, but it seems to be full of physics misunderstandings which I think are too muddled now to continue.
 
Last edited:

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