Offensive%20Heat%20Transfer%20in%20the%20Middle%20Ages

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Offensive Heat Transfer in the Middle Ages

• Brady Aydelotte
• Spencer Harding

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Pre-launch Assumptions

• The surface of the arrow had sufficient time to
  come to the adiabatic flame temperature of the
  residual fuel oil
• The surface of the arrow was burned away, leaving
  only a uniform coating of carbon
• Modern compound bows have arrow speeds of
  approximately 100 m/s for 65lbs of draw weight.
  Medieval compound bows had draw weights in excess
  of 120lbs. We assumed a velocity of 100 m/s for
  our arrow.

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In-flight Assumptions

• Time 3.5 seconds
• Distance 250 meters
• X-Velocity 71m/s

Assume spherical tip

• Arrow velocity is much greater than flame
  velocity so the flame on the arrow goes out
  immediately
• The effect of radiation and convection were
  combined into a convective coefficient
• The Whitaker correlation (eq 7.56) for spheres is
  still valid for Re above 8e4

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Equations
Radiation
Convection
Lumped Capacitance
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Results
Tf 1070 K
The final temperature, 1070 K is much greater
than the ignition temperatures of wood and straw
(610 and 580 K respectively) common building
materials of the day.
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Conclusion

• Medieval flaming arrows would be capable of
  igniting wooden and straw thatched structures
  even when the flame on the end went out.

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References

• Flame Structure and Processes, R.M. Fristrom,
  Oxford university Press, 1995
• http//www.engineeringtoolbox.com/fuels-ignition-t
  emperatures-d_171.html
• http//www.sciencedirect.com/science?_obArticleUR
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  f4b7051f3489c022f65c4
• http//www.economy-point.org/i/ignition-temperatur
  e.html
• The Great Warbow From Hastings to the Mary Rose
  (Hardcover). Matthew Strickland. Sutton
  Publishing 2005. ISBN-10 0750931671, ISBN-13
  978-0750931670
• Fuels and Engines Technology, Energy,
  Environment  By Jean-Claude Guibet, Emmanuelle
  Faure-Birchem