Rarefaction effects occur only when this quantity is large. For 10 points each:
[10m] Name this quantity that is between 0.1 and ten for transitional flow, and greater than ten for free molecular flow. Second-order expansion of the Boltzmann equation in this parameter gives the ill-posed Burnett equations.
ANSWER: Knudsen (“k’NOOD-sen”) number [accept answers that do not pronounce the “K” in “Knudsen”; prompt on Kn or epsilon]
[10h] Transitional flow can be modeled by the Burnett equation or by a 13-moment equation named for this physicist that is derived via expansion of the Boltzmann equation in Hermite polynomials. With a Soviet, this physicist names a two-dimensional equilibrium equation in ideal MHD.
ANSWER: Harold Grad [accept Grad 13-moment equation or Grad 20-moment equation; accept Grad–Shafranov equation or Grad–Shafranov operator]
[10e] A flow regime named for this behavior occurs at Knudsen numbers between 0.001 and 0.1. At lower Knudsen numbers, a fluid at a boundary is static relative to the boundary, so the “no-[this behavior]” condition applies.
ANSWER: slipping [accept no-slip condition]
<Arya Karthik, Physics>