No abstract

SUMMARYA theory is developed which describes the adjustment of the flow of a hydrostatically neutral fluid in the lower portion of a fully-turbulent boundary layer, after an abrupt change in surface roughness.The model is based on the hypothesis that the horizontal shear stress is proportional to the turbulent energy. The theory postulates that the flow is primarily governed by the dominant terms of the horizontalmomentum, continuity, and turbulent-energy equations. The model was solved by numerical techniques on a digital computer.Unlike previous models there are no a priori assumptions about the distribution of velocity or stress, the behaviour of the nondimensional wind shear, m k h g length, or momentum-exchange coefficient in the transition region.The theory, in contrast to earlier theories, suggests the distribution of turbulent energy, as well as velocity. An inflection point is predicted in the transition velocity-profile. The nondimensional wind shear is found to differ significantly from unity in the transition region. These predictions agree with observation.

An algebraic fit is made to the results of a numerical analysis describing the collisionless current attracted to cylindrical Langmuir probes whose ratios of probe radius to Debye length are of moderate value. The probe currents indicated by these expressions are compared to some numerically computed values and to values obtained using an approximate analytical solution. This algebraic description of the single-probe response is then used to derive the double-probe characteristics in the region where the current attracted to the probe is potentialdependent. Equations are derived and methods are discussed for accurately determining both electron temperature and number density from these double-probe characteristics. The analogous results for double-probe operation in the region of orbital-motion-limited current collection are also included. NomenclatureA = probe area H = double-probe current 7 = probe current (repelled species) J = probe current (attracted species) j = normalized current (attracted species) Jo = Eq. (2) Jc = Boltzmann's constant L = probe length M = mass N = density q = one electronic charge r = probe radius T = temperature V = applied probe-to-probe or probe-to-reference potential Z = number of electron charges on particle a = Eq. (5) ft = Eq. (6) e = Eq. (21) 6 = kT/Zq effective temperature (eV) X = (kT/4:TrNZ 2 q 2 ) 112 Debye length T = -|ln(M + /M_) = potential measured with respect to the plasma potential X = <|>/0_ nondimensional potential = V/0-nondimensional applied potential Subscripts a,r = attracted, repelled e,i = electron, ion +,-= colder, hotter 1,2 = numerical designation for double-probes / = open circuit (floating) potential

No abstract