title: Acceleration statistics as measures of statistical persistence of streamlines in isotropic turbulence.
abstract: We introduce the velocity Vs of stagnation points as a means to characterize and measure statistical persistence of streamlines. Using theoretical arguments, direct numerical simulations (DNS), and kinematic simulations (KS) of three-dimensional isotropic turbulence for different ratios of inner to outer length scales L/eta of the self-similar range, we show that a frame exists where the average Vs = 0 , that the rms values of acceleration, turbulent fluid velocity, and Vs are related by La'/u'2 approximately (V's/u')(L/eta)(2/3+q) , and that V's/u' approximately (L/eta)q with q = -1/3 in Kolmogorov turbulence, q = -1/6 in current DNS, and q = 0 in our KS. The statistical persistence hypothesis is closely related to the Tennekes sweeping hypothesis.
authors.affiliation: Turbulence and Mixing Group, Department of Aeronautics, Imperial College, London, SW7 2AZ, United Kingdom.
authors.forename: S
authors.initials: S
authors.lastname: Goto
authors.forename: D R
authors.initials: DR
authors.lastname: Osborne
authors.forename: J C
authors.initials: JC
authors.lastname: Vassilicos
authors.forename: J D
authors.initials: JD
authors.lastname: Haigh