高シュミット数物質噴流拡散場における物質フラックスの統計的特性(流体工学,流体機械)

概要

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Statistical characteristics of mass flux in an axisymmetric turbulent jet diffusion field of a high-Schmidt-number matter are investigated experimentally. The diffusing fluid is a dye solution whose Schmidt number is about 3800, and five different jet Reynolds numbers, Re (≡U_0d/υ; U_0: mean velocity at the nozzle exit, d : diameter of the nozzle exit, υ : kinematic viscosity), are chosen, i.e., 6 600, 9 900, 13 300, 15 500 and 17 700. Simultaneous measurements of the axial and radial velocities and concentration have been made by a combined probe of X-type hotfilm and fiber-optic concentration sensor. It is found that the mass flux is not affected by the scale smaller than the scale of velocity fluctuation. The velocity-scalar cospectrum (or scalar flux spectrum) is also investigated. The axial velocity-concentration cospectra on the jet centerline show the -7/3 scaling law. And their scaling range agrees with the overlap range of the inertial subrange and the convective subrange. On the other hand, at some distance from the jet centerline (at γ/b_u = 0.73 ; γ ; radial distance from the jet axis, bu : half-width of the radial profile of axial mean velocity), the radial velocity-concentration cospectra show about -2 scaling law, but the axial velocity-concentration cospectra still show the - 7/3 scaling law.
2007-03-25