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Abstract

サリバン渦は発達した竜巻の2セル構造に類似した特徴をもつ,ナヴィエ-ストークス方程式の厳密解である.本研究ではサリバン渦の線形安定性を調べた.サリバン渦の対称軸方向(鉛直方向)に一様性をもつ水平二次元擾乱を仮定した場合と,三次元擾乱の場合の両方で線形安定性解析を行い,どちらの場合でも方位角方向波数が小さい擾乱が発達しうることを示した.三次元擾乱を考えた場合,サリバン渦の水平流のシアと鉛直流のシアのどちらの効果が大きいかによって,発達モードの構造が変化する.サリバン渦の鉛直方向の広がりを無限遠方まで考えた場合,鉛直流のシアの効果が大きくなり,線形安定性解析では任意の渦レイノルズ数において不安定となる.ただし,渦レイノルズ数が10^4オーダーの場合には,水平流のシアの効果によって,鉛直方向の広い範囲において,水平二次元的擾乱の発達が卓越しうる.Sullivan vortex is an exact solution of the Navier-Stokes equations and it has a two-cell vortex structure similar to mature tornadoes. In this study, we investigate linear stability of Sullivan vortex to either horizontal two-dimensional disturbances, which is vertically (in the direction of the axis of symmetry of Sullivan vortex) uniform, or three-dimensional disturbances. In both cases, Sullivan vortex is found to be unstable to disturbances of low azimuthal wavenumbers. For three-dimensional disturbances, the structures of growing modes change depending on whether the horizontal shear flow or the vertical shear flow has more significant effect. In the context of linear stability analysis, Sullivan vortex is unstable for any vortex Reynolds number because of strong effect of vertical shear flow if we consider that Sullivan vortex extends infinitely in the vertical direction. If vortex Reynolds number is the order of 10^4, however, horizontal two-dimensional disturbances can grow within a wide range in the vertical direction.

Journal

  • ながれ : 日本流体力学会誌 = Nagare : journal of Japan Society of Fluid Mechanics

    ながれ : 日本流体力学会誌 = Nagare : journal of Japan Society of Fluid Mechanics 33(1), 47-60, 2014-02

    日本流体力学会

Codes

  • NII Article ID (NAID)
    110009809567
  • NII NACSIS-CAT ID (NCID)
    AN00175191
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    0286-3154
  • NDL Article ID
    025380137
  • NDL Call No.
    Z14-911
  • Data Source
    NDL  NII-ELS 
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