On the Effect of Stably Stratified Layer to the Development of Free Convection

稳定层结层对自由对流发展的影响

• 批准号: 16540402
• 负责人: KARASUDANI Takashi
• 金额: $ 1.28万
• 依托单位: KYUSHU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2004
• 资助国家: 日本
• 起止时间: 2004 至 2005
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16540402/
• 关键词: stably stratified; mixed layer; inversion layer; air-sea exchange; stripe structures; turbulent transport; buoyancy driven turbulence; free convection; 対流; 混合層; 乱流; 交換過程; 熱輸送; 筋状構造; 大気-海洋境界面

Turbulence structure and transport process beneath the gas-liquid interface is important in air-sea interaction and in many industrial operations. As, in stably stratified circumstances (with inversion layer), turbulence parallel to vertical direction is suppressed, turbulence structure is expected to be affected greatly. To clarify the effect, we experimentally and numerically studied the development and statistical properties of a free convective layer under a water surface. Velocity and temperature fluctuations were simultaneously measured by a laser-Doppler velocimeter and a fine thermocouple. Variances and correlations for the fluctuations were normalized by the kinematic heat flux and the thickness of the convective layer, and vertical profiles of those quantities were obtained.Their profiles were compared with those for neutral circumstances (without inversion layer). The variance of the horizontal velocity decrease more slowly near the inversion layer, compared to neutral circumstances. The value of the correlation between temperature and vertical velocity became positive near the inversion layer, whereas the value was always non-positive in neutral circumstances.The situation was numerically simulated by DNS method. The calculated profiles of the variances were consistent with the experimental ones. By the simulation with various boundary conditions at the surface, it was found that stripe structure, which appeared in near the surface, was supposed to be generated by shear stress at the surface. There was no significant difference for the variances by the difference of the boundary conditions.

气液界面下的湍流结构和输运过程在海气相互作用和许多工业操作中都是非常重要的。由于在稳定层结(有逆温层)的情况下，平行于垂直方向的湍流被抑制，预计湍流结构将受到较大影响。为了阐明这种影响，我们用实验和数值方法研究了水面下自由对流层的发展和统计特性。用激光多普勒测速仪和精密热电偶同时测量了速度和温度的波动。用运动热通量和对流层厚度对波动的方差和相关性进行了归一化，得到了这些量的垂直廓线，并将它们的廓线与中性情况下(没有逆温层)的廓线进行了比较。与中性情况相比，逆温层附近的水平速度方差减小较慢。在逆温层附近，温度与垂直速度的相关值趋于正值，而在中性条件下，温度与垂直速度的相关值始终为非正值，并用数值模拟方法进行了数值模拟。方差的计算值与实验值吻合较好。通过对表面不同边界条件的模拟，发现在近表面出现的条状结构可能是由表面的剪应力产生的。边界条件的不同对方差的影响不显著。

项目成果

対流境界層の直接数値シミュレーション-水槽実験との比較-

对流边界层直接数值模拟-与水箱实验的比较-

• 发表时间: 2005
• 期刊: 第19回数値流体力学シンポジウム
• 作者: K.Tanaka;M.Ikeda;S.Setou;Y.Wakata;K.Iga;K.Iga;和方吉信;田中潔;伊賀啓太;水野宏樹;Y.Wakata;T.Karasudani;城野 良一
• 通讯作者: 城野 良一

対流混合層の発達について

对流混合层的发展

• 发表时间: 2005
• 期刊: 日本機会学会流体工学部門講演会講演概要集
• 作者: K.Tanaka;M.Ikeda;S.Setou;Y.Wakata;K.Iga;K.Iga;和方吉信;田中潔;伊賀啓太;水野宏樹;Y.Wakata;T.Karasudani;城野 良一;城野 良一
• 通讯作者: 城野 良一

Evolution and Structure of the Free Convective Layer Developing under a Water Surface

水面下发展的自由对流层的演化和结构

• 发表时间: 2006
• 期刊: JSME International Journal, Environmental Flows
• 作者: K.Tanaka;M.Ikeda;S.Setou;Y.Wakata;K.Iga;K.Iga;和方吉信;田中潔;伊賀啓太;水野宏樹;Y.Wakata;T.Karasudani
• 通讯作者: T.Karasudani