本文以流場可視化法及PIV量測法研究靜止外罩內同步旋轉雙圓盤間流場之動力特性。流場可視化法利用雷射光頁照射懸浮質點以顯現量測平面上之流動結構。雙圓盤間之流體會因圓盤與轉軸幾何變化關係及不同轉速而形成具規則外型之多邊形流動結構。多邊形流動結構之外型轉換受到雷諾數與轉軸幾何之影響：轉軸外徑較大時，造成流動結構外型轉換之雷諾數較小。多邊形流動結構與圓盤並不同步轉動，其轉動頻率相對於圓盤頻率之比值為—五邊形：0.8；四邊形：0.75；三角形：0.69；橢圓形：0.6。PIV量測獲得速度時序資料，以時間平均及相位解析法進行分析，得到速度場及紊流特性。速度時序資料以頻譜分析獲得定量化之流場特徵頻率，該特徵頻率與流場可視化所認知之現象一致。時間平均速度分佈之斜率隨徑向位置改變，自轉軸至外罩間可分為四個特徵區域：似固體轉動區(solid-body-rotation-like region)、過渡區(buffer region)、渦旋結構區(vortex region)及外罩影響區(shroud-influenced region)。相位解析法所獲得之相對速度向量及流線圖均顯示在多邊形流動結構與外罩間存在渦旋結構，且該渦旋結構之數量與多邊形流動結構之邊數相同。紊流分析將瞬時速度分解成時間平均項、週期性波動項及紊流擾動項，據以研究各擾動項對於流場中紊流特性之影響。分析結果顯示，整體擾動強度分佈區域內之極大及極小值位置與週期性波動強度一致。雷諾應力分析結果，流場中周向及徑向雷諾正向應力高於雷諾剪應力。而雷諾剪應力分佈極大值出現在過渡區與渦旋結構區之間，顯示該位置具有明顯紊流動量交換現象。Lagrangian時間與尺寸之積分尺度分佈與多邊形流動結構及流場特徵區域有明顯關係。

Flow characteristics in the interdisk midplane between two shrouded co-rotating disks were experimentally studied. A laser-assisted particle-laden flow-visualization method was used to identify the qualitative flow behaviors. Particle image velocimetry was employed to measure the instantaneous flow velocities. The flow visualization revealed rotating polygonal flow structures (hexagon, pentagon, quadrangle, triangle, and oval) existing in the core region of the interdisk spacing. There existed a difference between the rotating frequencies of the polygon and the disks. The rotating frequency ratio between the polygonal flow structure and the disks depended on the mode shapes of the polygonal flow structures—0.8 for pentagon, 0.75 for quadrangle, 0.69 for triangle, and 0.6 for oval. The radial distributions of the time-averaged and phase-resolved ensemble-averaged circumferential and radial velocities were presented. Five characteristic regions (solid-body-rotation-like region, buffer region, vortex region, and shroud-influenced region) were identified according to the prominent physical features of the flow velocity distributions. The phase-resolved, ensemble-averaged relative radial velocity profiles in the interdisk midplane at various phase angles exhibited grouping behaviors in three ranges of polygon phase angles (θ = 0 and α/2, 0 < θ < α/2, and α/2 < θ < α). Circumferential and radial turbulence intensities, Reynolds stresses, turbulence kinetic energy, correlation coefficients, as well as the Lagrangian integral time and length scales of turbulent fluctuations were analyzed and presented. Features of the turbulence properties were found to be closely related to the rotation motion of the inner and outer characteristic flow structures. The circumferential components of the turbulence properties exhibited local minima in the buffer region and maxima in the solid-body rotation and vortex regions, while the radial components of the turbulence intensity, turbulent normal stress, and Lagrangian integral turbulence time scale exhibited maximum values in the buffer region and relatively low values in the regions near the hub and the shroud.

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