ダクト内バックステップ流れの熱伝達に関する数値解析（流体粒子軌踖のパターンにつぃて）

摘要

本研究で注目するバックステップ流れは，はく離と再rn付着を伴う流れ系の中で最も基礎的であり，主として乱rn流の数値解析モデルの検証を目的として，多くの実験rn的・数値解析的研究が行われてきた流れ系である（1）~(6)．rnこれまでの研究では，ステップ流路のスパン方向幅を十rn分大きくとり，流れが二次元であるとみなせるような場rnに関心が集まっていた．しかし，ステップ背後に生成さrnれる循環流域において，実際の多くの機器に存在する側rn壁の影響が少なからずあることのが指摘され，最近ではrn側壁の影響を考慮に入れた流れの三次元性に関する研究rnが進められてぃる．%Three-dimensional flow and thermal fields have been solved numerically for the stepped duct laminar flow for different inlet flow conditions, uniform flow and fully developed flow. Attention has been paid to the particle trajectories over the step and their relation to the spatial distributions of the heat transfer coefficient on the bottom wall behind the step. Fluid particles entering the flow re-circulation behind the step was found to be started from the small limited area in the vicinity of the side wall for both inlet flow conditions. Such particles, in the uniform flow case, move toward the center of the duct forming spiral motions and they flow downstream one by one before they reach to the center of the duct. However, in developed inlet flow case, such particles proceed together until they reach the center of the duct showing large unique spiral motion and then they flow downstream from the center of the duct. Owing to this, low heat transfer coefficient is obtained at the center of the duct and low heat transfer area becomes larger compared to that in the uniform inlet flow case.