A Reynolds equation governing the steady flow of a fluid through a curvilinear, narrow tube, with its derivation from Navier–Stokes equations through asymptotic methods is presented. The channel considered may have a rather large curvature and torsion. Approximations of the velocity and the pressure of the fluid inside the channel are constructed by artificially imposing appropriate boundary conditions at the inlet and the outlet. A justification for the approximations is provided along with a comparison with a simpler case.

中文翻译：

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流经弯管的稳定流的修正雷诺方程

提出了控制流体通过弯曲的窄管的稳定流动的雷诺方程，并通过渐近方法从Navier–Stokes方程推导了该方程。所考虑的通道可能具有相当大的曲率和扭曲。通过在入口和出口处人为地施加适当的边界条件，可以构造通道内部流体的速度和压力的近似值。提供了近似的理由以及与较简单情况的比较。