The averaged flows excited by oscillations of fluid in an axisymmetric channel, which transverse section periodically changes with longitudinal coordinate, are experimentally studied. Oscillations are caused by harmonious change of a volume of the fluid, which is pumped over via the channel. Researches are executed within the broad range of dimensionless frequency which characterizes the ratio of the cross size of the channel to the thickness of Stokes boundary layers. It is shown that oscillations of fluid excite an averaged flows in the form of a system of toroidal vortex structures in each segment of the channel. The intensity of averaged flows increases with the increase in amplitude and frequency of fluid oscillation and is defined by the pulsational Reynolds number and the dimensionless frequency in the channel of the set geometry. It is shown that in the limit of low dimensionless frequencies, when viscous forces define the oscillating component of flow in the whole channel, the primary vortices occupy all the volume of the channel. The cross size of the primary vortices decreases with the increase in dimensionless frequency, and at high frequencies the vortexes are localized in viscous boundary layer near the side border in a narrow part of the channel. At the same time, the secondary vortices having opposite turning are formed outside the primary boundary layer vortexes in the bulk of the channel. The transformation of the structure of averaged flows and their intensity versus the dimensionless frequency are studied.

中文翻译：

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可变截面的轴对称通道中的流体稳态流动与无量纲频率的关系

实验研究了轴对称通道中流体振荡激发的平均流量，该流量的横截面随纵向坐标周期性变化。振荡是由通过通道泵送的流体体积的和谐变化引起的。在无因次频率的广泛范围内进行研究，该频率表征了通道的交叉尺寸与斯托克斯边界层厚度的比值。结果表明，流体的振荡以通道每个段中环形涡旋结构系统的形式激发平均流量。平均流量的强度随着流体振荡的幅度和频率的增加而增加，并且由脉动雷诺数和设定几何形状的通道中的无量纲频率来定义。结果表明，在低无量纲频率的极限中，当粘性力定义了整个通道中流动的振荡分量时，初级涡旋占据了通道的所有体积。初级涡流的交叉尺寸随无量纲频率的增加而减小，并且在高频时，涡流位于通道狭窄部分侧边界附近的粘性边界层中。同时，在通道的主体中的主要边界层涡旋的外侧形成了具有相反转向的次要涡旋。研究了平均流量的结构转换及其强度与无量纲频率的关系。主旋涡占据了通道的所有体积。初级涡流的交叉尺寸随无量纲频率的增加而减小，并且在高频时，涡流位于通道狭窄部分侧边界附近的粘性边界层中。同时，在通道的主体中的主要边界层涡旋的外侧形成了具有相反转向的次要涡旋。研究了平均流量的结构转换及其强度与无量纲频率的关系。主旋涡占据了通道的所有体积。初级涡流的交叉尺寸随无量纲频率的增加而减小，并且在高频时，涡流位于通道狭窄部分侧边界附近的粘性边界层中。同时，在通道的主体中的主要边界层涡旋的外侧形成了具有相反转向的次要涡旋。研究了平均流量的结构转换及其强度与无量纲频率的关系。在通道的主体中的主要边界层涡旋的外部形成具有相反转向的次要涡旋。研究了平均流量的结构转换及其强度与无量纲频率的关系。在通道的主体中的主要边界层涡旋的外部形成具有相反转向的次要涡旋。研究了平均流量的结构转换及其强度与无量纲频率的关系。