Behavior of Motile Sperm in Taylor-Couette Flow: Effect of Shear Stress on the Behavior of Motile Sperm

Infertility is often cited as one of the causes of a declining birthrate, which has become a serious social problem in recent years. Processes by which motile sperm can be safely and easily sorted are therefore important for infertility treatment. Therefore, as a new sorting method, microfluidic sperm sorter using the microfluidic system has been developed. To improve more separation efficiency of this device, it is necessary to know the behaviors of motile sperm in the microchannel where the sperm undergo shear flow. The previous study implied the necessity of the modeling of motile sperm in the shear flow. In the present study, therefore, we experimentally investigated the behavior of the motile sperm in the Taylor-Couette flow using PTV (Particle Tracking Velocimetry) method. The experimental results showed that the ascent of the shear stress led to the increase in the sperm velocity, and the direction of the sperm velocity was opposite to that of the flow.

Experimental Study of the Viscous Pump with a Helical Channel Rotor:Torsion Effect of the Channel

The viscous pump,which has a rotor with a helical square channel,is studied experimentally.The non-dimen-sional channel curvature is taken to be about 0.1.Three types of torsion of the channel are made to investigate the torsion effect on the flow characteristics.We measure the flux through the channel at a constant rotor speed by changing the pressures at the entrance and exit of the pump.We also observe the secondary flow at a cross-section of the channel.Some of the results obtained are shown as follows:The friction factor along the channel to get the same flux is large for large channel torsion at a constant rotation,and becomes small when the favorable rotation of the rotor to the flow is applied.As for the secondary flow in a cross-section,there appear several types of vortex.When there is no rotation,the secondary flow is almost a symmetric two-vortex type for small flux as is the ordinary Dean vortex,but it changes to a four-vortex type when the flux is large.The secondary flow becomes asymmetric as the rotation is applied.We have unsteady flow patterns at large flux and rotation.

Experimental Study of the Flow in Helical Circular Pipes:Torsion Effect on the Flow Velocity and Turbulence

现在的纸的一个目的是试验性地在螺旋状的圆形的管子中在流动上澄清扭转效果。我们使六成为了有不同程度和大约 0.1 的普通非维的弯曲 δ 的螺旋状的圆形的管子。被 β0=τ/(2 δ) 定义的扭转参数 β0, 有非维的扭转 τ 的 1/2 ，被拿是 0.02， 0.45， 0.69， 1.01， 1.38 和 1.89 盖住从对很大的沥青小。速度分布和流动的骚乱从 200 ～ 20000 在雷纳兹数字的范围用一张 X 类型热电线的风速表被测量。获得的结果如下被总结：在管子的生气的节的吝啬的第二等的流动模式从没有扭转(toroidal 管子) ，在之一以后在一根弄弯的管子中被看见到一种单个旋涡类型的一种平常的成双旋涡的类型变化成双旋涡当 β0 增加，逐渐地消失。单个旋涡的循环方向与管子的扭转的方向一样。轴流的吝啬的速度分发类似于在小 β0, 的 toroidal 管子的，但是当 β0 在一根笔直地圆形的管子中增加，并且到达类似于那的形状，改变它的形状什么时候 β0= 1.89。这也被发现批评雷纳兹数字，流动在显示出边缘的行为到骚乱，为小 β0, 作为 β0 增加减少然后在拿在 β0≈ 的最小以后增加1.4 作为 β0 增加。试验性地获得的批评雷纳兹数字的最小在 β0≈ 是大约 4001.4。