The classical transition from laminar to turbulent flow is affected if solid particles are added. The transition behavior is a function of particle size $d$ and solid volume fraction $\varphi$ and the flow undergoes a smooth transition, as opposed to intermittent, if $\varphi$ exceeds a certain threshold. In this work we show that, for particle-laden pipe flows with large particle-to-pipe diameter ratios $d/D$, the $\varphi$ threshold for altering the transition is much lower than previously reported for smaller particles. Magnetic resonance velocimetry reveals that particles introduce turbulent-like fluid velocity fluctuations in laminar flow. Factors that might control the limits between “classical” and “smooth” transition in the state space spanned by $d/D$ and $\varphi$ are discussed based on scaling analyses.

中文翻译：

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大颗粒的管道流动及其对湍流过渡的影响

如果添加固体颗粒，则会影响从层流到湍流的经典过渡。过渡行为是粒径的函数$d$ 和固体体积分数 $\varphi$ 且与间歇性相反，流动经历了平稳过渡 $\varphi$超过某个阈值。在这项工作中，我们表明，对于颗粒直径较大的管道​​，颗粒与管道的直径比大$d/d$， $\varphi$改变过渡的阈值比以前报道的较小颗粒低得多。磁共振测速表明，颗粒在层流中引入了湍流状的流体速度波动。可能控制状态空间中“经典”和“平滑”过渡之间的限制的因素$d/d$ 和 $\varphi$ 基于定标分析讨论。