论文标题
渠道流中湍流的发作，尺度不变的粗糙度
Onset of turbulence in channel flows with scale-invariant roughness
论文作者
论文摘要
使用Navier的3D直接数值模拟 - Stokes方程，我们研究了壁粗糙度对通道流中湍流发作的影响。发现摩擦因子对雷诺数的依赖性$ \ mathrm {re} $，遵循了概括的Forchheimer定律，该法在层层和惯性渐近线之间进行了插值。这两个渐近线之间的过渡发生在第一个关键的$ \ mathrm {re} $，$ \ mathrm {re} _ {\ mathrm {c}} $，这在非试图取决于粗糙度的glimate。我们通过查看速度波动对不同的粗糙度振幅的依赖性来确定从亚临界到超临界发作的过渡。我们发现，第二个关键$ \ mathrm {re} $的幅度与$ \ mathrm {re} _ {\ mathrm {c}} $相当，这意味着当$ \ mathrm {re} $和粗糙度宽容时，过渡流是开放流中不可或缺的一部分。
Using 3D direct numerical simulations of the Navier--Stokes equations, we study the effect of wall roughness on the onset of turbulence in channel flow. The dependence of the friction factor on the Reynolds number, $\mathrm{Re}$, is found to follow a generalized Forchheimer law, which interpolates between the laminar and inertial asymptotes. The transition between these two asymptotes occurs at a first critical $\mathrm{Re}$, $\mathrm{Re}_{\mathrm{c}}$, that depends nontrivially on the roughness amplitude. We identify the transition from subcritical to supercritical onset by looking at the dependence of the velocity fluctuations on Re for different roughness amplitudes. We find that this second critical $\mathrm{Re}$ is comparable in magnitude to $\mathrm{Re}_{\mathrm{c}}$, implying that transitional flow is an integral part of flow in open fractures when $\mathrm{Re}$ and the roughness amplitude are sufficiently high.
