当前位置: X-MOL 学术Flow Turbulence Combust. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Consistent Flow Structure Evolution in Accelerating Flow Through Hexagonal Sphere Pack
Flow, Turbulence and Combustion ( IF 2.0 ) Pub Date : 2020-06-09 , DOI: 10.1007/s10494-020-00168-4
Yoshiyuki Sakai , Michael Manhart

Direct numerical simulation based on incompressible Navier–Stokes equations with an immersed boundary method is used to simulate accelerating porous media flow through a bed of uniform spheres arranged in hexagonal close packing order. The transient flow is realised by driving initially resting fluid by a constant pressure gradient. A wide spectrum of Reynolds number based on the sphere diameter and volume-averaged velocity is considered, which ranges from creeping flow up to a Reynolds number of approximately 350, where turbulent flow structures are evident inside the pores. It is found that nonlinear dependence of the volume-averaged velocity with respect to the applied pressure gradient is the consequence of emergence of streamwise jets and the accompanying streamwise vortices, as previously observed for other sphere pack arrangements. Furthermore, two distinct flow modes are identified in the steady flow regime which satisfy full geometric symmetries. The flow then becomes unsteady around Reynolds number of 90 which coincides with a partial breaking of the symmetries, and pore-scale turbulence emerges once all the symmetries vanish when Reynolds number is larger than 200. For all the considered unsteady flow, independent of being turbulent or not, we observe a consistent sequence of flow structure evolution during the flow development with progressively broken symmetries albeit at widely varying instantaneous Reynolds numbers. Moreover, we show that the symmetry breaking takes place in larger pore spaces first, then propagate into smaller pores located in downstream.

中文翻译:

加速流过六边形球包的一致流结构演化

基于不可压缩 Navier-Stokes 方程和浸入边界法的直接数值模拟用于模拟加速多孔介质流过以六边形密堆积顺序排列的均匀球体床。瞬态流动是通过恒定压力梯度驱动最初静止的流体来实现的。考虑了基于球体直径和体积平均速度的广泛雷诺数,其范围从蠕动流到大约 350 的雷诺数,其中孔隙内的湍流结构很明显。发现体积平均速度相对于施加的压力梯度的非线性依赖性是流向射流和伴随的流向涡流出现的结果,如先前观察到的其他球包排列。此外,在满足完全几何对称性的稳定流动状态中识别出两种不同的流动模式。然后流动在雷诺数为 90 附近变得不稳定,这与对称性的部分破坏相吻合,当雷诺数大于 200 时,一旦所有对称性消失,就会出现孔隙尺度湍流。 对于所有考虑的不稳定流动,与湍流无关与否,我们观察到流动发展过程中流动结构演变的一致序列,对称性逐渐破坏,尽管瞬时雷诺数变化很大。此外,我们表明对称性破坏首先发生在较大的孔隙空间中,然后传播到位于下游的较小孔隙中。然后流动在雷诺数为 90 附近变得不稳定,这与对称性的部分破坏相吻合,当雷诺数大于 200 时,一旦所有对称性消失,就会出现孔隙尺度湍流。 对于所有考虑的不稳定流动,与湍流无关与否,我们观察到流动发展过程中流动结构演变的一致序列,对称性逐渐破坏,尽管瞬时雷诺数变化很大。此外,我们表明对称性破坏首先发生在较大的孔隙空间中,然后传播到位于下游的较小孔隙中。然后流动在雷诺数为 90 附近变得不稳定,这与对称性的部分破坏相吻合,当雷诺数大于 200 时,一旦所有对称性消失,就会出现孔隙尺度湍流。 对于所有考虑的不稳定流动,与湍流无关与否,我们观察到流动发展过程中流动结构演变的一致序列,对称性逐渐破坏,尽管瞬时雷诺数变化很大。此外,我们表明对称性破坏首先发生在较大的孔隙空间中,然后传播到位于下游的较小孔隙中。对于所有考虑的非定常流动,无论是否湍流,我们观察到流动发展过程中流动结构演变的一致序列,对称性逐渐破坏,尽管瞬时雷诺数变化很大。此外,我们表明对称性破坏首先发生在较大的孔隙空间中,然后传播到位于下游的较小孔隙中。对于所有考虑的非定常流动,无论是否湍流,我们观察到流动发展过程中流动结构演变的一致序列,对称性逐渐破坏,尽管瞬时雷诺数变化很大。此外,我们表明对称性破坏首先发生在较大的孔隙空间中,然后传播到位于下游的较小孔隙中。
更新日期:2020-06-09
down
wechat
bug