Resistance of velocity slip flow in pipe/channel with a sudden contraction

Sun, Qiangqiang; Choi, Kwing So; Zhao, Yong; Mao, Xuerui

Abstract

© 2020 Author(s). A novel approach based on the local entropy generation rate, also known as the second law analysis (SLA), is proposed to compute and visualize the flow resistance in mass transfer through a pipe/channel with a sudden contraction component (SCC) at low Reynolds number (Re) featuring velocity slip. The linear Navier velocity slip boundary condition is implemented using the explicit scheme. At small Reynolds number, i.e., Re ≤ 10.0, the flow resistance coefficient of the SCC, KSCC, is found to be a function of the dimensionless velocity slip length Lslip∗ and Re-1, and gradually increase to a constant value at contraction ratio Rarea ≥ 8, reaching a formula KSCC=(0.4454Lslip∗ 3-1.894Lslip∗ 2+2.917Lslip*+8.909)/Re. Over this range of Re, the equivalent length of the flow resistance is almost independent of Re, while out of this range, the equivalent length increases monotonically with Re. Moreover, the dimensionless drag force work around the SCC is negative and reaches a minimum at a critical Lslip*. The SLA reveals that the regions affected by the SCC mainly concentrate around the end section of the upstream pipe/channel rather than the initial partition of the downstream section reported in large Re turbulent flow, and this non-dimensional affected upstream length increases with Lslip*. The fluid physics are further examined using SLA to evaluate the energy loss over the entire domain, decomposed as the viscous dissipation inside the domain and the drag work on the wall boundary.

Citation

Sun, Q., Choi, K. S., Zhao, Y., & Mao, X. (2020). Resistance of velocity slip flow in pipe/channel with a sudden contraction. Physics of Fluids, 32(6), Article 063602. https://doi.org/10.1063/5.0009415

• Journal Article Type: Article
• Acceptance Date: Jun 2, 2020
• Online Publication Date: Jun 18, 2020
• Publication Date: Jun 1, 2020
• Deposit Date: Jun 2, 2020
• Publicly Available Date: Jun 2, 2020
• Journal: Physics of Fluids
• Print ISSN: 1070-6631
• Electronic ISSN: 1089-7666
• Publisher: American Institute of Physics
• Peer Reviewed: Peer Reviewed
• Volume: 32
• Issue: 6
• Article Number: 063602
• DOI: https://doi.org/10.1063/5.0009415
• Keywords: Condensed Matter Physics
• Public URL: https://nottingham-repository.worktribe.com/output/4564231
• Publisher URL: https://aip.scitation.org/journal/phf
• Additional Information: Received: 2020-04-01; Accepted: 2020-06-02; Published: 2020-06-18