Chinese Journal of Computational Physics ›› 2021, Vol. 38 ›› Issue (5): 521-533.DOI: 10.19596/j.cnki.1001-246x.8347

Special Issue: 多孔介质毛细动力学研究

• Special Topics on Capillary Dynamics in Porous Media • Previous Articles     Next Articles

Tolman Length-based Modified Lucas-Washburn Capillary-driven Model and Numerical Simulation

Junjie WANG1(), Jisheng KOU1, Jianchao CAI2, Yixin PAN1, Zhen ZHONG1,*()   

  1. 1. School of Civil Engineering, Shaoxing University, Shaoxing, Zhejiang 312002, China
    2. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
  • Received:2021-02-28 Online:2021-09-25 Published:2022-03-24
  • Contact: Zhen ZHONG

Abstract:

The classical Lucas-Washburn (L-W) capillary-driven model calculates capillary pressure using the Young-Laplace equation, which leads to a deviation from the real values for a pipe with small diameter. In this work we use Tolman length to improve the Young-Laplace equation, and propose an improved L-W model. Moreover, circular pipes with rough and variable sections are considered rather than the circular pipe with a constant diameter. Relation between time and wetting fluid injection length in the circular pipe with variable sections is established. The mathematical model is described as a second-order nonlinear ordinary differential equation, which cannot be solved analytically, and thus an efficient numerical method is developed. A concrete pipe with variable cross-section is selected, and the relation between water length and time is calulated with numerical simulation. Numerical results are analyzed, and the effectiveness of Tolman length is verified. It shows that the local shrinkage of circular pipe changes the states of water motion significantly, and there are three kinds of movement modes. The local expansion of circular pipe changes slowly the state of seepage and water absorption, and only one single movement mode takes place.

Key words: capillarity, Lucas-Washburn equation, nonlinear differential equation, Tolman length, numerical simulation

CLC Number: