Free Surface Flow in a Microfluidic Corner and in an Unconfined Aquifer with Accretion

The Signorini and Saint-Venant Analytical Techniques Revisited

A. R. Kacimov, D. V. Maklakov, I. R. Kayumov, A. Al-Futaisi

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Steady, laminar, fully developed flows of a Newtonian fluid driven by a constant pressure gradient in (1) a curvilinear constant cross section triangle bounded by two straight no-slip segments and a circular meniscus and (2) a wedge bounded by two rays and an adjacent film bulging near the corner are studied analytically by the theory of holomorphic functions and numerically by finite elements. The analytical solution of the first problem is obtained by reducing the Poisson equation for the longitudinal flow velocity to the Laplace equation, conformal mapping of the corresponding transformed physical domain onto an auxiliary half-plane and solving there the Signorini mixed boundary value problem (BVP). The numerical solution is obtained by meshing the circular sector and solving a system of linear equations ensuing from the Poisson equation. Comparisons are made with known solutions for flows in a rectangular conduit, circular annulus and Philip’s circular duct with a no-shear sector. Problem (2) is treated by the Saint-Venant semi-inverse method: the free surface (quasi-meniscus) is reconstructed by a one-parametric family, which specifies a holomorphic function of the first derivative of the physical coordinate with respect to an auxiliary variable. The latter maps the flow domain onto a quarter of a unit disc where a mixed BVP for a characteristic function is solved by the Zhukovsky–Chaplygin method. Velocity distributions in a cross section perpendicular to the flow direction are obtained. It is shown that the change of the type of the boundary condition from no slip to perfect slip (along the meniscus) causes a dramatic increase of the total flow rate (conductance). For example, the classical Saint-Venant formulae for a sector, with all three boundaries being no-slip segments, predict up to four times smaller rate as compared to a free surface meniscus. Mathematically equivalent problems of unconfined flows in aquifers recharged by a constant-intensity infiltration are also addressed.

Original languageEnglish
Pages (from-to)115-142
Number of pages28
JournalTransport in Porous Media
Volume116
Issue number1
DOIs
Publication statusPublished - Jan 1 2017

Fingerprint

Aquifers
Microfluidics
Poisson equation
Boundary value problems
Conformal mapping
Laplace equation
Velocity distribution
Linear equations
Pressure gradient
Infiltration
Flow velocity
Ducts
Flow rate
Boundary conditions
Derivatives
Fluids

Keywords

  • Meniscus
  • Poisson equation
  • Signorini formula
  • Viscous film
  • Zhukovsky–Chaplygin method
  • Zunker’s pendular water slug

ASJC Scopus subject areas

  • Catalysis
  • Chemical Engineering(all)

Cite this

Free Surface Flow in a Microfluidic Corner and in an Unconfined Aquifer with Accretion : The Signorini and Saint-Venant Analytical Techniques Revisited. / Kacimov, A. R.; Maklakov, D. V.; Kayumov, I. R.; Al-Futaisi, A.

In: Transport in Porous Media, Vol. 116, No. 1, 01.01.2017, p. 115-142.

Research output: Contribution to journalArticle

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