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New Approach on the General Shape Equation of Axisymmetric Vesicles
The general Helfrich shape equation determined by minimizing the curvature
free energy describes the equilibrium shapes of the axisymmetric lipid bilayer
vesicles in different conditions. It is a non-linear differential equation with
variable coefficients. In this letter, by analyzing the unique property of the
solution, we change this shape equation into a system of the two differential
equations. One of them is a linear differential equation. This equation system
contains all of the known rigorous solutions of the general shape equation. And
the more general constraint conditions are found for the solution of the
general shape equation.Comment: 8 pages, LaTex, submit to Mod. Phys. Lett.
Forchheimer flow to a well-considering time-dependent critical radius
Previous studies on the non-Darcian flow into a pumping well assumed that
critical radius (RCD) was a constant or infinity, where RCD
represents the location of the interface between the non-Darcian flow region
and Darcian flow region. In this study, a two-region model considering
time-dependent RCD was established, where the non-Darcian flow was
described by the Forchheimer equation. A new iteration method was proposed
to estimate RCD based on the finite-difference method. The results
showed that RCD increased with time until reaching the quasi steady-state flow, and the asymptotic value of RCD only depended on the
critical specific discharge beyond which flow became non-Darcian. A larger
inertial force would reduce the change rate of RCD with time, and
resulted in a smaller RCD at a specific time during the transient flow.
The difference between the new solution and previous solutions were obvious
in the early pumping stage. The new solution agreed very well with the
solution of the previous two-region model with a constant RCD under
quasi steady flow. It agreed with the solution of the fully Darcian flow
model in the Darcian flow region
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