Abstract
A radially symmetric slow flow system in a long cylinder with moderate wall leakage is considered, with physical parameters taken from the renal proximal tubule. Dimensional analysis yields a simplified system which, under certain assumptions, is well-posed, and possesses a unique solution if a solution exists. A lumped parameter analysis generates a one-dimensional model identical to a typical one-dimensional model in a special case. The one- and two-dimensional models agree well in the situations examined. When the wall fluxes are of a certain class, the concentration to which the solution tends as the fluid proceeds down the tubule can be computed algebraically.
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Abbreviations
- a, b:
-
terms in example inequalities
- A, B, C, D:
-
real-valued functions of a scalar variable on [0, 1]
- c:
-
concentration
- c0,c1,c2 :
-
constants
- C0,C1, C2 :
-
constants
- D:
-
diffusion coefficient
- d1, d2 :
-
scalar domains
- f(r):
-
factor of nondimensional concentration
- F:
-
flux
- g(y):
-
factor of nondimensional concentration
- G:
-
gas constant
- h(r):
-
function arising from a solution of the PDM
- I:
-
interval of integration
- Js :
-
solute flux averaged over axial variable
- K:
-
constant
- kj :
-
constant associated with wall solute pump: j=1, constant pump; j=2, pump ∝ concentration
- L:
-
length of PT
- Lp :
-
hydraulic conductivity of wall of PT
- M:
-
volume flow into PT from glomeralus
- p:
-
pressure
- P:
-
permeability of PT to solute
- Q:
-
flow resistance
- r:
-
radial variable
- R:
-
radius of PT
- Re:
-
Reynolds number
- S:
-
nondimensional constant
- Sc:
-
Schmidt number
- u:
-
axial velocity averaged over radial variable
- v:
-
velocity
- x:
-
limit of integration
- y:
-
axial variable
- Y:
-
number in the interval [0, 1]
- z:
-
dummy variable
- α:
-
constant
- γ:
-
dimensionless concentration-1
- δ:
-
ratio of tubule radius to length
- Δ:
-
difference between value inside and outside PT at wall
- ɛ:
-
small positive parameter
- μ:
-
viscosity
- ϱ:
-
density
- φ:
-
decimal percentage of fluid leaving the PT through the walls
- σ:
-
reflection coefficient
- ω:
-
dummy variable
- f:
-
fixed value
- i:
-
value at glomerular end of PT
- 0:
-
value at distal end of PT
- r:
-
radial
- s:
-
solute; serosa
- v:
-
volume
- y:
-
axial
- ∞:
-
limiting value
- -:
-
log mean
- ~:
-
used to distinguish between the function ci(r) and the constant ci
- boldface:
-
dimensional
- normal typeface:
-
dimensionless
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Morrish, K. Performance of one- and two-dimensional models for a slow flow system in a long, permeable tubule. J. Math. Biol. 24, 237–258 (1986). https://doi.org/10.1007/BF00275636
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DOI: https://doi.org/10.1007/BF00275636