Determining the viscosity of ionic solution

[sharmilan]

Dear Phreeqc experts,

for my moisture transport model, I need to update the viscosity of the ionic solution in every timestep. is there any method or keyword that has been adapted in the PHREEQC code for determining the viscosity of ionic solution? 

Thank you
sharmilan.

[dlparkhurst]

There are Basic functions VISCOS and VISCOS_0, however, they both return the viscosity of pure water under the conditions of the calculation. The functions do not account for the effect of solutes.

[sharmilan]

Thank you for reply

is a function of VISCOS calculating only the effect of temperature on viscosity of pure water or includes any other condition?

Thank you
sharmilan.

[dlparkhurst]

Viscos_0 only takes into account the temperature effect on the viscosity of pure water.

Viscos is set equal to Viscos_0 for all of the databases of PHREEQC.

Tony Appelo has written the capability for PHREEQC to read viscosity parameters for the Jones-Dole and Falkenhagen-Dole equations in SOLUTION_SPECIES with an undocumented option for a species -viscosity. 10 viscosity parameters are required for each species. I don't think Tony was satisfied with the results, so the parameters have never been assembled. The following is a comment related to the viscosity calculation in the method transport.cpp:viscosity. I am not familiar with the calculation, so this is all I know.

   /* (modified) Jones-Dole eqn for viscosity:
   viscos / viscos_0 =
   1 + A * eq_tot^0.5 +
   f_an * (Sum(B_i * m_i) +
   Sum(D_i * m_i * ((1 + f_I) * mu_x^d3_i + (m_i * f_z)^d3_i) / (2 + f_I)))
   A calculated from Falkenhagen-Dole
   B_i = b0 + b1*exp(b2 * tc), b0..2 in Jones_Dole[0..2], read in SOLUTION_SPECIES
   D_i = d1 * exp(d2 * tc), d1, 2 in Jones_Dole[3, 4]
   d3_i in Jones_Dole[5]
   Jones_Dole[6] contains the anion factor, 1 for Cl-, variable for other anions
   f_z = (z * z + |z|) / 2, the contribution of the ion to mu_x, if z = 0: f_z = mu_x / m_i
   f_I = variable, depends on d3_i > 1, or d3_i < 1.
   tc is limited to 200 C.


   A from Falkenhagen-Dole for a salt:
   A = 4.3787e-14 * TK**1.5 / (eps_r**0.5)* (z1 + z2)**-0.5 / (D1 * D2) * psi
   psi = (D1*z2 + D2*z1)/4 - z1*z2 * (D1-D2)**2 / ((D1*z1 + D2*z2)**0.5 + ((D1 + D2) * (z1 + z2))**0.5)**2
   D1, z1 for the cation, D2, |z2| for the anion of the salt.
   We use the harmonic mean of the Dw's, and the arithmetic mean of the z's,
   both weighted by the equivalent concentration. */