The image above represents diffusivity constant.

To compute for the diffusivity constant, four essential parameters are needed and these parameters are **pemerability (k), porosity (φ), viscosity (μ) and total compressibility (C _{T}).**

The formula for calculating diffusivity constant:

η = ^{0.000263k} / _{φμC}_{T}

Where;

η = Diffusivity Constant

k = Permeability

φ = Porosity

μ = Viscosity

C_{T} = Total Compressibility

Let’s solve an example;

Find the diffusivity constant where the permeability is 12, porosity is 9, viscosity is 7 and total compressibility is 11.

This implies that;

k = Permeability = 12

φ = Porosity = 9

μ = Viscosity = 7

C_{T} = Total Compressibility = 11

η = ^{0.000263k} / _{ φμC}_{T}

η = ^{0.000263 x 12} / _{9 x 7 x 11}

η = ^{0.003156} / _{693}

η = 0.000004554112554112554

Therefore, the **diffusivity constant **is **0.000004554112554112554**.

**Calculating the Permeability when the Diffusivity Constant, Porosity, Viscosity and Total Compressibility is Given.**

k = ^{n x φμCT} / _{0.000263}

Where;

k = Permeability

η = Diffusivity Constant

φ = Porosity

μ = Viscosity

C_{T} = Total Compressibility

Let’s solve an example;

Find the permeability where the diffusivity constant is 24, porosity is 10, viscosity is 5 and total compressibility is 13.

This implies that;

η = Diffusivity Constant = 24

φ = Porosity = 10

μ = Viscosity = 5

C_{T} = Total Compressibility = 13

k = ^{n x φμCT} / _{0.000263}

k = ^{24 x 10 x 5 x 13} / _{0.000263}

k = ^{15600} / _{0.000263}

k = 59315589.3536

Therefore, the **permeability** is **59315589.3536**.

**Calculating the Porosity when the Diffusivity Constant, Permeability, Viscosity and Total Compressibility is Given.**

φ = ^{0.000263k} / _{nμC}_{T}

Where;

φ = Porosity

k = Permeability

η = Diffusivity Constant

μ = Viscosity

C_{T} = Total Compressibility

Let’s solve an example;

Find the porosity where the diffusivity constant is 28, permeability is 8, viscosity is 12 and total compressibility is 18.

This implies that;

k = Permeability = 8

η = Diffusivity Constant = 28

μ = Viscosity = 12

C_{T} = Total Compressibility = 18

φ = ^{0.000263k} / _{nμC}_{T}

φ = ^{0.000263 x 8} / _{28 x 12 x 18}

φ = ^{0.002104} / _{6048}

φ = 3.478e-7

Therefore, the **porosity **is **3.47e-7.**

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