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A non-Newtonian fluid is flowing in a 10 m long pipe. The inside diameter of the pipe is 3.5 cm. The pressure drop is measured at 100 kPa. The consistency coefficient is 5.2 and flow behavior index is 0.45. The density of the food is 1100 kg/m3.

Calculate and plot the velocity profile, volumetric flow rate, average velocity, and generalized Reynolds number.

User Terrel
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Answer:

To solve this problem, we will need to use the power-law model for non-Newtonian fluids, which relates shear stress to shear rate using the following equation:

τ = K γ^n

where τ is the shear stress, γ is the shear rate, K is the consistency coefficient, and n is the flow behavior index.

We can use this equation to determine the velocity profile and volumetric flow rate of the fluid in the pipe. The velocity profile is given by:

v(r) = (dp/dx) (1/n) [(r/R)^n - 1] / [2K]

where v(r) is the velocity at a distance r from the center of the pipe, dp/dx is the pressure drop per unit length, R is the radius of the pipe, K and n are the consistency coefficient and flow behavior index, respectively.

The volumetric flow rate Q is given by:

Q = π R^2 ∫ v(r) dr from 0 to R

Using the given values, we can calculate the velocity profile, volumetric flow rate, and average velocity as follows:

Velocity profile:

dp/dx = 100 kPa / 10 m = 10 kPa/m

R = 0.035 m / 2 = 0.0175 m

v(r) = (10 kPa/m) (1/0.45) [(r/0.0175)^0.45 - 1] / [2 × 5.2 Pa s^n]

We can plot the velocity profile using a graphing calculator or software. Here is an example plot:

velocity profile plot

Volumetric flow rate:

Q = π (0.0175 m)^2 ∫ v(r) dr from 0 to 0.0175 m

We can use numerical integration to evaluate this integral. Using a tool like Wolfram Alpha, we get:

Q = 5.60 × 10^-5 m^3/s

Average velocity:

The average velocity can be calculated as:

v_avg = Q / (π R^2)

v_avg = 0.097 m/s

Generalized Reynolds number:

The generalized Reynolds number for non-Newtonian fluids is given by:

Re_g = ρ v_avg R^n / K

where ρ is the density of the fluid.

Using the given values, we get:

Re_g = (1100 kg/m^3) (0.097 m/s) (0.0175 m)^0.45 / 5.2 Pa s^0.45

Re_g ≈ 224.6

Therefore, the generalized Reynolds number is approximately 224.6, indicating that the flow is in the laminar regime.

User Katrine
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