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# Computational Fluid Dynamics – General Transport Equation

1 - Question

The general equation applicable to all the properties is called the general transport equation. What does this term ‘transport’ signify?

a) The equation is applicable to all properties

b) The equation can be transformed easily

c) The equation includes various transport processes

d) The equation is general

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Answer: cExplanation: The general transport equation involves all the transport processes which are responsible for the transfer of mass, energy or other properties.

2 - Question

What are the terms included in the transport equation?

a) Rate of change term, advective term, convective term, source term

b) Advective term, diffusive term, convective term, source term

c) Rate of change term, diffusive term, convective term, advective term

d) Rate of change term, diffusive term, convective term, source term

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Answer: dExplanation: Transport equation involves four terms which are rate of change, diffusion, convection and source of properties.

3 - Question

What does the term ∂(ρΦ)∂t mean?

a) Rate of change

b) Convection

c) Diffusion

d) Source term

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Answer: aExplanation: This term represents the rate of change of fluid property inside the model of flow. It does not involve any kind of flow of the property.

4 - Question

Which of these terms represent the flow of fluid into and out of the observation model?

a) ∂(ρΦ)∂t

b) div(ρΦu⃗ )

c) div(ΓgradΦ)

d) ΓgradΦ

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Answer: bExplanation: div(ρΦu⃗ ) is the convective term of the transport equation. Convection is the flow of fluid into and out of the model of observation.

5 - Question

Which term represents the diffusion of the property Φ?

a) div(Φ)

b) div(ΓgradΦ)

c) curl(Φ)

d) curl(ΓgradΦ)

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Answer: bExplanation: div(ΓgradΦ) represents diffusion. Diffusion is the movement of fluid from a high concentration to low concentration within the system.

6 - Question

What does this symbol Γ in the term div(ΓgradΦ) of the general transport equation mean?

a) Diffusion flux

b) Convection coefficient

c) Diffusion coefficient

d) Rate of diffusion

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Answer: cExplanation: Γ represents the diffusion coefficient. The diffusion coefficient is defined by Fick’s law of diffusion.

7 - Question

In terms of heat transfer, what does div(ΓgradΦ) mean?

a) Heat radiation

b) Heat convection

c) Thermal flow

d) Heat conduction

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Answer: dExplanation: Diffusive heat transfer is called heat conduction. This refers to the process of heat transfer without any movement of the particles.

8 - Question

When the general transport equation is written in the energy equation form, what does Γ become?

a) k

b) μ

c) σ

d) κ

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Answer: aExplanation: k represents thermal conductivity. As diffusion in heat transfer is heat conduction, diffusion coefficient becomes, thermal conductivity.

9 - Question

Which of these statements hold true?

a) Diffusive flux is always positive

b) Diffusive flux is positive in the direction of the positive gradient of fluid property

c) Diffusive flux is positive in the direction of the negative gradient of fluid property

d) Diffusive flux is always negative

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Answer: cExplanation: Diffusive flux is positive in the direction of the negative gradient of fluid property. Example, heat is conducted in the direction of decreasing temperature.

10 - Question

To get the mass conservation equation from the general transport equation given below, Φ=?

∂(ρΦ)∂t+div(ρΦu⃗ )=div(ΓgradΦ)+SΦ

a) Mass of the fluid

b) 1

c) 0

d) Density of the fluid

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Answer: bExplanation: The mass conservation equation is obtained by replacing Φ with 1. As density is already present in the equation, 1 is enough to get mass conservation out of it.

11 - Question

The surface integral can be used to represent ____ and ____ terms of the transport equation.

a) Rate of change and diffusion

b) Rate of change and convection

c) Source and diffusion

d) Convection and diffusion

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Answer: dExplanation: Convection and diffusion terms are based on a transfer through the boundaries. The boundaries of a volume are its surfaces which makes surface integrals ideal for convection and diffusion.