This set of Computational Fluid Dynamics Multiple Choice Questions & Answers (MCQs) focuses on “Discretization Aspects – Transportiveness”.
1. Transportiveness has an influence on _________
a) the discretization scheme
b) the solution method for an algebraic system of equations
c) the mathematical model
d) the iterative scheme
View Answer
Explanation: Transportiveness is borne by the discretization scheme. An appropriate method of discretization should be chosen based on the transportiveness of the system.
2. Which of these is related to the transportiveness?
a) Courant number
b) Reynolds number
c) Nusselt number
d) Peclet number
View Answer
Explanation: Peclet number defines the transportiveness of a fluid flow property. The Peclet number has a direct impact on the isolines of a flow property around a specific node.
3. Peclet number is a ratio of _________ strength to the _________ strength.
a) Diffusive, convective
b) Convective, diffusive
c) Radiative, diffusive
d) Diffusive, radiative
View Answer
Explanation: Peclet number defines how much convection flux dominates the diffusion flux of fluid flow. It will decide if the transport of flow property is because of convection or diffusion.
\(Peclet\, number=\frac{Convective\, strength}{Diffusive\, strength}\).
4. When the Peclet number is zero, the isolines are ___________
a) hyperbolic
b) elliptic
c) circular
d) parabolic
View Answer
Explanation: When the Peclet number is zero, the isolines of flow property are circular with the current node at its centre. Here, diffusive strength dominates.
5. When the Peclet number is large, the isolines are ___________
a) hyperbolic
b) circular
c) elliptic
d) parabolic
View Answer
Explanation: When the Peclet number is large, convection dominates the flow of a property. Here, the isolines will be elliptic with the current node at its focus.
6. When the Peclet number is zero, the value of flow property at the current node is influenced by ___________
a) the upstream node more
b) both the upstream and downstream nodes equally
c) the downstream node more
d) neither the upstream nor the downstream nodes
View Answer
Explanation: When the Peclet number (convection) is zero, flow direction does not affect the value of flow property. Both the upstream and the downstream nodes have equal influence on the value at the current node.
7. When the Peclet number is large, the value of flow property at the current node influences ___________
a) the upstream node more
b) both the upstream and downstream nodes equally
c) neither the upstream nor the downstream nodes
d) the downstream node more
View Answer
Explanation: The impact of flow property is affected by the flow direction when the Peclet number is large. The current node is affected by the upstream node and it affects the downstream node.
8. When transportiveness is not accounted in the discretization scheme, the solution becomes ___________
a) unstable
b) non-converging
c) inaccurate
d) non-conservative
View Answer
Explanation: Transportiveness must be taken care of while choosing the discretization scheme. If not, solutions will have unphysical oscillations and become unstable.
9. Why are isolines circular when the Peclet number is zero?
a) Fluid is flowing and diffusion spreads equally
b) Fluid is stagnant and diffusion spreads equally
c) Fluid is stagnant and diffusion spreads directionally
d) Fluid is flowing and diffusion spreads directionally
View Answer
Explanation: When the Peclet number is zero, the problem is dominated by diffusion. This means that the fluid is stagnant. Diffusion allows the flow of property to spread in the domain equally in all the directions.
10. Which of these schemes will suit a flow with a low Peclet number?
a) Iterative schemes
b) Backward differencing scheme
c) Central differencing scheme
d) Forward differencing scheme
View Answer
Explanation: When the Peclet number is low, the central differencing scheme can be used. This is because, in this case, the flow variable is affected by both of the neighbouring nodes equally.
Sanfoundry Global Education & Learning Series – Computational Fluid Dynamics.
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