Computational Fluid Dynamics Practice Test 5

1. When compared to the algorithm to calculate the gradient of a structured grid, the algorithm for unstructured grids ___________

is more accurate

need more computational cost

need less computational cost

is less accurate

2. Expand the term \(\rho_{i,j}^{t+\Delta t}\) for the MacCormack’s technique.
Note:
t →Current time-step
av → Average time-step between t and t+Δ t.

\(\rho_{i,j}^{av}+(\frac{\partial\rho}{\partial t})_{i,j}^t \Delta t\)

\(\rho_{i,j}^t+(\frac{\partial\rho}{\partial t})_{i,j}^t \Delta t\)

\(\rho_{i,j}^{av}+(\frac{\partial\rho}{\partial t})_{i,j}^{av} \Delta t\)

\(\rho_{i,j}^t+(\frac{\partial\rho}{\partial t})_{i,j}^{av}\Delta t\)

3. How are the faces of a 3-D element divided to find the area?

Quadrilaterals

Rectangles

Squares

Triangles

4. What is the order of accuracy for the method of numerical approximation represented by this diagram?

Fourth-order

First-order

Third-order

Second-order

5. The direction of the normal to a face in an unstructured mesh depends upon __________

Global indices

Direction of flow

Local indices

Direction of increasing indices

6. Which value is predicted in the predictor step of the MacCormack’s technique?

Variable at the upcoming time-step

Variable at the average time-step

Time derivative of the variable at the average time-step

Time derivative of the variable at the upcoming time-step

7. What is the order of accuracy of the midpoint rule approximation?

Fourth-order

First-order

Third-order

Second-order

8. Consider a 3-D problem. Non-overlapping elements can be created by joining __________

cell-centroids and face-centroids

face-centroids and edge-centroids

cell-centroids, face-centroids and edge-centroids

cell-centroids and edge -centroids

9. To find the volume and centroid of a polyhedral, it is divided into ____________

Pyramids

Polygons

Hexahedrons

Quadrilaterals

10. The cost of computation for Fourier coefficients can be reduced by ___________

FFT

IFT

IDFT

DFT