MEC320 CFD MOCK exam

What is the physical meaning of the local derivative?

The time rate of change at a fixed point.

what mathematically describes a three-dimensional incompressible flow, steady state or transient.

What is the Stokes relationship

Relationship between viscous stresses, and velocity gradients.

What is the definition of 𝑢+?

The ratio of velocity parallel to the wall to the friction velocity

What is Reynolds stress

Stress due to velocity fluctuations

What do k and ε stand for

Turbulent kinetic energy and its dissipation rate per unit mass

Express the turbulence velocity scale in terms of k and ε

𝑘^1/2

Let Cμ be a dimensionless constant and ρ be the density of the flow. Express the dynamic eddy viscosity in terms of turbulence kinetic energy (k) and a turbulence time scale (𝜏)

𝜌𝐶𝜇𝑘𝜏

Select the incorrect statement.

a) The low-Reynolds number model requires no wall function.

b) The low-Reynolds number model is for low-Reynold number flow only.

c) The low-Reynolds number model requires 𝑦+ < 1.

d) The low-Reynolds number model considers viscous effect near the wall.

(B)

The Reynolds stress turbulence model is particularly useful if the flow is

Dominated by swirl

Which of these is an advantage of the Finite Difference Method over the Finite Volume Method?

a) Conservativeness

b) Higher-order

c) Stability

d) Complex problems

(B)

C

The numerical convection schemes are often upwind biased for ———-

Better stability

The number of discretized equations is equal to the number of ———-

Discretized internal cells

The CFL (Courant–Friedrichs–Lewy number) number should normally be kept

<1 C=U·Δt/Δh

U = flow velocity or wave speed

Δt = time step size

Δh = spatial grid size (cell size)

The SIMPLE algorithm is a ———

Predictor-corrector method

CFD packages solve the algebraic equations of flow using ____________ method.

Iterative

The aim of the mesh independence study is to understand the —-

Effect of mesh resolution

A solution is ideally converged if _________

the residuals fall below some pre-set criterion