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CAPE5320M Multiscale Modelling and Simulation
CFD Coursework, August 2025 Re-sit
Simulations of Turbulent Flow and Heat Transfer in an Axisymmetric Sudden
Expansion of a Circular Duct
Objective:
The objective of this coursework is to apply ANSYS FLUENT software to simulate: (i) turbulent flow
of water through an axisymmetric sudden expansion in a circular duct as illustrated in Figure 1,
and (ii) heat transfer in a confined water jet flowing through the same system.
Water Flow @ 20
oC

Inlet average velocity, Vin = 0.5 m s
1
Figure 1. Flow through an axisymmetric sudden expansion of a circular duct
Coursework Problems:
Problem-1: Turbulent flow in an axisymmetric sudden expansion of a circular duct (Fig. 1)
(a) Base case simulation: Carry out grid independence tests, sensitivity of the prediction on the
near-wall grid distributions, inlet and wall boundary conditions using the first order upwind
discretisation scheme for the convection terms of the Reynolds-averaged Navier-Stokes
(RANS) equations and the standard k- model for turbulence.
The selected final grid and boundary conditions must be used to solve problems (b)-(d).
(b) Effect of convective discretisation scheme: Investigate the effect of the second order
upwind discretisation scheme on the predicted flow characteristics using the k- turbulence
model. Compare the results with those obtained using the first order upwind scheme in the
base case simulation (problem-1(a)).
(c) Effect of turbulence modelling: Investigate the effect of the following turbulence models on
the predicted flow characteristics using the second order upwind scheme:
(i) Shear stress transport (SST) model,
(ii) Reynolds-Stress model (RSM).
Compare the results with those obtained for problem-1(b) using the k- model.
School of Chemical and Process Engineering
Vin
2.0 m
1.0m
4.0 m
D1= 0.1 m D2 = 3D1
(d) Effect of inlet water velocity: Investigate the effect of the inlet water velocity (i.e., Re) on the
flow pattern for Vin in the range 0.3 to 0.6 m s
1 using the best discretisation scheme and
turbulence model based on the simulation cases (b) and (c).
Problem-2: Heat transfer in a confined water jet
Investigate the turbulent flow and heat transfer phenomena in a water jet issuing into an
axisymmetric sudden expansion geometry, as shown in Figure 1. The inlet velocity and
temperature of the water jet are given in Figure 1. The duct wall temperature is 80
oC. Use the best
convective discretisation scheme, the turbulence model, grid and boundary conditions found in
problem-1.
Assessment of Coursework:
The coursework is worth 40% and will be assessed based on a report including CFD simulation
results and analysis of problems #1 & 2. In the generation and presentation of results, attention
should be directed to the following issues:
1. Computational strategy to obtain reliable solutions (i.e., grid optimisation, grid independency,
convergence level, overall mass/energy balances, boundary conditions, etc.).
2. Effective presentation of results (i.e., drawing attention to important features of the flow,
using appropriate types of graph, etc.).
3. Validation of CFD results against theory and experimental data reported in the literature.
Deadline for the submission of CFD coursework: 2pm on Monday 11th August 2025
Tariq Mahmud / 10-07-2025
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