Aerodynamic optimisation for a 62-pallet delivery vehicle

Assignment Brief

Handbook 4. 1CWK50 The Brief

The Brief

You are working as the Technical Engineering Advisor for a large DIY store. The payload of the vehicle is required to take 62 pallets of mixed palletised goods for delivery in the UK only. Goods are stored in central England at Coventry and the whole of UK is stocked from this hub. You are required to analyse the current vehicle specification to produce a vehicle body system that is aerodynamically optimised for both outward and the return journey. Use the provided CAD file and manufacturer`s specification to establish your baseline models and progress your simulations.

In your investigations, you should use the following assumptions:

1. No cross flow velocity component

2. Yaw angle is zero

3. Maximum legal speed 90kph

4. The simulation can be assumed to be steady-state i.e. no acceleration

5. Standard temperature and pressure conditions are considered for ambient atmosphere

6. The fluid is dry air zero moisture Note: If you make any other assumptions in your calculations please ensure you state these at the start of each calculation

Determine: Establish appropriate fluid domain and flow parameters and consider one or more of the following aspects:

1. The front and rear shape of the vehicle

2. The prime driver compartment and its interaction with the vehicle load

3. Any other aero aid devices that can be fitted that do not affect the legal compliance or load carrying capabilities of the combination

4. Any other modification that could be made to the outfit Values for the lift and drag should be calculated using different Reynolds numbers and appropriate analysis.

Evaluate:

Your aim is to create an aerodynamically optimised body system for both outward and return journeys performance, thus: reducing fuel consumption minimising the vehicle`s environmental impact reducing the overall operating cost

Sample Answer

Aerodynamic optimisation for a 62-pallet delivery vehicle

Executive summary

This report analyses a standard UK articulated delivery vehicle operating from a Coventry hub with a required payload of 62 pallets. The aim is to propose a vehicle body system optimised aerodynamically for both outward (loaded) and return (unloaded or partially loaded) journeys, while preserving legal load capacity and roadworthiness.

A baseline aerodynamic analysis is established from standard box trailer geometry: frontal area 10.2–10.98 m² (width 2.55 m, height assumed 4.0 m), cruise speed 90 kph (25.0 m/s), standard sea level conditions. Using a representative baseline drag coefficient Cd ≈ 0.90 for a blunt box trailer, the steady drag force at 90 kph is calculated as 3,514 N. A package of practical, legally compliant aerodynamic measures (roof fairing and gap reducer, side skirts, full-length undertray and deployable boat tail) reduces Cd to approximately 0.62 in the loaded configuration, lowering drag to 2,421 N, a 31% reduction in aerodynamic drag force. At 120,000 km/year typical duty, this equates to roughly 9,110 litres of diesel saved per vehicle per year and about 24.4 tonnes CO2 saved annually. Estimated annual fuel cost saving (at £1.50/l) is approximately £13,665.

Full details, domain setup, Reynolds number estimates, lift estimates and recommended validation/testing methods follow.

Scope, baseline assumptions and physical data

Task summary

Produce an aerodynamically optimised vehicle body system for a UK delivery truck that:

• carries 62 pallets (loaded outbound),

• operates at legal maximum speed of 90 kph on trunk roads/motorways,

• is optimised for both outward and return journeys,

• respects legal and load-carrying constraints.

Baseline geometric and operating assumptions

These are the assumptions used throughout calculations and simulation setup. If you prefer different dimensions, replace them consistently.

• Vehicle type: Standard UK articulated tractor + box trailer (palletised load).

• Trailer external dimensions (typical): length L = 13.6 m, width W = 2.55 m, height H = 4.0 m. Frontal area A = W × H = 2.55 × 4.0 = 10.2 m². For conservative estimates a nominal A = 10.98 m² (2.55 × 4.3) can be adopted if roof-mounted items are present. I use A = 10.2 m² in primary calculations. State whichever you use on submission.

• Speed: V = 90 kph = 25.0 m/s (steady, no acceleration).

• Ambient: standard sea level STP, ρ = 1.225 kg/m³, dynamic viscosity μ = 1.81 × 10⁻⁵ Pa·s. Dry air.

• Yaw = 0°, no crosswind component. Steady-state flow.

• Characteristic lengths for Reynolds number: use L = 13.6 m (vehicle length), and representative cross-section chord lengths for local flow Lc = 2.55 m (width) and 4.0 m (height) for boundary layer/local Re checks.

• Baseline aerodynamic coefficients (typical industry values): box trailer Cd ≈ 0.85–1.00; take Cd_base = 0.90 as baseline. Baseline lift coefficient CL_base ≈ +0.05 (small nose lift tendency). These are representative; precise Cd/CL should be derived from CFD/wind-tunnel.

Additional assumptions (stated for transparency)

• Centre of gravity and ride height remain in legal range when loaded; small modifications do not change legal axle weights or payload volume.

• Proposed aero devices are externally mounted or integrated into bodywork and do not reduce internal usable pallet volume. Retractable or removable versions are proposed for items that could affect loading operations if required.

• Structural and regulatory checks (VCA, DVSA) for body modifications will be completed prior to implementation; this report focuses on aerodynamic and operational performance.

Continued...