Air quality has become a major concern for public health as it causes respiratory and cardiovascular diseases, cancer, diabetes, and premature deaths. Air pollutants can be gaseous or solid particles (also referred as particulate matter). The impact of pollutants not only depend on the emitted quantity but also on other factors such as the proximity to sources and the dispersion conditions. The automotive sector makes a significant contribution to local air pollution and exposes the population to dangerous levels of pollutants. To reduce pollutant emissions, the automotive sector focused on reducing fuel consumption by decreasing the vehicle drag. This approach reduced pollutant emissions generated by road vehicles. However, the levels of pollutant emissions need to be further reduced.

To properly understand the transport and dispersion mechanisms, a good knowledge of the flow region where the pollutants are emitted is needed, which happens to be the wake flow behind a vehicle. Recent studies have revealed a strong relationship between the flow structures and the pollutant concentrations in the wake of simplified vehicle models. Different wake flow features (such as vortices, shear layers, and the recirculation region) play a major role in the mixing and dispersion of particulate and gaseous pollutants. These studies were conducted in wind tunnels under ideal conditions (low inflow turbulence intensity, laminar boundary layer, stationary ground). On one hand, highly controlled test conditions are required to enhance the basic understanding of the wake flow phenomena. On the other hand, ideal test conditions are often unrealistic. Solutions have been developed to introduce realistic road conditions in wind tunnel testing such as the introduction of a rolling road to reproduce ground effects (roughness), yaw angle variations to consider realistic crosswind configuration, and inflow turbulence conditions. The aim of this PhD study is to further understand the governing aerodynamic processes in the wake flow of realistic car shapes and their implications on pollutant dispersion under actual road conditions.

 

Overview

The PhD student will test these two hypotheses:

  • There is a strong effect of the vehicle shape on the wake flow and aerodynamic drag,
  • There is a direct link between the topology of wake flow and the dispersion of pollutants.

To test these two hypotheses, the PhD student will:

  • Investigate the effects of different parameters on the wake flow such as yaw angle, vehicle shape (realistic shapes), inflow turbulence, and ground roughness,
  • Compare results of Ahmed bodies (simplified) and DrivAer models (realistic),
  • Correlate experiments and simulations to come up with the best methodology.

The bi-stability wake flow phenomena of DrivAer models are yet to be fully understood in the context of pollutant dispersion. Prior studies focused more on drag reduction rather than pollutant dispersion. This PhD study aims to fill this gap by addressing public health and environmental issues.

 

What will you Learn

The main objectives of this project are:

  • Characterisation of the flow developing in the wake of an Ahmed body (reference case). Both steady and unsteady studies will be conducted for different experimental conditions (yaw angles of the model), natures of the incident flow turbulence, and roughness of the ground). The results can be compared to available data in the literature (especially in the framework of the collaboration with Concordia University),
  • Characterisation of the flow developing in the wake of a DrivAer model. Both steady and unsteady studies will be conducted for experimental conditions with different yaw angles, natures of the incident flow, and roughness of the ground. The results will be compared with those available in the literature,
  • Â鶹´«Ã½AV of the effect of a rolling road (relative movement of the ground) on the wake. To achieve this goal, measurements will be carried out at Cranfield using experimental conditions studied with a fixed floor at ESTACA. The influence of the car model, ground roughness, incident turbulence and yaw angle will be discussed,
  • Characterisation of steady and unsteady flows (determination of the characteristic time and length scales of the flow). For this, we will rely on preliminary results obtained by Edwin Duran-Garcia which will be extended to the proposed PhD project. Additional developments may be made depending on the progress of the work,
  • Numerical simulations will be carried out at Cranfield in the continuity of what is done by considering the new experimental developments. For these CFD studies, numerical tools and super computers at Cranfield and Loughborough will be available,
  • On-road experimental data will be provided by industry (Emissions Analytics), which will enable us to bridge the gap between wind tunnel and actual road conditions.

 As it is a double-PhD study, the student will spend the first 18 months at Cranfield (Shrivenham campus) in the UK and the last 18 months at ESTACA (Bordeaux campus) in France. As part of this double-PhD study, we collaborate with industry (Emissions Analytics) and academia (Loughborough University).

 

Expected Impact

The PhD research findings will enable us to make recommendations to improve air quality in passenger car cabins (for commuters) and for cyclists and pedestrians (huge costs in terms of public health). These findings are expected to have academic (writing scientific publications), economic (developing passenger cars), and societal (mitigating public health issues) impact.

 

Unique Selling Points

The student will attend mandatory courses (how to publish?; ethics in research integrity; open access). The student will participate in 3-minute PhD presentations and poster competitions. The student will present research findings at international conferences to disseminate novel findings to the international scientific community. The student will attend training on scientific writing as the research findings will be published in high-impact journals. The student will attend relevant workshops to develop both technical and transferrable skills.

The student will have training for laser Doppler anemometry (LDA) and computational fluid dynamics (CFD). The student will have placements at industry (Emissions Analytics) and academia (Loughborough). As it is a double-PhD study, the student will get familiar with both British and French academic systems. The student will attend relevant courses (introduction to Python; statistical analysis) to further develop academic knowledge and technical skillset. The student will receive hands on experience on experimental and computational techniques through advanced training from senior colleagues. The student will attend relevant personal development courses. The student will be part of the doctoral community and present the research findings at its annual conference.

 

Location of Â鶹´«Ã½AV

Based at the UK Defence Academy at Shrivenham in Oxfordshire, CDS is the academic provider to the UK Ministry of Defence for postgraduate education at the Defence Academy, training in engineering, science, acquisition, management and leadership.

At a glance

  • Application deadline03 Sep 2025
  • Award type(s)PhD
  • Start date06 Oct 2025
  • Duration of award3 years
  • EligibilityUK, EU
  • Reference numberCDS087

Entry requirements

Applicants should have a UK first or second class honours degree in automobile engineering or mechanical engineering or aerospace engineering with a focus on thermofluids / aerodynamics.

To be eligible for this fully-funded PhD studentship, applicants must be a UK national or an EU national who qualifies for home fee status in the UK.


Funding

This is a fully-funded, 3-year, full-time PhD studentship, which covers all fees at a UK level, tax-free stipend (£19,000 per year for 3 years), and running costs (£10,000 over a period of 3 years), which include travel and subsistence, conference / training fees, laboratory consumables.

How to apply

For information about applications please contact: CDSAdmissionsoffice@cranfield.ac.uk 

A CV and short cover letter justifying your case to secure the opportunity is required.

If you are eligible to apply for this PhD, please complete