JOB DESCRIPTION

Stratified flows, where fluid density and viscosity vary strongly, are common in both natural and industrial systems—ranging from ocean currents to advanced heat exchangers. However, conventional models like the Boussinesq approximation fail to capture the complex physics in such flows when strong stratification or non-ideal fluids are involved.
This PhD project aims to advance our understanding of turbulence in stratified shear flows by studying a supercritical CO2 flow, differentially heated in a channel, using high-resolution optical experiments. You will design and conduct measurements with advanced techniques such as particle image velocimetry (PIV) and background-oriented Schlieren (BOS) to capture flow behavior in regimes that were previously inaccessible.

Key tasks include:

• Implementing and validating optical measurement techniques (PIV and BOS) in a high-pressure, optically accessible flow loop.
• Performing precise flow measurements under varying temperature and pressure conditions to generate strong stratification.
• Investigating the transition from laminar to turbulent flow, including the identification of flow structures such as turbulent spots and instability waves.
• Developing correction strategies for refractive index effects and tracer particle behavior due to strong density gradients.
• Collaborating with a numerical PhD researcher to compare experimental results with linear stability theory and direct numerical simulations.

The work is embedded in a broader project combining theory, simulations, and experiments. While the experimental setup uses supercritical CO2 to access extreme stratification, the insights gained will have broad implications for the understanding and control of stratified shear flows in various engineering and environmental applications.

JOB REQUIREMENTS

We are looking for a motivated and curious candidate with:

• A Master’s degree (or equivalent) in mechanical engineering, applied physics, aerospace engineering, or a related field.
• A strong background in fluid mechanics and experimental methods.
• Hands-on experience with optical diagnostics such as particle image velocimetry (PIV), Schlieren techniques, or similar laser-based measurement methods is a strong plus.
• Affinity for working with complex lab setups, instrumentation, and high-pressure systems.
• The ability to work independently as well as collaboratively in a multidisciplinary team.
• Good command of English, both written and spoken.

• Implementing and validating optical measurement techniques (PIV and BOS) in a high-pressure, optically accessible flow loop.
• Performing precise flow measurements under varying temperature and pressure conditions to generate strong stratification.
• Investigating the transition from laminar to turbulent flow, including the identification of flow structures such as turbulent spots and instability waves.
• Developing correction strategies for refractive index effects and tracer particle behavior due to strong density gradients.
• Collaborating with a numerical PhD researcher to compare experimental results with linear stability theory and direct numerical simulations