COMPLETE ITN - ETN NETWORK

1. Numerical analysis by using Lagrangian Turbulence spectral solvers of the transport of energy, water vapour and droplets across the interface warm cloud/clear air in a stably and non-stably stratified environment.
2. Lagrangian analysis of small inertial water droplets in suspension (1 -100 micron) across turbulent-non turbulent cloud interfaces and inside warm clouds.
3. Inclusion of effects associated to buoyancy and condensation/evaporation.

Analysis of data produced by innovative expendable bio-compatible radio-probes released and floating in warm clouds. Comparison of field data with numerical simulations.

1. Study of particles (aerosols/droplets) in interfacial dynamics either in shear-free mixing layers where the interface is between two different turbulent intensity fields or in cases where the interface will be between a turbulent and a non-turbulent field.
2. Study of interfaces as they appear in wakes and jets to simulate in the laboratory and the computer the kind of turbulent/non-turbulent interfacial physics which may be found in clouds under certain conditions.

1. Numerical study (Direct Numerical Simulation) of the interaction between the flow interface and an approximately collocated buoyancy interface
2. Influence of the nonlinear dependence of buoyancy on mixing fraction in clouds, and how these enhance/reduce turbulent exchange
3. Dynamics of buoyant inertial particles
    

• Experimental measurement of the acceleration and relative velocity of micrometric droplets in warm clouds in situ at the research station Schneefernerhaus.
• Numerical scheme capable of reproducing the experimental results.

• To develop a drop generator capable of rapid creation of liquid droplets of sizes 5-50 µm, similar to those typically found in warm clouds.
• To control also the initial velocity of the created drops, both in magnitude and direction.
• Experimental measurement of the coalescence rate of droplets generated with the device.

Experimental and numerical based estimates of "apparent diffusivity" of particles and fluid parcels crossing the turbulent/non-turbulent interfaces with density jumps.

- To develop and improve an ultrafast temperature, velocity and humidity probe following the design of the NSTAP (nanoscale thermal anemometry probe) family patented by Hultmark et al. in 2014 and outlined in e.g. "Nanoscale sensing devices for turbulence measurements" by Fan et al., Exp Fluids (2015). The innovative design of the NSTAP probes makes them prime candidates for the development of ultrafast probes of within multiphase flows such as clouds, due to their already superior robustness to cloud-particle impacts.

The project is aimed at joint investigation of droplet spatial distribution and small-scale turbulence in clouds. We plan to measure positions and velocities of cloud droplets in a two-dimensional plane enlightened by a laser sheet technique. We will build a device allowing for uniform illumination of cloud volume of the area ~50x50 cm2 and of variable thickness (~1mm to ~2cm).

The project is aimed at numerical modelling of transport and interactions of Stokes particles, such as cloud droplets and other aerosols (WP 3, 4). In high Reynolds number flows, say in a cumulus cloud, there is a gap of 2-4 decades between the Kolmogorov scale and the size of transported droplets. Therefore, even Direct Numerical Simulations of the flow require sub-grid scale (SGS) modelling to account for droplet transport and interactions within one grid cell.

• Computing balloon Lagrangian trajectories from LES outputs in shallow cumulus and stratocumulus conditions.  
• Comparison with data from mini radioprobes from WP2.
• Specific adjustement to Lagrangian trajectories will have to be implemented to take into account balloon dynamics.
• Rates of mixing will be estimated at the interfaces of cloudy and clear air.

1. Testing on the field of the sensing probes.
2. Pre-processing of data acquired by the ground station.

The aim is to propose numerical new procedures to implement droplet nucleation models inside codes where the cloud interface is studied by coupling the Eulerian description of the turbulent velocity and water vapour fields with a Lagrangian ensemble of cloud water droplets that can undergo stochastic nucleation, as well as growth and shrinking by condensation and evaporation, respectively.

Design and Development of microelectronic systems for innovative sensors control: feasibility studies, the size estimation, power and package definition, application circuit study, breadboard implementation, electrical specifications definition, testing-oriented design definition, optimization of system dimensions and weight, identification of materials with low environmental impact.

Tracking small-scale Lagrangian fluctuations inside warm clouds using innovative low-power/low-cost sensors. Development of the trajectory tracking algorithm for the radiosonde by using INS (Inertial Navigation System) and GNSS (Global Navigation Satellite System) sensors. Design and develop a data acquisition system for managing Lagrangian dataset.

Development of mini green radio-probes. Analysis of data produced by innovative expendable bio-compatible radio-probes released and floating in warm clouds. Comparison of field data with numerical simulations.

Passive scalars (temperature and/or supersaturation) and a Lagrangian subroutine (to compute particle displacement and supersaturation) will be installed to ICL’s in-house Navier-Stokes solver “Incompact3d” code so that the detailed dynamics of the turbulent/non-turbulent interface can be investigated. The project will also aim at the application of this approach to a broader range of turbulent flows.