A generic approach to parameterize the turbulent energy of single-epoch atmospheric delays from InSAR time-series

The observed phase in time series of interferometric synthetic aperture radar (InSAR) products is a superposition of various components. Differential topography, line-of-sight displacements, and differential atmospheric delays are the main contributions and need to be disentangled to derive accurate digital elevation model (DEM), deformation,...

Towards predicting cavitation noise using scale-resolving simulations: The importance of inflow turbulence

There is increasing attention for the effects of anthropogenic underwater radiated noise (URN) on marine fauna. This is expected to lead to regulations with respect to the maximum permitted sound emissions of ships. It is known that cavitating tip vortices, generated by ship propellers, are some of the key contributors to URN. Consequently,...

Observed scales of short-lived nocturnal turbulent structures

Nocturnal weather can have significant impact on society. Dangerous conditions can occur after clear sky nights with weak winds. The lack of turbulent mixing during these nights can cause the near-surface temperature to rapidly decrease. A single short-lived turbulent event can renew turbulent mixing and hamper/stop the formation of fog or...

Numerical Methods for the Optimization of Nonlinear Residual-Based Sungrid-Scale Models Using the Variational Germano Identity

The Variational Germano Identity [1, 2] is used to optimize the coefficients of residual-based subgrid-scale models that arise from the application of a Variational Multiscale Method [3, 4]. It is demonstrated that numerical iterative methods can be used to solve the Germano relations to obtain values for the parameters of subgrid-scale models...

Long-term unsteadiness and large-scale structures in Rayleigh-Bénard convection with and without electromagnetic forcing

This dissertation focuses on turbulent thermal convection, which occurs in a wide range of (geo)physical situations, like in the atmosphere, the oceans, the interior of stars or planets, and engineering applications, like metal casting or crystal growth processes. In this work, a special type of thermal convection, Rayleigh-Bénard convection, is...

On the scaling and unsteadiness of shock induced separation

Shock wave boundary layer interactions (SWBLI) are a common phenomenon in transonic and supersonic flows. The presence of shock waves, induced by specific geometrical configurations, causes a rapid increase of the pressure, which can lead to flow separation. Examples of such interactions are found in amongst others rocket engine nozzles and on...

On the required Reynolds-number dependence of variational multi-scale Smagorinsky models

A theoretical analysis is presented on the dependence of the standard and variational multi-scale Smagorinsky models on the proximity of the LES filter width Delta to the integral length scale of turbulence L on the one hand, and to the Kolmogorov scale eta on the other hand. Moreover modifications of the models are formulated, which respond...

Scales and structures in bubbly flows. Experimental analysis of the flow in bubble columns and in bubbling fluidized beds

In this project a detailed experimental analysis was performed of the dynamic flow field in bubbly flows, with the purpose of determining local hydrodynamics and scale effects. Measurements were done in gas-liquid systems (air-water bubble columns) and in gas-solid systems (air-sand bubbing fluidized beds) of different size. Amongst others with...

Development of a Two-Scale Turbulence Model and Its Applications

The use of second order closure turbulence model in predicting turbulent flows is known to be more successful than the classical mixing length model. However, it is found that if the turbulence constants are not altered or modified, the second order closure turbulence model is unable to predict satisfactorily f or some flows such as round jet...