Air-borne sound generated by sea waves.

This paper describes a semi-empiric model and measurements of air-borne sound generated by breaking sea waves. Measurements have been performed at the Baltic Sea. Shores with different slopes and sediment types have been investigated.

Towards minimal perturbations in transitional plane Couette flow.

For parallel shear flows, transition to turbulence occurs only for perturbations of sufficiently large amplitude. It is therefore relevant to study the shape, amplitude, and dynamics of the least energetic initial disturbances leading to transition. We suggest a numerical approach to find such minimal perturbations, applied here to the case of plane Couette flow.

Turbulent spot evolution in spatially invariant boundary layers.

A demanding task, for successful fluid dynamic design in many industrial applications, is being able to predict the transition to turbulence location in boundary layer flows. The focus of the present experimental study is on the late stage of transition scenarios where turbulent spots are borne. We report on a natural stabilizing mechanism on the growth rate of turbulent spots, which takes place in a specific bypass transition scenario, and show that there is a palpable history effect of the origin of the turbulent spot on the streamwise evolution.

Heavy ellipsoids in creeping shear flow: transitions of the particle rotation rate and orbit shape.

The motion of an inertial ellipsoid in a creeping linear shear flow of a Newtonian fluid is studied numerically. This constitutes a fundamental system that is used as a basis for simulations and analysis of flows with heavy nonspherical particles. The torque on the ellipsoid is given analytically by Jeffery [Proc.

Flow effects on the acoustic end correction of a sudden in-duct area expansion.

For scattering of plane waves at a sudden area expansion in a duct, the presence of flow may significantly alter the reactive properties. This paper studies the influence of a mean flow field and unstable separated flow on the reactive properties of the expansion, formulated as an end correction. Theoretical and experimental results show that the expansion end correction is significantly affected by the flow and hydrodynamic waves excited at the edge of the expansion.

Multicomponent and multiphase modeling and simulation of reactive wetting.

A multicomponent and multiphase model with fluid motion is developed. The model is used to study reactive wetting in the case where concentration change of the spreading liquid and the substrate occurs. With the introduction of a Gibbs energy functional, the governing equations are derived, consisting of convective concentration and phase-field equations which are coupled to the Navier-Stokes equations with surface tension forces.

Microdroplet deposition under a liquid medium.

An experimental and numerical study of the factors affecting the reproducibility of microdroplet depositions performed under a liquid medium is presented. In the deposition procedure, sample solution is dispensed from the end of a capillary by the aid of a pressure pulse onto a substrate with pillar-shaped sample anchors. The deposition was modeled using the convective Cahn-Hilliard equation coupled with the Navier-Stokes equations with added surface tension and gravity forces.