Experimental investigation of influence of an air cavity on a turbulent boundary layer using PIV

The turbulent boundary layer development under the influence of an air cavity is studied experimentally using planar PIV, with the aim of gaining insight and building upon the flow physics typically encountered in the application of air layer drag reduction. A detection technique based on correlation values is implemented to obtain an...

Turbulent flow over liquid-infused superhydrophobic surfaces: An experimental investigation into the drag performance and flow mechanics

Surfaces that induce slip at the wall have been shown to reduce skin friction drag in the turbulent regime. While superhydrophobic and liquid-infused surfaces are capable of drag reduction in turbulent hydrodynamic flows, neither would be feasible in aerodynamic applications due to the added roughness and the minuscule slip lengths created by...

Validatable Shock-Wave/Turbulent Boundary-Layer Interaction over a Compliant Panel

Shock-Wave/Turbulent-Boundary Layer Interactions (SWTBLI) often occur in applications of technological interest. The associated inherent low-frequency unsteadiness dictates the use of Large-Eddy Simulation (LES) approaches to resolve the interaction, which unavoidably implies a very high computational cost. For this reason, no well-resolved long...

Simulation of Two-Dimensional Steady State Boundary Layers Applied to Nonideal Gas Flows

Organic Rankine Cycle (ORC) Power Plants can be of greatimportance in the energy transition as they are suitable for converting wasteheat to power and can utilize renewable energy for their operation. To improvethe efficiency of ORC Power Plants, the physical phenomena inside thesemachines must be understood....

Numerical investigation of the turbulent boundary layer over dimpled surfaces

Dimples are shallow, indented surfaces that attempt to reduce drag in turbulent boundary layer flows. However, the underlying effect of the dimples on the drag is not entirely understood. This thesis sets out to expand our understanding; a numerical investigation of turbulent boundary layer flow over dimpled surfaces is conducted. This research...

Investigating the 3D Flow Structure Downstream of a Fence

In this research the experiments were performed in the water tunnel at the Laboratory for Aero and Hydrodynamics to investigate the 3D flow structure over roughness elements as a model for the flow over urban environment. It represents the first phase in an extended study on the dispersion of pollutants in an urban environment, which process is...

Chevron-shaped protrusions for turbulent drag reduction: Experimental investigation into the drag performance and flow mechanics

In the last decades, the prevailing belief that smooth surfaces offer the lowest drag has been challenged often. Scholars have, for example, introduced rough and modified surfaces to reduce turbulent skin friction. One of the technologies proposed in the literature is an array of chevron-shaped protrusions; however, there is no academic...

Turbulent boundary layers over surfaces with streamwise-preferential permeability: Experimental investigation into the drag and flow mechanics

Turbulent drag is the largest source of fuel consumption in aviation and forms a significant contribution to climate warming. Recent numerical studies have suggested the ability of surfaces with streamwise-preferential permeability to reduce turbulent friction, and a theoretical framework behind the working mechanism has been proposed. This work...

Dimpled channel flows: An experimental investigation into the drag performance of dimpled surfaces in turbulent channel flows

Drag in pipelines is composed almost solely of skin friction drag. The most common technique to achieve drag reduction (DR) is by adding drag-reducing agents. However, in the aerospace industry, various impressive passive drag-reducing techniques have been suggested to reduce skin friction drag in the past decades. Among these techniques,...

On the turbulent drag reduction of a dimpled surface under a pressure gradient

Dimples are spherical indentations applied at a surface that have been found to yield a skin-friction drag reduction within a turbulent boundary layer. Shallow dimples have inherent advantages over traditional flow control techniques that require heavy active systems to be installed or pose maintenance problems. Proven drag-reducing mechanisms...