Wall-normal pores for turbulent drag reduction: Experimental investigation into drag performance and flow mechanics

Flat surfaces with arrays of wall-normal pores called micro-cavity arrays have shown potential to reduce turbulent skin friction drag. Their designs have been inspired by acoustic liners which are sandwich panels consisting of a honeycomb core, a perforated top plate and a solid back sheet used on...

Surrogate models for the characterization of hydrodynamic loads on perforated monopiles

Perforated monopiles show promise in providing a better alternative to the commonly used jacket-like substructures used in intermediate water depths in the range of 30 to 120 m. By introducing perforations near the vicinity of the splash zone the wave loads on the monopile can be mitigated and the fatigue damage reduced, which is the main...

Internalization of targeted microbubbles by endothelial cells and drug delivery by pores and tunnels

Ultrasound insonification of microbubbles can locally enhance drug delivery by increasing the cell membrane permeability. To aid development of a safe and effective therapeutic microbubble, more insight into the microbubble-cell interaction is needed. In this in vitro study we aimed to investigate the initial 3D morphology of the endothelial...

Permeability and Turbulence Over Perforated Plates

We perform direct numerical simulations of turbulent flow at friction Reynolds number Re_τ≈ 500 - 2000 grazing over perforates plates with moderate viscous-scaled orifice diameter d⁺≈ 40 - 160 and analyse the relation between permeability and added drag. Unlike previous studies of turbulent flows over permeable surfaces,...

Perforation of Monopiles to Reduce Hydrodynamic Loads and Enable use in Deep Waters

The offshore wind industry in Europe has experienced significant growth in the past decade, with wind farm development mostly focusing on the shallow area's in the North Sea. Naturally, the market is driven to reduce the Levelised Cost of Electricity (LCoE) to become more competitive with fossil fuels and less dependent on government subsidies....

A novel planar, broadband, high gain lateral wave antenna array for body scanning applications

Three-dimensional body scanning systems are increasingly used in sensitive public areas such as airports. By providing a high resolution image of a person from all sides, it is possible to detect potential metallic, ceramic and explosive threats. For these systems, it is essential to design broadband antennas with a fan beam, highly directional...

Hydrodynamic behaviour of perforated mudmat foundations: Added mass and added damping close to the seabed

Throughout the offshore industry large structures installed on the seabed use mudmats as a foundation to provide in sufficient bearing capacity and stability. Due to their size, the mudmats have a significant influence on the hydrodynamic behaviour and installation requirements. It is proposed to change the design of the mudmats from a near...

Towards Practical Hybrid Laminar Flow Control: Boundary Layer Stability with Suction and Scalability of Pressure Losses across Perforated Sheets

Hybrid laminar flow control (HLFC) reduces skin friction drag, by combining boundary layer suction with pressure gradient tailoring to delay boundary layer transition. This research addresses two key developments required to perform the aerodynamic design of suction-type HLFC components. First, an existing numerical transition prediction tool...

Gardens of Heritage

Gardens of Heritage turns an old warehouse in Chicago into a public park to function as a seedbed for a new handicraft economy.

Multi-storey timber-frame building- modelling the racking stiffness of timber-frame shear-walls

Today, timber structures are receiving attention more and more. Because of the increasing interest in sustainable construction as well as for other reasons, building industry in Europe is (re)-discovering multi-storey timber structures for construction of mid-rise buildings. In this master’s thesis, an analytical calculation method and modelling...

Experimental pressure wave research at NLR for high-speed rail tunnels

Pressure waves, that are generated when a high speed train enters a tiinnel, can cause annoyance to train passengers (rapid pressure fluctuations acting on the train) and for people living near the tunnel (micro-pressure wave). To improve train passenger comfort the effect of various pressure relieving measures (i.e. shafts and porous walls)...

Mechanica van het oprekken van gaten - Analysis of deformation and stresses near cold worked holes

In this report formulas are derived for a description of the deformation and stress fields near holes expanded by cold working. The results are compared with values obtained experimentally and calculated using the finite element method. The model of the material includes linear hardening and a yielding behaviour according to Tresca's criterion....

Lifetime prediction methods for corner cracks at holes

An application of linear elastic fracture mechanics to 3-dimensional crack growth prediction was developed in two phases. In the first phase finite element techniques for accurate stress intensity (S.I.) calculation were evaluated and the Virtual Crack Extension (V.C.E.)-method was selected for further work. In the second phase the process of...

The significance of cladding for fatigue of aluminium alloys in aircraft structures

Flight-simulation tests were carried out on sheet specimens notched "by an open hole (Kt = 2.66). The material was 2024-T3 in three conditions; Alclad, bare and chemically milled. The crack initiation period and the crack propagation period were considerably shorter for the Alclad material. The significance of the cladding, both for constant...