Turbulent-boundary-layer trailing-edge noise reduction technologies including porous materials

Noise reduction is one of the major challenges to the societal acceptance of wind turbines. Aerodynamic noise sources are the dominant ones, assuming that mechanical noise can be reduced by correct insulation and periodic maintenance of the gearbox and drive train and by adding insulating material in the wind-turbine nacelle. The dominant...

Aerodynamic Noise Reduction with Porous Materials: Aeroacoustics Investigations and Applications

Public annoyances due to noise emission in aviation and wind energy sectors are expected to become more severe in the near future with increasing number of civilian flights and wind turbine installations. Such trend demands for deeper investigations into the noise generation mechanisms and the means to mitigate them. This dissertation addresses...

How Reproducible are Surface Areas Calculated from the BET Equation?

Towards a new salt crystallisation test: Comparison of salt contamination procedure

The RILEM TC 271-ASC is currently developing a new ageing test to assess the<br/>resistance of porous building materials to salt crystallisation. The new test consists of two phases: salt accumulation and damage propagation. This paper focuses on the salt accumulation phase; this phase should promote salt crystallisation close to the evaporative...

Porous Organic Frameworks in Catalysis

This thesis focuses on the development of functional Porous Organic Frameworks (POFs) for various catalytic applications. POF supported molecular catalysts allow to combine the advantages of both homogeneous and heterogeneous catalysts, offering excellent prospects in the quest to heterogenize homogeneous catalysts. The framework tunability of...

On wavemodes at the interface of a fluid and a fluid-saturated poroelastic solid

Pseudo interface waves can exist at the interface of a fluid and a fluid-saturated poroelastic solid. These waves are typically related to the pseudo-Rayleigh pole and the pseudo-Stoneley pole in the complex slowness plane. It is found that each of these two poles can contribute (as a residue) to a full transient wave motion when the...

Molecular simulation strategy for mechanical modeling of amorphous/porous low-dielectric constant materials

We propose an amorphous/porous molecular connection network generation algorithm for simulating the material stiffness of a low-k material (SiOC:H). Based on a given concentration of the basic building blocks, this algorithm will generate an approximate and large amorphous network. The molecular topology is obtained by distributing these blocks...

Guided wave modes in porous cylinders: Theory

The classical theory of wave propagation in elastic cylinders is extended to poro-elastic mandrel modes. The classical theory predicts the existence of undamped L modes and damped C, I, and Z modes. These waves also appear in poro-elastic mandrels, but all of them become damped because of viscous effects. The presence of the Biot slow bulk wave...

Fabrication of in situ ultrathin anodic aluminum oxide layers for nanostructuring on silicon substrate

The authors demonstrate a method for the fabrication of in situ ultrathin porous anodic aluminum oxide layers (aspect ratio<2:1) on Si, which can be directly used as templates for nanodot preparation and for pattern transfer. The regular shape of the aluminum oxide pores is maintained even when the thickness of the aluminum oxide template is...

Impedance Simulation of a Li-Ion Battery with Porous Electrodes and Spherical Li+ Intercalation Particles

We present a semimathematical model for the simulation of the impedance spectra of a rechargeable lithium batteries consisting of porous electrodes with spherical Li+ intercalation particles. The particles are considered to have two distinct homogeneous phases as a result of the intercalation and deintercalation of Li+ during charge and...

Measurements of shock-induced guided and surface acoustic waves along boreholes in poroelastic materials

Acoustic experiments on the propagation of guided waves along water-filled boreholes in water-saturated porous materials are reported. The experiments were conducted using a shock tube technique. An acoustic funnel structure was placed inside the tube just above the sample in order to enhance the excitation of the surface modes. A fast Fourier...

Dispersive surface waves along partially saturated porous media

Numerical results for the velocity and attenuation of surface wave modes in fully permeable liquid/partially saturated porous solid plane interfaces are reported in a broadband of frequencies (100?Hz–1?MHz). A modified Biot theory of poromechanics is implemented which takes into account the interaction between the gas bubbles and both the liquid...

Spatially periodic liquid crystal director field appearing in a photonic crystal template pectroscopy

Active tuning of photonic crystals can be achieved by filling the porous structures with liquid crystals. Here, the director field in macropores was studied by fluorescence confocal polarizing microscopy. For this purpose, the photonic crystal was infiltrated with a glass-forming liquid crystalline polymer, the sample was cooled below the glass...

Molecular-dynamics analysis of the diffusion of molecular hydrogen in all-silica sodalite

In order to investigate the technical feasibility of crystalline porous silicates as hydrogen storage materials, the self-diffusion of molecular hydrogen in all-silica sodalite is modeled using large-scale classical molecular-dynamics simulations employing full lattice flexibility. In the temperature range of 700–1200 K, the diffusion...

Theory of sound propagation in a flow duct lined with annular segments of porous material

A theory is presented to calculate acoustic modes in a circular flow duct lined with porous material. The porous material is divided into annular segments by a rigid structure, which prevents axial sound propagation from one segment into the other. Single modes cannot exist in such a configuration, but it is shown that approximate solutions of...