Biomimetic research indicates that many phenomena regarding wettability in nature, such as the self-cleaning effect on a lotus leaf and cicada wing, the anisotropic dewetting behavior on a rice leaf, and striking superhydrophobic force provided by a water strider's leg, are all related to the unique micro- and nanostructures on the surfaces. It gives us much inspiration to realize special wettability on functional surfaces through the cooperation between the chemical composition and the surface micro- and nanostructures, which may bring great advantages in a wide variety of applications in daily life, industry, and agriculture. This Account reviews recent progress in these aspects.

/pdf/bioinspired-surfaces-with-special-wettability-epailt8nha.pdf

Bioinspired surfaces with special wettability

During recent years, major progress has been made in the understanding of the adsorption, pore condensation and hysteresis behavior of fluids in novel ordered nanoporous materials with well defined pore structure. This has led to major advances in the structural characterization by physical adsorption, also because of the development and availability of advanced theoretical procedures based on statistical mechanics (e.g., density functional theory, molecular simulation) which allows to describe adsorption and phase behavior of fluids in pores on a molecular level. Very recent improvements allow even to take into account surface geometrical in-homogeneity of the pore walls However, there are still many open questions concerning the structural characterization of more complex porous systems. Important aspects of the major underlying mechanisms associated with the adsorption, pore condensation and hysteresis behavior of fluids in micro-mesoporous materials are reviewed and their significance for advanced physical adsorption characterization is discussed.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/cite.201000064

Physical Adsorption Characterization of Nanoporous Materials

https://cmapspublic3.ihmc.us/rid=1LTYVNQH7-27GSQ6R-2963/science.pdf

Stimuli-responsive polymers: Biomedical applications and challenges for clinical translation ☆

Although Nature has always been a common source of inspiration in the development of artificial materials, only recently has the ability of man-made materials to produce complex three-dimensional (3D) structures from two-dimensional sheets been explored. Here we present a new approach to the self-shaping of soft matter that mimics fibrous plant tissues by exploiting small-scale variations in the internal stresses to form three-dimensional morphologies. We design single-layer hydrogel sheets with chemically distinct, fibre-like regions that exhibit differential shrinkage and elastic moduli under the application of external stimulus. Using a planar-to-helical three-dimensional shape transformation as an example, we explore the relation between the internal architecture of the sheets and their transition to cylindrical and conical helices with specific structural characteristics. The ability to engineer multiple three-dimensional shape transformations determined by small-scale patterns in a hydrogel sheet represents a promising step in the development of programmable soft matter.

/pdf/three-dimensional-shape-transformations-of-hydrogel-sheets-3xf3piw2yn.pdf

Three-dimensional shape transformations of hydrogel sheets induced by small-scale modulation of internal stresses

https://spectrum.library.concordia.ca/973679/1/DJS-JKO-KM_-_PPS_2011_-_ATRP_Bio_review_Revision_fnal.pdf

ATRP in the design of functional materials for biomedical applications

Experiment, Theory and Application

In spite of recent advances in LES methods, RANS based jet noise prediction models appear to be the only realistic, near term, approach for the development of a jet noise prediction procedure that is applicable to chevron nozzle flows, or other advanced nozzle designs. The present paper describes the application of such a model to a series of chevron nozzle flows and the model predictions are compared with experimental data. It is shown that the chevr ons affect t he flow in two important ways. The f irst effect is that the axial vortices cause a very rapid increase in the width of the mixing layer. This process, in effect, leads to a local im balance between the turb ulence and the mean flow, a reduction i n the turbulence production, and an overall reduction in the peak turbulence level, thus contributing to a noise reduction at the lower frequencies. The second is more complex and appears to involve an interaction between the axial vortices and the jet tur bulence that causes more of the high frequency noise from this region to be radiated to the far field. The strength of this new noise source appears to scale with the strength of the axial vortices.

Noise Predictions for Chevron Nozzle Flows

None of the standard turbulence models usually found in CFD codes will accurately predict the mixing in even simple axisymmetric jets, and none of the turbulence model modifications that have been proposed to resolve this problem are accurate for more complex jet flows. Because of this, the turbulence modeling requirements for coaxial and chevron nozzle flows are not well understood at present. In this paper, a simple zonal model is used to identify these turbulence modeling requirements. In the course of this work, it was discovered that coaxial jet flows could be very unstable, leading to strongly asymmetrical jet development for small distortions of nominally axisymmetric geometries.

Numerical Modeling Requirements for Coaxial and Chevron Nozzle Flows

Several experimental, computational and theoretical results devoted to turbulence jet noise are described. All these results were obtained at CIAM in collaboration with the Boeing Company. The selected topics are combined and described from a single point of view. In spite of the many publications in the classical literature devoted to jet noise, many jet noise problems are not completely solved, and most current jet noise prediction methods are still highly empirical and rely heavily on an existing experimental data base. At the same time, many of the available experimental results are not fully reliable and some are even contradictory. The goal of this paper is, therefore, to explore and discuss some of the possibilities and limitations of classical aeroacoustics methods.

On the prediction of turbulent jet noise using traditional aeroacoustic methods

Systems and methods for passively directing aircraft engine nozzle flow are disclosed. One system includes an aircraft nozzle attachable to an aircraft turbofan engine, with the nozzle including a first flow path wall bounding a first flow path and being positioned to receive engine exhaust products, and a second flow path wall bounding a second flow path and being positioned to receive engine bypass air. The first flow path wall is positioned between the first and second flow paths, and the second flow path wall is positioned between the second flow path and an ambient air flow path. Multiple flow passages can be positioned in at least one of the first and second flow path walls to passively direct gas from a corresponding flow path within the flow path wall through the flow path wall to a corresponding flow path external to the flow path wall. Neighboring flow passages can have neighboring circumferentially-extending and circumferentially-spaced exit openings positioned at an interface with the corresponding flow path external to the flow path wall.

D. A. Lyubimov

Papers

Experiment, Theory and Application

Noise Predictions for Chevron Nozzle Flows

Numerical Modeling Requirements for Coaxial and Chevron Nozzle Flows

On the prediction of turbulent jet noise using traditional aeroacoustic methods

Systems and methods for passively directing aircraft engine nozzle flows