Jan Carmeliet's research while affiliated with ETH Zurich and other places

Publications (205)

Article
Pronounced fingering of the waterfront is observed for in-plane wicking in thin, aligned electrospun fibrous membranes. We hypothesize that a perturbation in capillary pressure triggers the onset of fingering, which grows in a non-local manner based on the waterfront gradient. Vertical and horizontal wicking in thin electrospun membranes of poly(et...
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Pressing problems in urban ventilation and thermal comfort affecting pedestrians related to current urban development and densification are increasingly dealt with from the perspective of climate change adaptation strategies. In recent research efforts, the prime objective is to accurately assess pedestrian-level wind (PLW) environments by using di...
Article
Designing and preparing a fast and easy-to-use immunosensing biochip are of great significance for clinical diagnosis and biomedical research. In particular, sensitive, specific, and early detection of biomarkers in trace samples promotes the application of point-of-care testing (POCT). Here, we demonstrate an all-printed immunosensing biochip with...
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Wetting films can develop in the corners of angular pores under strong wetting conditions. Modeling the dynamics of corner film remains elusive using direct numerical simulations because of the significant scale difference between main meniscus and corner film flow. In this paper, the modified interacting capillary bundle model (ICB), developed in...
Article
Hypothesis Wicking flow in the wale direction of knit fabrics is slowed by capillary pressure minima during the transition at yarn contacts. The characteristic pore structure of yarns leads to an unfavorable free energy evolution and is the cause of these minima. Experiments Time-resolved synchrotron tomographic microscopy is employed to study the...
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In this work, a numerical model for isothermal liquid-vapor phase change (evaporation) of the two-component air-water system is proposed based on the pseudopotential lattice Boltzmann method. Through the Chapman-Enskog multiscale analysis, we show that the model can correctly recover the macroscopic governing equations of the multicomponent multiph...
Article
The spontaneous imbibition of a liquid within porous media, known as wicking, can display uncommon features in textiles and yarns. Yarns exhibited step-wise wicking dynamics not captured by current models. Hypothesis Wicking dynamics in yarns not only depend on inter-fiber pore filling, but are mainly determined by the pore-to-pore transition proc...
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The classical D 2-Law states that the square of the droplet diameter decreases linearly with time during its evaporation process, i.e., D 2 (t) = D 2 0 −Kt, where D 0 is the droplet initial diameter and K is the evaporation constant. Though the law has been widely verified by experiments, considerable deviations are observed in many cases. In this...
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Green walls are considered a sustainable and environmental technology for improving the local urban microclimate. The presented wind tunnel measurements reveal the coupling effect of aerodynamic and thermal resistance of green walls in flat and steep street canyons in a simplified urban neighborhood model. The building and ground surfaces are set t...
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Plants modify the climate and provide natural cooling through transpiration. However, plant response is not only dependent on the atmospheric evaporative demand due to the combined effects of wind speed, air temperature, humidity, and solar radiation, but is also dependent on the water transport within the plant leaf-xylem-root system. These intera...
Article
Vapor sorption in hygroscopic porous materials is accompanied by latent heat release/storage, which can influence indoor thermal comfort and building heating and cooling energy consumption. There is a need to better understand the coupled vapor and heat transport during adsorption and desorption. In this study, longitudinal spruce samples are expos...
Article
Porous media play important roles in a wide range of scientific and engineering problems. Recently, with their increasing application in energy conversion and storage devices, such as fuel cells, batteries and supercapacitors, it has been realized that transport processes and reactions occurring in the pores and at the interfaces of different const...
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The moisture-induced shape memory effect (SME) is one of the most intriguing phenomena of wood, where wood can stably retain a certain deformed shape and, upon moisture sorption, can recover the original shape. Despite the long history of wood utilization, the SME is still not fully understood. Combining molecular dynamics (MD) and finite-element (...
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Due to the need to preserve the façades of valuable historical buildings, internal thermal insulation is often the only measure for energy retrofitting for such class of buildings. However, internal thermal insulation may lead to moisture damage risks. In this study, the influence of seven parameters, namely water absorption coefficient and diffusi...
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Wood is known to swell substantially during moisture adsorption and shrink during desorption. These deformations may lead to wood damage in the form of cracking and disjoining of wooden components in e.g. floor or windows. Two swelling mechanisms may be distinguished: reversible swelling/shrinkage and moisture-induced shape memory effect. In the la...
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Drying at macroscale shows a first drying period with constant drying rate followed by second drying period showing a receding moisture front, phenomena that can be tailored upon need. In order to study the drying of materials, we present a new hybrid computational method, where the dynamics of the liquid-vapor interfaces is modelled by lattice Bol...
Article
To design energy access solutions for rural households in developing countries it is important to have an accurate estimation of what their electricity consumption is. Studies reveal that they mainly use electricity to meet their lighting needs, as they cannot afford high power-consuming appliances. However, the scarce data availability and modelin...
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Parts of the building envelope that frequently receive high amounts of rain are usually exposed to a higher risk of deterioration due to moisture. Determination of such locations can thus help with the assessment of moisture-induced damage risks. This study performs computational fluid dynamics (CFD) simulations of wind-driven rain (WDR) on the Par...
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Natural convection arising over vertical and horizontal heated flat surfaces is one of the most ubiquitous flows at a range of spatiotemporal scales. Despite significant developments over more than a century contributing to our fundamental understanding of heat transfer in natural convection boundary layers, certain “hidden” characteristics of thes...
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Drying of porous media is governed by a combination of evaporation and movement of the liquid phase within the porous structure. Contact angle hysteresis induced by surface roughness is shown to influence multi-phase flows, such as contact line motion of droplet, phase distribution during drainage and coffee ring formed after droplet drying in cons...
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Intermolecular interactions at the fiber-matrix interface strongly affect the hygromechanical behavior and overall mechanical performance of hydrophilic cellulosic nanocomposites. The mechanics of a model interface consisting of cellulose and galactoglucomannan, inspired by the natural material wood, is investigated by molecular simulations over th...
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With rapid urbanization, population growth and anthropogenic activities, an increasing number of major cities across the globe are facing severe urban heat islands (UHI). UHI can cause complex impacts on the urban environment and human health, and it may bring more severe effects under heatwave (HW) conditions. In this paper, a holistic review is c...
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Despite the thousands of years of wood utilization, the mechanisms of wood hygromechanics remain barely elucidated, owing to the nanoscopic system size and highly coupled physics. This study uses molecular dynamics simulations to systematically characterize wood polymers, their mixtures, interface, and composites, yielding an unprecedented micromec...
Article
Particle image velocimetry (PIV) is commonly used to measure multiple field-of-views (FOVs) of the flow in large urban domains, performed in wind tunnels using an array of cameras located at fixed positions or a single camera setup that traverses during the measurements. With respect to the large amount of data produced in this type of measurement,...
Article
In light of globally increasing temperatures, accentuated in cities by the urban heat island effect, urban planners and designers are looking for new, quantitative methods to assess the performance of their designs in terms of ecosystem services provided by vegetation. Among these ecosystem services, improved microclimate conditions are particularl...
Article
The present wind tunnel particle image velocimetry (PIV) measurements document flows around flat and steep street canyons subject to thermal conditions at different levels, ranging from the Richardson number of 0.31 to 2.07. A steepness ratio, that is, the ratio of windward and leeward building heights, is proposed to characterise the geometrical i...
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In this work, a hybrid method coupling a pseudo-potential lattice Boltzmann model (LBM) and a pore network model (PNM) to simulate drying in porous media is proposed. Based on the watershed method, the porous medium is firstly decomposed into pore regions. According to the liquid–vapor phase distribution at a given time, the pore regions are furthe...
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This paper investigates modeling methods with thermal network representation under the scope of the optimal design and operation of Distributed Multi-Energy System (D-MES). Two modeling approaches are compared: A Mixed‐Integer Linear Programming (MILP) optimization model and a district heating network (DHN) simulation model. The MILP model was deve...
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Buoyancy-driven flows on a horizontal plate subject to a ramp heating of finite time are studied in this paper. The dynamics of the thermal boundary layer and the subsequent starting plume on the heated horizontal plate are revealed and the scaling laws for different scenarios and regimes are obtained using a scaling analysis, which are further ver...
Article
What are the mechanisms at play in the spontaneous imbibition dynamics in polyethylene terephthalate filament yarns at pore scale? Processes at pore scale such as waiting times between the filling of two neighboring pores, as observed in special irregular porous media, like yarns, may overrule the predicted behavior by well-known laws such as Washb...
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The evolution of frictional strength during stick-slip dynamics of a fault system is key to understanding earthquake nucleation and rupture patterns. In mature faults, granular gouge is produced by wear, comminution or fragmentation during tectonic movements. In this work, we introduce a fragmentation model in the simulation of a sheared granular f...
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This paper presents an analysis of the path towards a clean energy transition in rural areas, from the time that households do not have electricity access from any source, to when they get access to the national electricity; considering the intermediate access to an off-grid renewable technology, as well as the post-electrification years. For this,...
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Increasing urban tree cover is an often proposed mitigation strategy against urban heat as trees are expected to cool cities through evapotranspiration and shade provision. However, trees also modify wind flow and urban aerodynamic roughness, which can potentially limit heat dissipation. Existing studies show a varying cooling potential of urban tr...
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Drying of colloidal suspension towards the exploitation of the resultant nanoparticle deposition has been applied in different research and engineering fields. Recent experimental studies have shown that neck-based thermal structure (NTS) by colloidal nanoparticle deposition between microsize filler particle configuration (FPC) can significantly en...
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In this study, a holistic energy, economic and environmental assessment was performed on a prosumer-based district heating system, including scenarios with varying district size, retrofitting stages and system configurations. A modeling framework was built which comprises a thermal network design and simulation model; a building energy demand model...
Article
Spontaneous imbibition in an angular tube with corner films is a fundamental problem in many scientific and engineering processes. In this study, a modified interacting capillary bundle model is developed to describe the liquid imbibition dynamics in a square tube with corner films. The square tube is decomposed into several interacting subcapillar...
Preprint
Dense granular systems subjected to an imposed shear stress undergo stick-slip dynamics with systematic patterns of dilation-compaction. During each stick phase, as the frictional strength builds up, the granular system dilates to accommodate shear strain, developing stronger force networks. During each slip event, when the stored energy is release...
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Solar drying is regarded as a less reliable process compared to continuous hot-air drying due to the intermittency of solar radiation. This problem is mitigated by equipping solar dryers with thermal storage, dehumidifier units, or auxiliary heating that enhances drying continuity during night time. In this study, we combine a mechanistic fruit dry...
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Crystalline cellulose, the most abundant natural polymer on earth, features exceptional physical and mechanical properties. Using atomistic simulation, this study reports the mechanical behavior of cellulose-cellulose nanocrystal hydrophilic interface and systematically examines the impact of loading direction, interfacial moisture, misalignment an...
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Thermal management is one of the major challenges facing the development of three-dimensional (3D) chip stacks. Recently, experimental studies have shown that neck-based thermal structure (NTS) between chip layers formed by drying of colloidal suspension in cavity filled with micro-size particles can improve the vertical heat conduction threefold....
Preprint
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As cities and their population are subjected to climate change and urban heat islands, it is paramount to have the means to understand the local urban climate and propose mitigation measures, especially at neighbourhood, local and building scales. A framework is presented, where the urban climate is studied by coupling a meteorological model to a b...
Article
Convective drying of fruits leads to microstructural changes within the material as a result of moisture removal. In this study, an upscaling approach is developed to understand and identify the relation between the drying kinetics and the resulting microstructural changes of apple fruit, including shrinkage of cells without membrane breakage (free...
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Internal insulation of masonry walls may significantly increase the decay risk of embedded wooden beams due to lower temperature and consequently lower drying potential in retrofitted existing walls. Since high moisture contents will affect performance and service life of wood, the assessment of moisture-related damage risks in wooden beam-ends in...
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Nanoparticle deposition by drying of colloidal suspension in thin micro-porous architectures has attracted a lot of attention in scientific research as well as industrial applications. However, the underlying mechanisms of such three-dimensional (3D) deposition are not yet fully revealed due to the complexity of the co-occurring processes of two-ph...
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The Urban Heat Island Effect describes the phenomenon that urban areas are typically warmer than the nearby rural areas, as the presence of the city causes an increase in air temperature. Increased temperatures in urban environments lead to increased discomfort, health problems, and higher cooling demands. It is therefore essential to be able to pr...
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Sorption hysteresis in nanoporous polymer is an intriguing phenomenon that involves coupling between sorption and deformation. Based on the mechanism revealed at the microscopic level using molecular simulation, a poromechanical model is developed capturing all relevant physics and yielding a quantitative description. In this model, the coupling be...
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Hydrodynamic Printing In their Communication on page 14234, M. Su, Y. Song et al. describe a non‐lithography hydrodynamic printing strategy for preparing micro/nanostructures on curved surfaces. This strategy provides a general platform for curved optoelectronics.
Article
Hydrodynamisches Drucken In ihrer Zuschrift auf S. 14340 beschreiben M. Su, Y. Song et al. eine Strategie für das hydrodynamische Drucken von Mikro/Nanostrukturen auf gekrümmten Oberflächen. Die Strategie bietet eine allgemeine Plattform für die Fertigung gekrümmter Optoelektronik.
Preprint
Convective drying of fruits leads to microstructural changes within the material as a result of moisture removal. In this study, an upscaling approach is developed to understand and identify the relation between the drying kinetics and the resulting microstructural changes of apple fruit, including shrinkage of cells without membrane breakage (free...
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Full-text available
Urban areas are increasingly impacted by the urban heat island effect, especially during heat waves. In the context of improving energy efficiency in buildings, passive and energy-efficient cooling methods are needed for reducing indoor heat stress and lowering building energy consumption during heat waves. In this study, a whole building simulatio...
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A molecular model of an all-cellulose nanocomposite, with an amorphous cellulose matrix reinforced by cellulose nanocrystals, is built to study the role of cellulose nanocrystal (CN) as a nanofiller in the coupled behavior between sorption and deformation. We find two competitive mechanisms. The first mechanism is the reinforcing effect through CN-...
Article
In this paper, different pore network models to simulate single-phase flow in porous media are built and their accuracy is evaluated. In addition to the conventional pore network model (CPNM) which consists of regular pore bodies and throat bonds, three improved pore network models (IPNMs) are developed allowing to better describing the real pore a...
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A key issue of micro‐nano devices will be how to integrate micro/nanostructures with specified chemical component onto various curved surfaces. Here, we achieve hydrodynamic printing micro/nanostructures on three‐dimensional curved surfaces via the combination strategy from the template‐induced hydrodynamic printing and self‐assembly of nanoparticl...
Article
Curveball: A non‐lithography hydrodynamic printing strategy is proposed for preparing micro/nanostructures on three‐dimensional curved surfaces. A capillary pumped function between the template and curved substrates assembles nanoparticles on curved surfaces at the resolution of single nanoparticles. The strategy provides a general platform for opt...
Article
The energy strategies used to plan future emissions reductions typically have separate strategies for decarbonisation of the transport and building sectors. However, the advent and diffusion of alternative fuel vehicle technologies could result in vehicle transport becoming a major energy load in urban energy systems in addition to heating and elec...