Alexandros Terzis

Alexandros Terzis
Technion - Israel Institute of Technology | technion · Faculty of Aerospace Engineering

D.Sc.

About

63
Publications
23,908
Reads
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759
Citations
Citations since 2016
40 Research Items
650 Citations
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2016201720182019202020212022020406080100120140
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Introduction
My research is in the area of thermofluids and interfaces, and spans a wide breadth of activities in the fields of fluid mechanics, thermodynamics and transport phenomena, with a host of applications and a strong link to fundamentals. The focus is on understanding the related physics across scales (submicron/meso to macro), and in complex multi-phase media, and employing this knowledge to the development of interdisciplinary research that can address crucial scientific challenges.
Additional affiliations
September 2020 - present
Technion - Israel Institute of Technology
Position
  • Professor (Assistant)
April 2019 - July 2020
Stanford University
Position
  • Research Associate
March 2016 - April 2019
Universität Stuttgart
Position
  • PostDoc Position
Education
November 2009 - May 2014
École Polytechnique Fédérale de Lausanne
Field of study
  • Mechanical Engineering
October 2008 - September 2009
Cranfield University
Field of study
  • Gas Turbine Technology
October 2002 - July 2008
Aristotle University of Thessaloniki
Field of study
  • Mechanical Engineering

Publications

Publications (63)
Article
Full-text available
Flow visualization is one of many available tools in experimental fluid mechanics and is used from the primary stages of fluid mechanics research in order to identify the physical sizes and locations of the flow features under consideration. Most of the fluids used in engineering applications are transparent (water, air, etc) and flow visualization...
Article
Full-text available
Experimental heat transfer measurements are used in a wide range of fields, for example to validate new cooling concepts in turbomachinery, to assess the performances of heat exchangers, and to provide data for numerical simulations. A particular challenge is posed by complex geometries, where the heat transfer coefficients cannot be determined wit...
Article
Many engineering technologies such as electronic cooling and thermal desalination exemplify the enhancement of evaporation and boiling heat transfer by surface modification. Nevertheless, the core parameters of heat transfer such as critical heat flux and heat transfer coefficient are associated with surface wettability and morphology. Herein, for...
Article
Full-text available
Turbulent channel flow with a porous wall is investigated using direct numerical simulation, where the porous media domain consists of regular or random circular cylinder arrays. We compare the statistics and structure of the mean flow and turbulence in the channel flow with a bulk Reynolds number of 2500 and two porosities (φ=0.6 and 0.8) for the...
Article
Heat transfer measurements are required in a wide range of fields, for example to validate new cooling concepts in turbomachinery, to assess the performances of heat exchangers, and to provide data for numerical simulations. Thereby transient methods are often applied for local heat transfer resolution. A particular challenge is posed by complex fl...
Article
The double-wall cooling systems with internal jet impingements and external film cooling are greatly applicable in modern turbine blades, providing enhanced cooling capabilities compared to the conventional passage cooling. This paper presents experimental and numerical results of flow and heat transfer characteristics of a double-wall cooling conf...
Article
Full-text available
Transient heat generation during guest adsorption and host–guest interactions is a natural phenomenon in metal–organic framework (MOF) chemistry. However, in situ tracking of such MOF released heat is an insufficiently researched field due to the fast heat dissipation to the surroundings. Herein, a facile capillary‐driven liquid‐imbibition approach...
Article
Full-text available
A facile capillary‐driven liquid‐imbibition approach is developed in article number 2006980 by Guang Yang, Roland A. Fischer, and co‐workers for in situ tracking of transient heat release at the wetting front of surface‐mounted metal–organic frameworks (SURMOFs) on cellulosic fiber papers. As an advancement to the state‐of‐the‐art in trace‐solvent...
Article
Full-text available
Turbulence transportation across permeable interfaces is investigated using direct numerical simulation, and the connection between the turbulent surface flow and the pore flow is explored. The porous media domain is constructed with an in-line arranged circular cylinder array. The effects of Reynolds number and porosity are also investigated by co...
Article
Full-text available
Modeling coupled systems of free flow adjacent to a porous medium by means of fully resolved Navier–Stokes equations is limited by the immense computational cost and is thus only feasible for relatively small domains. Coupled, hybrid-dimensional models can be much more efficient by simplifying the porous domain, e.g., in terms of a pore-network mod...
Article
Joule heating in isotachophoresis (ITP) can limit minimum assay times and efforts to scale up processed sample volumes. Despite its significance, the dynamics of Joule heating on spatiotemporal temperature fields in ITP systems have not been investigated. We here present novel measurements of spatiotemporal temperature and electromigration fields i...
Article
Full-text available
The productivity of continuously cycled atmospheric water harvesting methods using metal-organic frameworks (MOFs) has been limited by a lack of scalable designs and robust MOF form factors compatible with rapid heat and mass transport. Explored here is the fluidization of MOF-801 powder in its native particulate form as a water vapor sorption unit...
Article
Full-text available
The mechanism of dynamic wetting and the fluid dynamics during the onset of droplet mobilization driven by a microchannel flow are not clearly understood. In this work, we use microparticle tracking velocimetry to visualize the velocity distribution inside the droplet both prior to and during mobilization. Time-averaged and instantaneous velocity v...
Article
Full-text available
We present both experimental results and numerical simulations of the fluid dynamics of a droplet pinned to the hydrophobic surfaces of a confined microfluidic channel, as a result of contact angle hysteresis. Internal circulations in the droplet are observed and quantified using micro-particle image velocimetry (µPIV). As the channel inlet velocit...
Preprint
Full-text available
Modeling coupled systems of free flow adjacent to a porous medium by means of fully resolved Navier-Stokes equations is limited by the immense computational cost and is thus only feasible for relatively small domains. Model reduction allows to decrease a model's complexity while maintaining an acceptable degree of accuracy. Starting from a fully re...
Poster
Spontaneous imbibition in cellulosic materials is an expanding field of research due to the direct applicability in paper-based microfluidics. Here, it is shown experimentally, using simultaneous thermal (IR) and optical (CCD) imaging, that the temperature at the wetting front during capillary filling of paper is temporarily increased, even if the...
Article
Full-text available
A channel flow coupled with a transversal stream through porous structures is investigated numerically in this study. Velocity profiles are obtained on the pore-scale and averaged to the macro-scale in order to evaluate the validity of the Beavers-Joseph interface condition. For this purpose, different ratios between the velocity at the inlet of th...
Article
The rapid implementation of Selective-Catalytic-Reduction (SCR) technologies into light passenger and commercial vehicles, led to the omission of fundamental research creating several reliability issues that are largely related to the research field of droplet dynamics. In this study, the splashing behavior of an AdBlue droplet impacting onto thin...
Article
This study examines experimentally the hydrodynamic interaction between a regular porous medium and an adjacent free-flow channel at low Reynolds numbers (Re < 1). The porous medium consists of evenly spaced micro-structured rectangular pillars arranged in a uniform pattern, while the free-flow channel features a rectangular cross-sectional area. T...
Article
Full-text available
The impact of solid bodies on the free surface of liquid pools is involved in many practical applications—such as bullets and air-to-sea anti-torpedo defense systems, or the water entry of athletes in water sports—aimed at improving the performance through a control of cavity dynamics. This work reports an experimental investigation of the impact o...
Conference Paper
Full-text available
It is quite well-known that by altering the surface wetting characteristics of a solid sphere impacting on a deep water pool, the formation and evolution of underwater cavity in its wake can be controlled. The video shows the results from a preliminary study on impact of a linear array of hydrophilic (H) and superhydrophobic (SH) spheres on a deep...
Article
This study demonstrates the capability of the DFT formalism to predict contact angles and density profiles of model fluids and of real substance in good quantitative agreement to molecular simulations and to experimental data. The DFT problem is written in cylindrical coordinates and the solid-fluid interactions are defined as external potentials t...
Article
Full-text available
Understanding the mobilisation of trapped globules of non-wetting phase during two-phase flow has been the aim of numerous studies. However, the driving forces for the mobilisation of the trapped phases are still not well understood. Also, there is little information about what happens within a globule before, at the onset and during mobilization....
Article
Full-text available
In our recent paper, Yang et al. Transp Porous Med (2018) 122:145.10.1007/s11242-017-0995-9, the correct Nusselt numbers in Sections “3.2 Grid Independence Test” and “4.7 Heat Transfer in the Porous Structure” should be the shown values multiplied by 4. This has been a post-processing mistake when producing the figures. This leads to the following...
Article
Full-text available
This study investigates numerically the turbulent flow and heat transfer characteristics of a T-junction mixing, where a porous media flow is vertically discharged in a 3D fully developed channel flow. The fluid equations for the porous medium are solved in a pore structure level using an Speziale, Sarkar and Gatski turbulence model and validated w...
Article
We present the potential of a quantitative temperature-based diagnostic approach for paper-based microfluidics, extending the work of Terzis et al. (J Colloid Interface Sci 504:751–757, 2017) which demonstrated a significant heat release at the liquid front during capillary-driven flows in cellulosic materials. Here, we investigate the applicabilit...
Article
The injection of urea-water-solution sprays in the exhaust pipe of modern diesel engines eliminates NOx emissions in a very great extent. However, as water evaporates from the solution, urea is crystallized and causes wall-deposit formations hindering the performance of selective-catalytic-reaction. In this study, the crystallization of urea from a...
Article
The objective of this study is to determine the Lifshitz–van der Waals/Acid–Base (LW/AB) surface energy components of urea–water solutions (UWS) for different urea mass fractions. The surface energy parameters are evaluated by ring tensiometry and contact angle measurements of sessile drops placed onto pre-determined solid substrates. Therefore, th...
Article
Full-text available
It is reported that temperature rises at wetting front during water infiltration into soil. The temperature goes back to the background value after passage of water front. Different explanations have been provided for source of energy causing temperature spike. Some have contributed it to heat of condensation released due to condensation of vapor o...
Article
Full-text available
The present paper investigates experimentally the impact dynamics of crown-type splashing for miscible two- and one-component droplet wall–film interactions over a range of Weber numbers and dimensionless film thicknesses. The splashing outcome is parametrised in terms of a set of quantifiable parameters, such as crown height, top and base diameter...
Article
Spontaneous imbibition in cellulosic materials is an expanding field of research due to the direct applicability in paper-based microfluidics. Here, we show experimentally, using simultaneous thermal and optical imaging that the temperature at the wetting front during capillary filling of paper is temporarily increased, even if the imbibed fluid an...
Conference Paper
Full-text available
The phenomenon of a single drop impact onto a thin liquid film (e.g. wall-film) is encountered over a wide range of natural and engineering applications. Among different drop impact morphologies, splashing has drawn great attention over the last decades due to its relatively complex morphology that is characterised by liquid fingers at the upper cr...
Article
Full-text available
The correspondence between local fluid flow structures and convective heat transfer is a fundamental aspect that is not yet fully understood for multiple jet impingement. Therefore, flow field and heat transfer experiments are separately performed investigating mutual--jet interactions exposed in a self-gained crossflow. The measurements are taken...
Article
Integrally cast turbine airfoils with wall-integrated cooling cavities are greatly applicable in modern turbines providing enhanced heat exchange capabilities compared to conventional cooling passages. In such arrangements, narrow impingement channels can be formed where the generated crossflow is an important design parameter for the achievement o...
Article
This paper examines the applicability of a triple layer of thermochromic liquid crystals (TLCs) for the determination of local heat transfer coefficients using the transient liquid crystal (LC) technique. The experiments were carried out in a narrow impingement channel , typically used for turbine blade cooling applications. Three types of narrow b...
Article
Transient heat transfer experiments typically employ thermochromic liquid crystals to temporally map surface temperatures. The desired heat transfer coefficient is then calculated from the solution of Fourier’s 1D transient heat conduction equation which is set to model the wall temperature at the solid–fluid interface. However, the experimental co...
Conference Paper
Full-text available
The present study describes an experimental investigation into narrow impingement cooling channels with divergent geometries. The following analysis aims to clarify the influence that this particular form factor exerts on the heat transfer distribution, as well as on the traverse crossflow of the cooling passages. The research is based on the outco...
Article
Full-text available
This paper demonstrates that the impact of nanosecond pulsed dielectric barrier discharge (ns-DBD) actuators on the structure of the boundary layer can be investigated using quantitative convective heat transfer measurements. For the experiments, the flow over a flat plate with a C4 leading edge thickness distribution was examined at low speed inco...
Conference Paper
Full-text available
This paper examines the applicability of a triple layer of thermochromic liquid crystals on the evaluation of local heat transfer coefficients using the transient liquid crystal measurement technique. The experiments were carried out in a narrow impingement cooling channel typically found in turbine airfoils. Narrow-band liquid crystals of 35°C, 38...
Article
Full-text available
In modern turbine airfoils, narrow impingement cooling channels can be formed in a double-wall configuration. In these wall-integrated cooling cavities, the generated crossflow is one of the most important design factors, and hence, the number of impingement holes included in a channel. This study examines experimentally the influence of the number...
Article
The development of integrally cast turbine airfoils allows the production of narrow impingement channels in a double-wall configuration, where the coolant is practically injected within the wall of the airfoil providing increased heat transfer capabilities. This study examines the cooling performance of narrow impingement channels with varying jet...
Article
The present study demonstrates an alternative approach for describing fluid flow characteristics very close to the wall, using locally resolved convective heat transfer experiments. Heat transfer coefficients on the base surface and around a surface mounted vortex generator of delta-wing shape design, are evaluated with the transient liquid crystal...
Article
The current capabilities of the foundry industry allow the production of integrally cast turbine airfoils. Impingement cooling effectiveness can be then further increased due to the manufacturing feasibility of narrow impingement cavities in a double-wall configuration. This study examines experimentally, using the transient liquid crystal techniqu...
Article
Full-text available
In many engineering applications, heat transfer enhancement techniques are of vital importance in order to ensure reliable thermal designs of convective heat transfer applications. This study examines experimentally the heat transfer characteristics on the base plate around various surface mounted obstacles. Local convection coefficients are evalua...
Article
This study examines experimentally the cooling performance of narrow impingement channels as could be cast-in in modern turbine airfoils. Full surface heat transfer coefficients are evaluated for the target plate and the sidewalls of the channels using the transient liquid crystal technique. Several narrow impingement channel geometries, consisting...
Article
Impingement cooling effectiveness of gas turbine vanes and blades can be further increased due to the manufacturing feasibility of integrally cast airfoils which can provide narrow impingement cooling cavities. This study examines experimentally using the transient liquid crystal technique, and numerically using a commercial CFD package, the heat t...
Article
The heat transfer characteristics of a fully confined impingement jet are experimentally and numerically evaluated. Full surface heat transfer coefficient distributions are obtained for the target and impingement plate of the model using the transient liquid crystal technique and a commercial CFD solver. The confined box consists of a single round...
Article
The transient liquid crystal technique is widely used for impingement heat transfer experiments. Additionally, due to the difficulty of producing pure temperature steps in the flow, many authors assumed the fluid temperature evolution as a series of step changes using Duhamel's superposition theorem. However, for small impingement configurations wh...
Conference Paper
This study examines experimentally the cooling performance of integrally cast impingement cooling channels which provide increased heat transfer area compared to traditional impingement configurations. For the evaluation of the heat transfer coefficient, the transient liquid crystal method was used. Full surface heat transfer coefficient distributi...
Article
Full-text available
This study examines experimentally the effect of stators on the performance and heat transfer characteristics of small axial cooling fans. A single fan impeller, followed by nine stator blades in the case of a complete stage, was used for all the experimental configurations. Performance measurements were carried out in a constant speed stage perfor...
Article
Full-text available
This investigation examines experimentally the behavior of swirled jets produced by axial flow fans blowing into a crossflow at low velocity ratios. The main difference with non-swirl cases is an asymmetry of the dominant kidney vortex and a slight distortion of the jet trace downstream of the injection hole. The effect of jet rotation at relativel...
Conference Paper
Full-text available
In this investigation impact ice strength is experimentally evaluated in terms of fracture energy and fracture toughness using equations based on Linear Elastic Fracture Mechanics (LEFM). Experiments carried out in a crack opening mode-I test rig capable to work with the icing tunnel in operation so that the temperature and residual strain distribu...