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Professor, Head of the department, Mechanical Engineering, University of Canterbury.
This paper presents a numerical method to address function estimation problems in inverse heat transfer problems using parameter estimation approach without prior information on the functional form of the variable to be estimated. Using an inverse analysis, the functional form of a time-dependent heat transfer coefficient is estimated efficiently and accurately. The functional form of the heat transfer coefficient is assumed unknown and the inverse heat transfer problem should be treated using a function estimation approach by solving sensitivity and adjoint problems during the minimization process. Based on proposing a new sensitivity matrix, however, the functional form can be estimated in an accurate and very efficient manner using a parameter estimation approach without the need for solving the sensitivity and adjoint problems and imposing extra computational cost, mathematical complexity, and implementation efforts. In the proposed sensitivity analysis scheme, all sensitivity coefficients can be computed in only one direct problem solution at each iteration. In this inverse heat transfer problem, the body shape is irregular and meshed using a body-fitted grid generation method. The direct heat conduction problem is solved using the finite-difference method. The steepest-descent method is used as a minimization algorithm to minimize the defined objective function and the termination of the minimization process is carried out based on the discrepancy principle. A test case with three different functional forms and two different measurement errors is considered to show the accuracy and efficiency of the used inverse analysis.
Farzad Mohebbi; Mathieu Sellier. Estimation of Functional Form of Time-Dependent Heat Transfer Coefficient Using an Accurate and Robust Parameter Estimation Approach: An Inverse Analysis. Energies 2021, 14, 5073 .
AMA StyleFarzad Mohebbi, Mathieu Sellier. Estimation of Functional Form of Time-Dependent Heat Transfer Coefficient Using an Accurate and Robust Parameter Estimation Approach: An Inverse Analysis. Energies. 2021; 14 (16):5073.
Chicago/Turabian StyleFarzad Mohebbi; Mathieu Sellier. 2021. "Estimation of Functional Form of Time-Dependent Heat Transfer Coefficient Using an Accurate and Robust Parameter Estimation Approach: An Inverse Analysis." Energies 14, no. 16: 5073.
The influence of surrounding fluid on a large array of oscillators is important to study for applications in fields such as medicine, biology, and atomic force microscopy. In the present study, we investigate a large array of cantilever beams oscillating in an unbounded fluid to better understand the fluid dynamic behavior. The two-dimensional boundary integral method is applied to analyze a large array of cantilever oscillators using an analytical solution approach for the unsteady Stokes and continuity equations. We analyze array sizes from 5 to 50 beams by comparing hydrodynamic transverse force and velocity profiles for two different velocity configurations. Including the interactions of neighbor and non-neighbor members leads to distinct array effects. With an increase in the number of oscillators in an array, the array effect influences the overall dynamics. Furthermore, to justify the influence of an array effect, the hydrodynamic loading is compared to the same and varying array surface area of different array sizes. Our analysis and new findings strengthen our hypothesis that the predictions of existing knowledge obtained from small-size arrays and coupled oscillators cannot readily inform dynamic predictions of large-size arrays. The underlying reason being the additional array effect(s) which are not present in a small-size array. The novelty of this paper is the ability to model such large arrays and investigate the array effect in an unbounded fluid.
Raghu Ande; Stefanie Gutschmidt; Mathieu Sellier. Fluid dynamics investigation of a large array. Physics of Fluids 2021, 33, 073608 .
AMA StyleRaghu Ande, Stefanie Gutschmidt, Mathieu Sellier. Fluid dynamics investigation of a large array. Physics of Fluids. 2021; 33 (7):073608.
Chicago/Turabian StyleRaghu Ande; Stefanie Gutschmidt; Mathieu Sellier. 2021. "Fluid dynamics investigation of a large array." Physics of Fluids 33, no. 7: 073608.
Geoff Willmott; Mathieu Sellier; Cassidy Wilgar; Fabien Montiel. Ka rere ngā mea katoa – everything flows. Journal of the Royal Society of New Zealand 2021, 51, 187 -193.
AMA StyleGeoff Willmott, Mathieu Sellier, Cassidy Wilgar, Fabien Montiel. Ka rere ngā mea katoa – everything flows. Journal of the Royal Society of New Zealand. 2021; 51 (2):187-193.
Chicago/Turabian StyleGeoff Willmott; Mathieu Sellier; Cassidy Wilgar; Fabien Montiel. 2021. "Ka rere ngā mea katoa – everything flows." Journal of the Royal Society of New Zealand 51, no. 2: 187-193.
Thermophotovoltaics systems involve a thermal-electrical energy conversion process. An energy efficient conversion is desirable for practical applications. In this work, thermal performances and emitter efficiency(ηE) assessments of two proposed unconventional micro-combustors, i.e. T- and Y-shaped are both experimentally and numerically conducted. Comparison is then made between the proposed combustion systems with the conventional I-shaped micro-combustor with premixed CH4/O2/Ar fueled. The effects of 1) the mass flow rate(m˙), 2) the equivalent ratio(φ) and 3) the extending depth of the flame holder (H) are numerically investigated using 3D models with structured meshes. The present results show that the thermal performances and the emitter efficiency of both T- and Y-shaped micro-combustors are significantly improved compared to the conventional I-shaped one under same conditions and key construction parameters. Furthermore, it is found that the bifurcation structure (T- and Y-shaped) can reduce the expanding area of the high temperature at the inlet and prevent the wall temperature from dropping too fast at the outlet. When φ is increased to 1.1, the flame position in the T-shaped combustor is found to be shifting away from the outlet of the flame holder, which results in more intensified combustion in the front area. The mean wall temperature shows a great improvement, when an optimal H is chosen. Overall, the Y-shaped combustor presents the best thermal performance with the largest ηE of 40.89% and a higher mean wall temperature of 765.1 K, when m˙=4.8×10−6kg/s and φ=0.8. These findings confirm a significant thermal improvement. This work opens up an energy efficient design of micro-combustors with unconventional structural shapes for thermophotovoltaic applications.
Siliang Ni; Dan Zhao; Mathieu Sellier; Junwei Li; Xinjian Chen; Xinyan Li; Feng Cao; Weixuan Li. Thermal performances and emitter efficiency improvement studies on premixed micro-combustors with different geometric shapes for thermophotovoltaics applications. Energy 2021, 226, 120298 .
AMA StyleSiliang Ni, Dan Zhao, Mathieu Sellier, Junwei Li, Xinjian Chen, Xinyan Li, Feng Cao, Weixuan Li. Thermal performances and emitter efficiency improvement studies on premixed micro-combustors with different geometric shapes for thermophotovoltaics applications. Energy. 2021; 226 ():120298.
Chicago/Turabian StyleSiliang Ni; Dan Zhao; Mathieu Sellier; Junwei Li; Xinjian Chen; Xinyan Li; Feng Cao; Weixuan Li. 2021. "Thermal performances and emitter efficiency improvement studies on premixed micro-combustors with different geometric shapes for thermophotovoltaics applications." Energy 226, no. : 120298.
This study presents an extension of a previous study (On an Exact Step Length in Gradient-Based Aerodynamic Shape Optimization) to viscous transonic flows. In this work, we showed that the same procedure to derive an explicit expression for an exact step length β exact in a gradient-based optimization method for inviscid transonic flows can be employed for viscous transonic flows. The extended numerical method was evaluated for the viscous flows over the transonic RAE 2822 airfoil at two common flow conditions in the transonic regime. To do so, the RAE 2822 airfoil was reconstructed by a Bezier curve of degree 16. The numerical solution of the transonic turbulent flow over the airfoil was performed using the solver ANSYS Fluent (using the Spalart–Allmaras turbulence model). Using the proposed step length, a gradient-based optimization method was employed to minimize the drag-to-lift ratio of the airfoil. The gradient of the objective function with respect to design variables was calculated by the finite-difference method. Efficiency and accuracy of the proposed method were investigated through two test cases.
Farzad Mohebbi; Ben Evans; Mathieu Sellier. On an Exact Step Length in Gradient-Based Aerodynamic Shape Optimization—Part II: Viscous Flows. Fluids 2021, 6, 106 .
AMA StyleFarzad Mohebbi, Ben Evans, Mathieu Sellier. On an Exact Step Length in Gradient-Based Aerodynamic Shape Optimization—Part II: Viscous Flows. Fluids. 2021; 6 (3):106.
Chicago/Turabian StyleFarzad Mohebbi; Ben Evans; Mathieu Sellier. 2021. "On an Exact Step Length in Gradient-Based Aerodynamic Shape Optimization—Part II: Viscous Flows." Fluids 6, no. 3: 106.
The conventional atomic force microscope (AFM) comprises a single cantilever with piezoelectric base excitation and optical read-out. The micro-electromechanical system is raster scanned over a sample surface to generate topographic measures as well as information on selected material properties. For some large sample surfaces and biological processes, a single cantilever scan may render insufficient scan speeds. We therefore consider developing small-size AFM array technology to improve scan rates by parallel processing scanned information. As a first step we investigate the collective and interactive fluid dynamics between members in an array away from any sample surface. Our analysis is based on Stokes equation for incompressible flow and the two-dimensional boundary integral method. We first formulate the generalized equations and then focus on three- and five-beam configurations. The fluid dynamic behaviour of these small-size arrays are investigated for different gaps between members, Reynolds numbers and actuation modes. Special emphasis is laid on the effect of non-neighbouring members, which often, if not always, has been neglected in the existing literature. One of our findings reveals a Reynolds number dependent concave/convex hydrodynamic loading profile across the array that is introduced by non-neighbouring members in the array.
Arun K. Manickavasagam; Stefanie Gutschmidt; Mathieu Sellier. Hydrodynamic loading profiles of viscously-interacting blocks subject to different stimulus locations. Journal of the Royal Society of New Zealand 2021, 51, 346 -360.
AMA StyleArun K. Manickavasagam, Stefanie Gutschmidt, Mathieu Sellier. Hydrodynamic loading profiles of viscously-interacting blocks subject to different stimulus locations. Journal of the Royal Society of New Zealand. 2021; 51 (2):346-360.
Chicago/Turabian StyleArun K. Manickavasagam; Stefanie Gutschmidt; Mathieu Sellier. 2021. "Hydrodynamic loading profiles of viscously-interacting blocks subject to different stimulus locations." Journal of the Royal Society of New Zealand 51, no. 2: 346-360.
Hydrogen is an excellent energy source for long-term storage and free of greenhouse gases. However, its high production cost remains an obstacle to its advancement. The two main parameters contributing to the high cost include the cost of electricity and the cost of initial financial investment. It is possible to reduce the latter by the optimization of system design and operation conditions, allowing the reduction of the cell voltage. Because the CAPEX (initial cost divided by total hydrogen production of the electrolyzer) decreases according to current density but the OPEX (operating cost depending on the cell voltage) increases depending on the current density, there exists an optimal current density. In this paper, a genetic algorithm has been developed to find the optimal evolution parameters and to determine an optimum electrolyzer design. The optimal current density has been increased by 10% and the hydrogen cost has been decreased by 1%.
Damien Le Bideau; Olivier Chocron; Philippe Mandin; Patrice Kiener; Mohamed Benbouzid; Mathieu Sellier; Myeongsub Kim; Fabrizio Ganci; Rosalinda Inguanta. Evolutionary Design Optimization of an Alkaline Water Electrolysis Cell for Hydrogen Production. Applied Sciences 2020, 10, 8425 .
AMA StyleDamien Le Bideau, Olivier Chocron, Philippe Mandin, Patrice Kiener, Mohamed Benbouzid, Mathieu Sellier, Myeongsub Kim, Fabrizio Ganci, Rosalinda Inguanta. Evolutionary Design Optimization of an Alkaline Water Electrolysis Cell for Hydrogen Production. Applied Sciences. 2020; 10 (23):8425.
Chicago/Turabian StyleDamien Le Bideau; Olivier Chocron; Philippe Mandin; Patrice Kiener; Mohamed Benbouzid; Mathieu Sellier; Myeongsub Kim; Fabrizio Ganci; Rosalinda Inguanta. 2020. "Evolutionary Design Optimization of an Alkaline Water Electrolysis Cell for Hydrogen Production." Applied Sciences 10, no. 23: 8425.
This research has found a novel computationally efficient method of modelling flow at low Reynolds number through fracture networks. The numerical analysis was performed by connecting Hele-Shaw cells to investigate the effect of intersections on the pressure field and hydraulic resistance for given inlet and outlet pressure values. In this analysis, the impact of intersecting length, intersecting angle and fracture aperture on the fluid flow was studied. For this purpose, two models with different topologies were established. The Hele-Shaw simulation results for hydraulic resistance, pressure and velocity agreed well with results obtained by solving the full Navier–Stokes equations (NSE). The results indicated an approximately linear relationship between intersection length and hydraulic resistance. Specifically, an increase in the intersection length increases the flow rate and as a result, the pressure along the intersection length decreases. The error associated with employing the Hele-Shaw approximation in comparison with NSE is less than 2%. All investigations were performed in the Reynolds Number range of 1–10.
Pouria Aghajannezhad; Mathieu Sellier; Sid Becker. Patching Hele-Shaw Cells to Investigate the Flow at Low Reynolds Number in Fracture Networks. Transport in Porous Media 2020, 136, 147 -163.
AMA StylePouria Aghajannezhad, Mathieu Sellier, Sid Becker. Patching Hele-Shaw Cells to Investigate the Flow at Low Reynolds Number in Fracture Networks. Transport in Porous Media. 2020; 136 (1):147-163.
Chicago/Turabian StylePouria Aghajannezhad; Mathieu Sellier; Sid Becker. 2020. "Patching Hele-Shaw Cells to Investigate the Flow at Low Reynolds Number in Fracture Networks." Transport in Porous Media 136, no. 1: 147-163.
Glacier ice flow is shaped and defined by several properties, including the bedrock elevation profile and the basal slip distribution. The effect of these two basal properties can be present in similar ways in the surface. For bedrock recovery, this makes distinguishing between them an interesting and complex problem. The results of this paper show that in some synthetic test cases it is indeed possible to distinguish and recover both bedrock elevation and basal slip given free surface elevation and free surface velocity. The unidirectional shallow ice approximation is used to compute steady-state surface data for a number of synthetic cases with different bedrock profiles and basal slip distributions. A simple inversion method based on Newton’s method is applied to the known surface data to return the bedrock profile and basal slip distribution. In each synthetic test case, the inversion was successful in recovering both the bedrock elevation profile and the basal slip distribution variables. These results imply that there are a unique bedrock profile and basal slip which give rise to a unique combination of free surface velocity and free surface elevation.
Elizabeth K. McGeorge; Mathieu Sellier; Miguel Moyers-Gonzalez; Phillip L. Wilson. Bedrock reconstruction from free surface data for unidirectional glacier flow with basal slip. Acta Mechanica 2020, 232, 305 -322.
AMA StyleElizabeth K. McGeorge, Mathieu Sellier, Miguel Moyers-Gonzalez, Phillip L. Wilson. Bedrock reconstruction from free surface data for unidirectional glacier flow with basal slip. Acta Mechanica. 2020; 232 (1):305-322.
Chicago/Turabian StyleElizabeth K. McGeorge; Mathieu Sellier; Miguel Moyers-Gonzalez; Phillip L. Wilson. 2020. "Bedrock reconstruction from free surface data for unidirectional glacier flow with basal slip." Acta Mechanica 232, no. 1: 305-322.
The conical diffuser is one of the oldest and most versatile hydraulic devices, however its performance is often less than optimal. This is because boundary layer separation and instabilities in the flow lead to energy losses through internal friction. Boundary layer suction offers a method for controlling and improving this flow, and some experimental studies have shown this to be effective – though they leave questions as to its net efficiency. This study takes a more comprehensive approach to suction control of the conical diffuser through the use of numerical studies coupled with optimisation. The flow through a conical diffuser with semi-divergence angle α = 5 ∘ was simulated by solving the full steady-state incompressible Navier-Stokes equations in the fully laminar Reynolds Number range R e ≤ 1400 . Uniform suction control was then applied in the divergent region, and optimisation methods used to determine the most effective suction strength for two objectives: (a) maximising the diffuser efficiency, and (b) minimising the separation length. It was found that suction control could increase the performance of the diffuser and was efficient even when considering the power to run the control. The results suggest that fluidic control of the diffuser should be reconsidered as it shows significant promise, particularly for applications where the constraints on the geometry of the diffuser are tight, for example in aircraft turbine engines.
James Ramsay; Mathieu Sellier; Wei Hua Ho. Effects of boundary layer suction control on flow through an axisymmetric diverging channel. Journal of the Royal Society of New Zealand 2020, 51, 389 -408.
AMA StyleJames Ramsay, Mathieu Sellier, Wei Hua Ho. Effects of boundary layer suction control on flow through an axisymmetric diverging channel. Journal of the Royal Society of New Zealand. 2020; 51 (2):389-408.
Chicago/Turabian StyleJames Ramsay; Mathieu Sellier; Wei Hua Ho. 2020. "Effects of boundary layer suction control on flow through an axisymmetric diverging channel." Journal of the Royal Society of New Zealand 51, no. 2: 389-408.
Hydrogen storage is a promising technology for storage of renewable energy resources. Despite its high energy density potential, the development of hydrogen storage has been impeded, mainly due to its significant cost. Although its cost is governed mainly by electrical energy expense, especially for hydrogen produced with alkaline water electrolysis, it is also driven by the value of the cell tension. The most common means of electrolyzer improvement is the use of an electrocatalyst, which reduces the energy required for electrochemical reaction to take place. Another efficient means of electrolyzer improvement is to use the Computational Fluid Dynamics (CFD)-assisted design that allows the comprehension of the phenomena occurring in the electrolyzer and also the improvement in the electrolyzer’s efficiency. The designed two-phase hydrodynamics model of this study has been compared with the experimental results of velocity profiles measured using Laser Doppler Velocimetry (LDV) method. The simulated results were in good agreement with the experimental data in the literature. Under the good fit with experimental values, it is efficient to introduce a new physical bubble transfer phenomenon description called “bubble diffusion”.
Damien Le Bideau; Philippe Mandin; Mohamed Benbouzid; Myeongsub Kim; Mathieu Sellier; Fabrizio Ganci; Rosalinda Inguanta. Eulerian Two-Fluid Model of Alkaline Water Electrolysis for Hydrogen Production. Energies 2020, 13, 3394 .
AMA StyleDamien Le Bideau, Philippe Mandin, Mohamed Benbouzid, Myeongsub Kim, Mathieu Sellier, Fabrizio Ganci, Rosalinda Inguanta. Eulerian Two-Fluid Model of Alkaline Water Electrolysis for Hydrogen Production. Energies. 2020; 13 (13):3394.
Chicago/Turabian StyleDamien Le Bideau; Philippe Mandin; Mohamed Benbouzid; Myeongsub Kim; Mathieu Sellier; Fabrizio Ganci; Rosalinda Inguanta. 2020. "Eulerian Two-Fluid Model of Alkaline Water Electrolysis for Hydrogen Production." Energies 13, no. 13: 3394.
In the present study, numerical investigations were performed with optimisation to determine efficient non-uniform suction profiles to control the flow around a circular cylinder in the range of Reynolds numbers 4 < Re < 188.5. Several objectives were explored, namely the minimisation of the separation angle, total drag, and pressure drag. This was in an effort to determine the relationships between the characteristics of the uncontrolled flow and the parameters of the optimised suction control. A variety of non-uniform suction configurations were implemented and compared to the benchmark performance of uniform suction. It was determined that the best non-uniform suction profiles consisted of a distribution with a single locus and compact support. The centre of suction on the cylinder surface for the optimised control, and the quantity of suction necessary to achieve each objective, varied substantially with Reynolds number and also with the separation angle of the uncontrolled flows. These followed predictable relationships. Surprisingly, the location of optimised suction to eliminate separation did not follow the separation point as it moved with Re, but rather it moved in opposition to it towards the trailing edge of the cylinder. Non-uniform suction profiles were much more efficient at eliminating boundary layer separation, requiring the removal of less than half the volume of fluid as uniform control to achieve the same objective. Regardless of the method of control, less net suction was needed to minimise total drag than to eliminate separation, except at low Re. The results suggest that controlling the dynamic aspects of the flow has the most impact for reducing drag. This reinforces the usefulness of other studies that focus on the elimination of vortex shedding. The results show that the balance of drag components must be an important consideration when designing flow control systems and that, when done appropriately, substantial improvement can be seen in the flow characteristics.
James Ramsay; Mathieu Sellier; Wei Hua Ho. Non-uniform suction control of flow around a circular cylinder. International Journal of Heat and Fluid Flow 2020, 82, 108559 .
AMA StyleJames Ramsay, Mathieu Sellier, Wei Hua Ho. Non-uniform suction control of flow around a circular cylinder. International Journal of Heat and Fluid Flow. 2020; 82 ():108559.
Chicago/Turabian StyleJames Ramsay; Mathieu Sellier; Wei Hua Ho. 2020. "Non-uniform suction control of flow around a circular cylinder." International Journal of Heat and Fluid Flow 82, no. : 108559.
High-speed imaging of water drop impacts on a polymer surface have been used alongside two-dimensional Lattice Boltzmann simulations to investigate the conditions under which a spreading lamella submerges a small surface ridge. Three basic outcomes have been observed when the lamella comes into contact with the ridge: pinning, wetting and splashing. The effects of Weber number and the dimensionless distance between the impact point and the ridge are investigated, and a phase portrait of the different wetting outcomes is presented. For each of the potential outcomes, a side-by-side comparison of experimental and numerical results can be made. An energy balance approach is used to study the transitions between the different outcomes.
Hossein Rashidian; Matheu Broom; Geoff R. Willmott; Mathieu Sellier. Effects of a microscale ridge on dynamic wetting during drop impact. Journal of the Royal Society of New Zealand 2020, 50, 523 -537.
AMA StyleHossein Rashidian, Matheu Broom, Geoff R. Willmott, Mathieu Sellier. Effects of a microscale ridge on dynamic wetting during drop impact. Journal of the Royal Society of New Zealand. 2020; 50 (4):523-537.
Chicago/Turabian StyleHossein Rashidian; Matheu Broom; Geoff R. Willmott; Mathieu Sellier. 2020. "Effects of a microscale ridge on dynamic wetting during drop impact." Journal of the Royal Society of New Zealand 50, no. 4: 523-537.
The evolution of a thin liquid film subject to a volatile solvent source and an air-blow effect which modifies locally the surface tension and leads to Marangoni-induced flow is shown to be governed by a degenerate fourth order nonlinear parabolic h-evolution equation of the type given by ∂ t h = − div x M 1 h ∂ x 3 h + M 2 h ∂ x h + M 3 h , where the mobility terms M 1 h and M 2 h result from the presence of the source and M 3 h results from the air-blow effect. Various authors assume M 2 h ≈ 0 and exclude the air-blow effect into M 3 h . In this paper, the authors show that such assumption is not necessarily correct, and the inclusion of such effect does disturb the dynamics of the thin film. These emphasize the importance of the full definition t → · grad γ = grad x γ + ∂ x h grad y γ of the surface tension gradient at the free surface in contrast to the truncated expression t → · grad γ ≈ grad x γ employed by those authors and the effect of the air-blow flowing over the surface.
Mohammad Irshad Khodabocus; Mathieu Sellier; Volker Nock. Dynamics of Thin Film Under a Volatile Solvent Source Driven by a Constant Pressure Gradient Flow. Fluids 2019, 4, 198 .
AMA StyleMohammad Irshad Khodabocus, Mathieu Sellier, Volker Nock. Dynamics of Thin Film Under a Volatile Solvent Source Driven by a Constant Pressure Gradient Flow. Fluids. 2019; 4 (4):198.
Chicago/Turabian StyleMohammad Irshad Khodabocus; Mathieu Sellier; Volker Nock. 2019. "Dynamics of Thin Film Under a Volatile Solvent Source Driven by a Constant Pressure Gradient Flow." Fluids 4, no. 4: 198.
This paper presents a novel and accurate method to implement the Kutta condition in solving subsonic (subcritical) inviscid isentropic compressible flow over isolated airfoils using the stream function equation. The proposed method relies on body-fitted grid generation and solving the stream function equation for compressible flows in computational domain using finite-difference method. An expression is derived for implementing the Kutta condition for the airfoils with both finite angles and cusped trailing edges. A comparison of the results obtained from the proposed numerical method and the results from experimental and other numerical methods reveals that they are in excellent agreement, which confirms the accuracy and correctness of the proposed method.
Farzad Mohebbi; Ben Evans; Mathieu Sellier. On the Kutta Condition in Compressible Flow over Isolated Airfoils. Fluids 2019, 4, 102 .
AMA StyleFarzad Mohebbi, Ben Evans, Mathieu Sellier. On the Kutta Condition in Compressible Flow over Isolated Airfoils. Fluids. 2019; 4 (2):102.
Chicago/Turabian StyleFarzad Mohebbi; Ben Evans; Mathieu Sellier. 2019. "On the Kutta Condition in Compressible Flow over Isolated Airfoils." Fluids 4, no. 2: 102.
Better understanding the properties of organic aerosols (OA) is attracting increasing attention because of the important role they play in climate change. The viscosity of OA has been shown to range from liquid to solid/semi-solid across the range of atmospheric relative humidity. A method known as the “bead-mobility technique” has been developed by Renbaum-Wolff et al. (Renbaum-Wolff, Grayson and Bertram 2013) to quantify the viscosity of an atmospheric particle over a range of atmospherically relevant humidities. The method is based on the assumption that the strength of the flow recirculation inside a droplet placed in a shear flow is related to the droplet viscosity. This paper presents a simple analytical model which predicts the internal flow in the droplet and provides a correlation relating the strength of the flow in the droplet to its viscosity. The validity of this analytical model is assessed by comparing the analytical results with a corresponding two-phase flow simulation with a moving mesh which captures the motion of the interface. The ability of the analytical model to reproduce experimental data reported in (Renbaum-Wolff, Grayson and Bertram 2013) is also quantified. The reasonable agreement between the analytical model and the experimental data confirms that the droplet velocity provides a useful proxy to estimate the droplet viscosity for small liquid samples for which standard viscometry techniques do not apply.
M. Sellier; J. Taylor; Allan K. Bertram; Philippe Mandin. Models for the bead mobility technique: A droplet-based viscometer. Aerosol Science and Technology 2019, 53, 749 -759.
AMA StyleM. Sellier, J. Taylor, Allan K. Bertram, Philippe Mandin. Models for the bead mobility technique: A droplet-based viscometer. Aerosol Science and Technology. 2019; 53 (7):749-759.
Chicago/Turabian StyleM. Sellier; J. Taylor; Allan K. Bertram; Philippe Mandin. 2019. "Models for the bead mobility technique: A droplet-based viscometer." Aerosol Science and Technology 53, no. 7: 749-759.
We study the behaviour of two-dimensional droplets of partially wetting liquids driven by thermocapillary forces. A sessile droplet over a non-uniformly heated surface undergoes a shear stress along the surface of the liquid that moves the droplet from warmer to colder regions. By means of a two-term disjoining pressure model with a single stable energy minimum, we introduce the effect of a non-zero contact angle and two different models are compared. Polar liquids are modelled using London–van der Waals and ionic-electrostatics molecular interactions and, non-polar fluids with long- and short-range molecular forces. The droplet dynamics model is based on the lubrication approximation and the resulting partial differential equation is solved in the Finite Element package COMSOL Multiphysics. As a result of a parametric study on the contact angle, we characterize three different regimes.
Jonatan Raúl Mac Intyre; Juan Manuel Gomba; Carlos Alberto Perazzo; Pablo Germán Correa; Mathieu Sellier. The Three Dynamical Regimes of a Droplet Driven by Thermocapillarity. IUTAM Symposium on Multiscale Modelling of Fatigue, Damage and Fracture in Smart Materials 2019, 85 -95.
AMA StyleJonatan Raúl Mac Intyre, Juan Manuel Gomba, Carlos Alberto Perazzo, Pablo Germán Correa, Mathieu Sellier. The Three Dynamical Regimes of a Droplet Driven by Thermocapillarity. IUTAM Symposium on Multiscale Modelling of Fatigue, Damage and Fracture in Smart Materials. 2019; ():85-95.
Chicago/Turabian StyleJonatan Raúl Mac Intyre; Juan Manuel Gomba; Carlos Alberto Perazzo; Pablo Germán Correa; Mathieu Sellier. 2019. "The Three Dynamical Regimes of a Droplet Driven by Thermocapillarity." IUTAM Symposium on Multiscale Modelling of Fatigue, Damage and Fracture in Smart Materials , no. : 85-95.
This study presents the modelling of an oblique drop impact on a textured substrate using the multiphase lattice Boltzmann method to understand the conditions under which the lamella lifts off the substrate and generates a satellite droplet. Depending on the impact angle and the Weber number, four various outcomes are observed: asymmetric spreading, bilateral splashing including a prompt splash and a corona splash, one-sided coronal splashing and asymmetric break-up. To obtain a better understanding of when splashing is likely to occur, a graph which shows splashing thresholds for a range of normal Weber numbers and impact angles between 5° and 45° is presented. Numerical results show that an increasing proportion of the droplet bounces off the surface in the form of satellite droplets for increasingly tangential impacts. Furthermore, the influence of substrate texture parameters such as the height of posts and wettability of the substrate are investigated. Results show that splashing vanishes as the wettability of the substrate increases. Also, the space between posts and the height of posts is shown to play an important role on the occurrence of splashing.
Hossein Rashidian; Mathieu Sellier. Oblique Impact of a Droplet on a Textured Substrate. IUTAM Symposium on Multiscale Modelling of Fatigue, Damage and Fracture in Smart Materials 2019, 119 -131.
AMA StyleHossein Rashidian, Mathieu Sellier. Oblique Impact of a Droplet on a Textured Substrate. IUTAM Symposium on Multiscale Modelling of Fatigue, Damage and Fracture in Smart Materials. 2019; ():119-131.
Chicago/Turabian StyleHossein Rashidian; Mathieu Sellier. 2019. "Oblique Impact of a Droplet on a Textured Substrate." IUTAM Symposium on Multiscale Modelling of Fatigue, Damage and Fracture in Smart Materials , no. : 119-131.
This paper investigates how and under which conditions the lamella of an impacting droplet is punctured by the presence of a small occlusion. Better understanding the conditions which lead to the rupture of the lamella is critical to produce defect free coating layers in the context of spray coating, for example. An analytical model based on surface energy analysis is proposed to obtain the critical thickness below which the liquid layer above the occlusion is unstable and lamella rupture occurs. Furthermore, we have developed a three dimensional multiphase lattice Boltzmann code to confirm the surface energy analysis and study the influence of key parameters like size of the occlusion, impact velocity and wettability of substrate on hole formation. Results show that a hole is more likely to appear as the diameter of the occlusion, the impact velocity, and the hydrophobicity of the surface increase.
Hossein Rashidian; Mathieu Sellier; Philippe Mandin. Dynamic wetting of an occlusion after droplet impact. International Journal of Multiphase Flow 2018, 111, 264 -271.
AMA StyleHossein Rashidian, Mathieu Sellier, Philippe Mandin. Dynamic wetting of an occlusion after droplet impact. International Journal of Multiphase Flow. 2018; 111 ():264-271.
Chicago/Turabian StyleHossein Rashidian; Mathieu Sellier; Philippe Mandin. 2018. "Dynamic wetting of an occlusion after droplet impact." International Journal of Multiphase Flow 111, no. : 264-271.
We derive an evolution equation for the free-surface dynamics of a thin film of a second-grade fluid over an unsteady stretching sheet using long-wave theory. For the numerical investigation of the viscoelastic effect on the thin-film dynamics, a finite-volume approach on a uniform grid with implicit flux discretization is applied. The present results are in excellent agreement with results available in the literature for a Newtonian fluid. We observe that the fluid thins faster with the rapid stretching rate of the sheet, but the second-grade parameter delays the thinning behaviour of the liquid film.doi:10.1017/S1446181118000251
Satyananda Panda; Kiran Kumar Patra; Mathieu Sellier. Free-surface dynamics of thin second-grade fluid over an unsteady stretching sheet. ANZIAM Journal 2018, 60, 249 -268.
AMA StyleSatyananda Panda, Kiran Kumar Patra, Mathieu Sellier. Free-surface dynamics of thin second-grade fluid over an unsteady stretching sheet. ANZIAM Journal. 2018; 60 ():249-268.
Chicago/Turabian StyleSatyananda Panda; Kiran Kumar Patra; Mathieu Sellier. 2018. "Free-surface dynamics of thin second-grade fluid over an unsteady stretching sheet." ANZIAM Journal 60, no. : 249-268.