Static arrangement of a capillary porous system (CPS): Modelling

Pelekasis, N.; Benos, Lefteris

doi:10.1016/j.fusengdes.2016.06.059

Cited by 6 publications

(5 citation statements)

References 18 publications

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“…Our numerical results were also tested against the Washburn equation as will be discussed in subsection 6.3. As far as the electrostatic model is concerned, comparison of the present numerical approach for the static arrangement of a polymeric droplet that rests on a solid surface with a fixed contact angle θ c = 60 o , Bond el = 5.06 and Bond = 0.33, against the boundary element solution obtained by Reznik et al, [92], indicates that our results agree with the maximum and minimum values of z and r, respectively, for the case of negligible electric stress [108], Fig 5 .19. However, partial agreement is observed, when the case with an external electric field is studied.…”

Section: Benchmark Case Studiessupporting

confidence: 69%

First principles study of the static arrangement of a plasma facing component in the form of a capillary porous system (CPS)

Benos¹,

Μπένος²

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Η παρούσα Διδακτορική Διατριβή επικεντρώνεται στην μοντελοποίηση εναλλακτικών στοιχείων αντιμετώπισης του πλάσματος υπό μορφή υγρών μετάλλων έτσι ώστε να προστατευτούν τα τοιχώματα του αντιδραστήρα από προβλήματα που σχετίζονται με την αλληλεπίδρασή τους με το πλάσμα, όπως τα πολύ υψηλά θερμικά φορτία και τα μεγάλα φορτία ηλεκτρικού ρεύματος που δημιουργούνται στο κέντρο του αντιδραστήρα και κατευθύνονται προς τον divertor. Τα στοιχεία αντιμετώπισης του πλάσματος υπό μορφή υγρών μετάλλων αποτελούν μία από τις πιο ζωτικής σημασίας τεχνολογικές προκλήσεις των μελλοντικών αντιδραστήρων σύντηξης. Η παρούσα Διδακτορική Διατριβή επικεντρώνεται στη συστοιχία από τζετ ή σταγόνες και κυρίως στην τριχοειδή πορώδη διάταξη (CPS).Όσο αναφορά την μελέτη σχετικά με την συστοιχία από τζετ ή σταγόνες, το απλοποιημένο αριθμητικό μοντέλο παρέχει μια πρώτη εξήγηση για την εκτροπή των παραπάνω από την αρχική τους πορεία σε ένα περιβάλλον TOKAMAK. Επιπλέον, η παρούσα Διδακτορική Διατριβή προσπαθεί μέσα από βασικές αρχές να περιγράψει τις κύριες φάσεις λειτουργίας του CPS. Συγκεκριμένα, μοντελοποιεί-εξηγεί τι συμβαίνει πριν η μηχανή "ανοίξει". Εν συνεχεία, μελετάει τη διεργασία ανατροφοδότησης του υγρού μετάλλου, που ακολουθάει την εξάντλησή του εξαιτίας ενός τεράστιου θερμικού φορτίου, έτσι ώστε να αναγνωριστούν οι κυρίαρχες δυνάμεις που λαμβάνουν χώρα και ενεργούν έτσι ώστε να σπρώχνουν το υγρό μέταλλο προς τα έξω ή ανθίστανται στην κίνησή του. Τέλος, η παρούσα Διδακτορική Διατριβή μελετάει εκτενώς την στατική διαμόρφωση του υγρού μετάλλου υπό μορφή υγρού υμένα που σχηματίζεται στην άνω επιφάνεια του CPS, ως συνάρτηση της επίδρασης της διαφοράς πίεσης, της τοπογραφίας του πορώδους υποστρώματος, εξωτερικών πεδιακών δυνάμεων και ιδιοτήτων διαβροχής του υγρού μετάλλου με το στερεό υπόστρωμα. Εν συντομία, διαπιστώθηκε ότι για ρεαλιστικές διαφορές πίεσης, δηλαδή κοντά σε καταστάσεις κενού, υγροί υμένες τάξεως μικρομέτρων και υπο-μικρομέτρων σχηματίζονται. Σε αυτή την περιοχή το μέγεθος του πόρου και η τοπογραφία του αρχίζουν να παίζουν πολύ σημαντικό ρόλο στην στατική διαμόρφωση. Επίσης, βρέθηκε μία κρίσιμη τιμή της διαφοράς πίεσης, πέραν της οποίας η στατική διαμόρφωση δεν μπορεί να επιτευχθεί. Στην παρουσία ενός μαγνητικού πεδίου και ενός προσπίπτοντος ηλεκτρικού ρεύματος η προαναφερθείσα στατική διαμόρφωση επηρεάζεται εξαιτίας των τάσεων Maxwell που αναπτύσσονται, ενώ η διεπιφάνεια με το πλάσμα σπρώχνεται έξω από τον πόρο όσο η μαγνητική πίεση αυξάνεται.

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Section: Benchmark Case Studiessupporting

confidence: 69%

First principles study of the static arrangement of a plasma facing component in the form of a capillary porous system (CPS)

Benos¹,

Μπένος²

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“…The latter is envisioned as a means to protect the divertor wall of a fusion reactor from the high fluxes of heat and particles released by plasma activity in the bulk of the reactor. Clearly, the interaction between the CPS and the surrounding plasma is more complex in reality, but this simplified approach, which has also been previously used in [19,20] and possibly leads to an overestimation of the system's permeability [19], is necessary in order to obtain an in-depth understanding of the involved phenomena and the manner in which they affect the dynamic behavior of the liquid-metal interface. It is therefore important to perform a more extensive parametric analysis that examines the effect of other parameters as well, like the pore size, the intensity of the magnetic field, and the structure of the porous medium.…”

Section: Discussionmentioning

confidence: 99%

“…with u l and u s,n denoting the normal velocity of the liquid at the interface and of the interface, respectively, n the unit normal vector at the interface pointing outwards with respect to the liquid metal, and r s = r int (ξ)e r + z int (ξ)e z is the Lagrangian representation of the interface. Furthermore, we adopted a fixed contact point approach [19,20] for the shape of the interface as it approaches the pore-substrate interface at the top, and the boundary conditions corresponding to the liquid metal velocity and the location of the interface at the pore wall are:…”

Section: Problem Formulationmentioning

confidence: 99%

“…An emphasis was placed on understanding the interplay between the different forces that act towards pushing the liquid metal out of the pore or resist its motion and in determining the conditions and the limits for stable power exhaust. We followed the approach of Benos et al [19,20], who studied the static arrangement of the liquid metal, both when it is limited inside a single pore using a fixed contact point approach and while it rests on the CPS top surface. More specifically, in the latter study, the effects of the reservoir overpressure, electric stresses, and Lorentz force (jxB) effects were investigated on the static film arrangement.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Study of a Liquid Metal Oscillating inside a Pore in the Presence of Lorentz and Capillary Forces

Vlachomitrou

Pelekasis

2020

Fluids

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In order to ensure stable power exhaust and to protect the walls of fusion reactors, liquid metals that are fed to the wall surface through a capillary porous system (CPS) are considered as alternative plasma-facing components (PFCs). However, operational issues like drop ejection and plasma contamination may arise. In this study, the unsteady flow of a liquid metal inside a single pore of the CPS in the presence of Lorentz forces is investigated. A numerical solution is performed via the finite element methodology coupled with elliptic mesh generation. A critical magnetic number is found (Bondm = 4.5) below which the flow after a few oscillations reaches a steady state with mild rotational patterns. Above this threshold, the interface exhibits saturated oscillations. As the Lorentz force is further increased, Bondm > 5.8, a Rayleigh–Taylor instability develops as the interface is accelerated under the influence of the increased magnetic pressure and a finite time singularity is captured. It is conjectured that eventually, drop ejection will take place that will disrupt cohesion of the interface and contaminate the surrounding medium. Finally, the dynamic response of different operating fluids is investigated, e.g., gallium, and the stabilizing effect of increased electrical conductivity and surface tension is demonstrated.

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“…The stability analysis of liquid metal PFCs in plasmas has been conducted by several authors [20,[24][25][26][27][28][29]. In the current study, the focus is on the static planar liquid surface exposed to a magnetized plasma under the influences of a sheath electric field (E Φ ) and an external magnetic field (B 0 ).…”

Section: Methodsmentioning

confidence: 99%

Surface instability of static liquid metal in magnetized fusion plasma

Somboonkittichai

Zuo

2023

Nucl. Fusion

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Understanding surface instability in magnetized fusion plasma supports the appropriate implementation and handling of liquid metal as plasma facing components (PFCs) in future fusion reactors. A Lagrange equation describing a viscous liquid surface deformation in a magnetized plasma is derived using Rayleigh's method. Its solution justifies the general instability criterion and helps in characterizing the key interactions driving such instability under fusion conditions. Surface tension and gravity, especially with the poloidal angles of the lower part of a plasma chamber, mainly stabilize the liquid surface at small and large disturbance wavelengths, respectively. The sheath electric field and the external tangential magnetic field cause the liquid surface to disintegrate at an intermediate wavelength. Practically, a magnetic confinement fusion (MCF) device requires a strong magnetic field for confinement. The study suggests that such a strong field dominates the rest and governs instability. In addition, this implies that the configuration of a static planar free liquid surface is difficult to adopt as a candidate for handling the liquid metal as PFCs in next step MCF devices.

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Static arrangement of a capillary porous system (CPS): Modelling

Cited by 6 publications

References 18 publications

First principles study of the static arrangement of a plasma facing component in the form of a capillary porous system (CPS)

First principles study of the static arrangement of a plasma facing component in the form of a capillary porous system (CPS)

Numerical Study of a Liquid Metal Oscillating inside a Pore in the Presence of Lorentz and Capillary Forces

Surface instability of static liquid metal in magnetized fusion plasma

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