OpenFOAM Finite Volume Solver for Fluid-Solid Interaction

This paper describes a self-contained parallel fluid-structure interaction solver based on a finite volume discretisation, where a strongly coupled partitioned solution procedure is employed. The incompressible fluid flow is described by the Navier-Stokes equations in the arbitrary Lagrangian-Eulerian form, and the solid deformation is described by the Saint Venant-Kirchhoff hyperelastic model in the total Lagrangian form. Both the fluid and the solid are discretised in space using the second-order accurate cell-centred finite volume method, and temporal discretisation is performed using the second-order accurate implicit scheme. The method, implemented in open-source software OpenFOAM, is parallelised using the domain decomposition approach and the exchange of information at the fluid-solid interface is handled using global face zones. The performance of the solver is evaluated in standard two- and threedimensional cases and excellent agreement with the available numerical results is obtained

Analytical and numerical stress analysis of the rotary kiln ring

Ovaj rad predstavlja analizu raspodjele naprezanja na vanjskoj površini nosivog prstena rotacijske peći u radnom ciklusu uporabom teorijske analize i simulacije metodom konačnih elemenata. U teorijskoj analizi, ukupno naprezanje je dobiveno kombinacijom savojnog naprezanja, toplinskih i kontaktnih naprezanja. Za dobivanje savojnog naprezanja, peć se promatra kao prosta, statički neodređena greda koja je opterećena statičkim i simetričnim opterećenjima, pri čemu se koristi Castiglianov teorem. Toplinska naprezanja dobivena su pretpostavljajući i linearnu i nelinearnu raspodjelu temperature kroz debljinu prstena. Konstantna naprezanja između prstena i nosivih valjaka dobivena su uporabom Hertzove teorije za kontaktna naprezanja. Naprezanja uslijed savijanja, toplinska i kontaktna naprezanja dobivena su i numerički u odvojenim simulacijama, u kojima su korišteni uvjeti usvojeni u teorijskom dijelu. Svi se rezultati odlično slažu. Pored toga, simuliran je i realniji model prstena koji je izložen svim naprezanjima istovremeno. Ovi rezultati pokazali su manja odstupanja od teorije, naročito zbog klizajućeg kontakta između prstena i nosivih valjaka, ali se općenito dobro slažu.This paper presents an analysis of the stress distribution on the outer surface of the riding ring of rotary cement kiln during working cycle using both the theory and finite element simulation. In the theoretical analysis, the total stress is obtained as a combination of bending, thermal and contact stresses. To obtain bending stress the kiln is considered as a simply supported, indeterminate beam subjected to static and symmetrical loads and Castigliano’s theorem is employed. Thermal stresses are obtained assuming both linear and non-linear temperature distribution over the ring thickness. Contact stress between ring and supporting rollers is obtained using Hertz contact theory. Bending, thermal and contact stresses are also obtained numerically in separate simulations, mimicking conditions assumed in the theoretical part. All results are in excellent agreement. In addition, a more realistic ring model subjected to all loads simultaneously is also simulated. These results showed slight disagreement with theory in the contact region, mainly due to sliding contact between the roller and the ring, but overall agreement was good

Investigation of the mixed-mode fracture in delamination tests: numerical simulations using cohesive zone and partitioning methods

U radu se istražuju pokusi delaminacije (loma) pomoću numeričkih simulacija u kojima su korištene različite osobine kohezivnih zona. Koristili su se asimetrični i simetrični dvokraki gredni uzorci opterećeni momentom savijanja. Udjeli tipa I i tipa II loma u ukupnoj energiji loma su proračunati pomoću globalnog i lokalnog pristupa. Rezultati mješovitog tipa loma su prezentirani i analizirani. Numeričke vrijednosti podjele energije za različite konfiguracije su uspoređene s dvije analitičke teorije podjele energije, koje su postavili Williams te Hutchison i Suo. Nasuprot teorijama, uočena je ovisnost podjele energije o osobinama kohezivne zone.Delamination (fracture) tests have been numerically investigated using various cohesive zone properties. The test utilises asymmetric and symmetric double cantilever beam specimens loaded with bending moment. Energy release rate contributions from mode I and mode II fracture are calculated using a global and local approach. Mode-mixities results are presented and analysed. The numerical partitioning results for different configurations are compared to two analytical partitioning theories, namely, after Williams and after Hutchinson and Suo. Opposite to these theories, partitioning is observed to be dependent on cohesive zone properties

Analytical and numerical stress analysis of the rotary kiln ring

Ovaj rad predstavlja analizu raspodjele naprezanja na vanjskoj površini nosivog prstena rotacijske peći u radnom ciklusu uporabom teorijske analize i simulacije metodom konačnih elemenata. U teorijskoj analizi, ukupno naprezanje je dobiveno kombinacijom savojnog naprezanja, toplinskih i kontaktnih naprezanja. Za dobivanje savojnog naprezanja, peć se promatra kao prosta, statički neodređena greda koja je opterećena statičkim i simetričnim opterećenjima, pri čemu se koristi Castiglianov teorem. Toplinska naprezanja dobivena su pretpostavljajući i linearnu i nelinearnu raspodjelu temperature kroz debljinu prstena. Konstantna naprezanja između prstena i nosivih valjaka dobivena su uporabom Hertzove teorije za kontaktna naprezanja. Naprezanja uslijed savijanja, toplinska i kontaktna naprezanja dobivena su i numerički u odvojenim simulacijama, u kojima su korišteni uvjeti usvojeni u teorijskom dijelu. Svi se rezultati odlično slažu. Pored toga, simuliran je i realniji model prstena koji je izložen svim naprezanjima istovremeno. Ovi rezultati pokazali su manja odstupanja od teorije, naročito zbog klizajućeg kontakta između prstena i nosivih valjaka, ali se općenito dobro slažu.This paper presents an analysis of the stress distribution on the outer surface of the riding ring of rotary cement kiln during working cycle using both the theory and finite element simulation. In the theoretical analysis, the total stress is obtained as a combination of bending, thermal and contact stresses. To obtain bending stress the kiln is considered as a simply supported, indeterminate beam subjected to static and symmetrical loads and Castigliano’s theorem is employed. Thermal stresses are obtained assuming both linear and non-linear temperature distribution over the ring thickness. Contact stress between ring and supporting rollers is obtained using Hertz contact theory. Bending, thermal and contact stresses are also obtained numerically in separate simulations, mimicking conditions assumed in the theoretical part. All results are in excellent agreement. In addition, a more realistic ring model subjected to all loads simultaneously is also simulated. These results showed slight disagreement with theory in the contact region, mainly due to sliding contact between the roller and the ring, but overall agreement was good

Implementation of the electrohydrodynamics’ perfect dielectric model in OpenFOAM®

The electrohydrodynamics’ (EHD) perfect dielectric model was added into computational fluid dynamics (CFD) software OpenFOAM® in order to improve its usability for the EHD field and specifically for the mentioned model. Based on the investigated literature, it can be said that this is the most complete implementatiton of the said model. Two sets of numerical simulations with two different fluids are presented and analyzed. One set is one-dimensional. The other set is with a drop of one fluid surrounded by other fluid. Oscillations can be observed with certain expressions or calculation strategies for the electrostrictive force, and used for disregarding them. Results that are closer to analytical predictions can be obtained by using appropriate expression for the dielectric force. The electrostrictive force was implemented not only for nonpolar, but also for polar fluids, and it is shown that it might significantly influence the drop deformation. Calculated and analytically predicted drop deformations were close or comparable even up to around 0.25, what is significantly higher and different from a previous study made by other authors. Different expressions for the electric permittivity and usage of limiters for volume fractions were investigated. Conclusions from this paper can be transferred to more complicated models

Conductive Compartmented Capsules Encapsulating a Bitumen Rejuvenator

This paper explores the potential use of conductive alginate capsules encapsulating a bitumen rejuvenator as a new extrinsic self-healing asphalt method. The capsules combine two existing self-healing asphalt technologies: (1) rejuvenator encapsulation and (2) induction heating to create a self-healing system that will provide rapid and effective asphalt pavement repair. The work presents a proof of concept for the encapsulation process, which involves embedding the capsules into the bitumen mortar mixture and the survival rate of the capsules in the asphalt mixture. A drip capsule production process was adopted and scaled up to the production of 20l wet capsules at rate of 0.22 l/min. To prove the effectiveness and its ability to survive asphalt production process, the capsules were prepared and subjected to thermogravimetric analysis (TGA) and uniaxial compression Test (UCT). The test results demonstrated that the capsules had suitable thermal characteristics and mechanical strength to survive the asphalt mixing and compaction process. Scanning electron microscopy (SEM) was employed to investigate physiological properties, such as rejuvenator (oil) and iron particle distribution, within the capsules. The electrical resistance tests proved that the capsules were capable of conducting electrical current. The capsules were also tested for their conductive properties in order to determine whether they are capable of conducting and distributing the heat once subjected to induction heating. The results showed that capsules containing higher amounts of iron (alginate/iron powder in a ratio of 20:80 by weight) can efficiently conduct and distribute heat. To prove its success as an asphalt healing system, conductive alginate capsules encapsulating a bitumen rejuvenator were embedded in a bitumen mortar mix. The samples where then subjected to local damaging and healing events, and the degree of healing was quantified. The research findings indicate that conductive alginate capsules encapsulating a bitumen rejuvenator present a promising new approach for the development of an extrinsic self-healing asphalt pavement systems

Ispitivanje elektrohidrodinamičkih proračuna

A perfect dielectric model was incorporated into the OpenFOAM® software and used for investigation and, possibly, improvements of electrohydrodynamic calculations. Two different sets of numerical simulations were analyzed, in which two different fluids were present. The first set was one-dimensional, while in the second, a drop of one fluid was surrounded by the other fluid. It is shown that oscillations and possibly artificial generation of a curl of the electric field strength can be observed at applying certain expressions or calculation strategies, which can be thus abandoned. Usage of dynamic meshes, at least those present in the used software, and of limiters for the gradient of the electric field strength can lead to large numerical errors. It is also shown that usage of certain cell face values could improve the results. An electric Courant number was derived by dimensional analysis, and it could be suggested for future calculations. Conclusions made in this paper are expected to be transferable to other more complicated models.Model idealnog dielektrika je uključen u programski paket OpenFOAM® (OpenFOAM Foundation, UK) i korišćen za ispitivanje i moguće poboljšavanje elektrohidrodinamičkih proračuna. Analizirana su dva različita seta numeričkih simulacija, u kojima su bila modelovana dva različita fluida. Prvi set je bio jednodimenzionalan dok je u drugom setu kap jednog fluida bila okružena drugim fluidom. U radu je pokazano da se određeni izrazi ili strategije izračunavanja mogu odbaciti usled pojave oscilacija i mogućeg veštačkog stvaranja rotora jačine električnog polja. Korišćenje pokretnih mreža, barem onih prisutnih u programskom paketu OpenFOAM®, i limitera za gradijent jačine električnog polja mogu dovesti do velikih numeričkih grešaka. Takođe je pokazano da bi korišćenje određenih vrednosti sa površi ćelija moglo poboljšati rezultate. Izraz za električni Kuronov broj je izveden dimenzionom analizom i mogao bi se preporučiti za buduće proračune. Očekuje se da su zaključci iz ovog rada prenosivi na druge, komplikovanije modele

Conductive compartmented capsules encapsulating a bitumen rejuvenator

This paper explores the potential use of conductive alginate capsules encapsulating a bitumen rejuvenator as a new extrinsic self-healing asphalt method. The capsules combine two existing self-healing asphalt technologies: (1) rejuvenator encapsulation and (2) induction heating to create a self-healing system that will provide rapid and effective asphalt pavement repair. The work presents a proof of concept for the encapsulation process, which involves embedding the capsules into the bitumen mortar mixture and the survival rate of the capsules in the asphalt mixture. A drip capsule production process was adopted and scaled up to the production of 20l wet capsules at rate of 0.22 l/min. To prove the effectiveness and its ability to survive asphalt production process, the capsules were prepared and subjected to thermogravimetric analysis (TGA) and uniaxial compression Test (UCT). The test results demonstrated that the capsules had suitable thermal characteristics and mechanical strength to survive the asphalt mixing and compaction process. Scanning electron microscopy (SEM) was employed to investigate physiological properties, such as rejuvenator (oil) and iron particle distribution, within the capsules. The electrical resistance tests proved that the capsules were capable of conducting electrical current. The capsules were also tested for their conductive properties in order to determine whether they are capable of conducting and distributing the heat once subjected to induction heating. The results showed that capsules containing higher amounts of iron (alginate/iron powder in a ratio of 20:80 by weight) can efficiently conduct and distribute heat. To prove its success as an asphalt healing system, conductive alginate capsules encapsulating a bitumen rejuvenator were embedded in a bitumen mortar mix. The samples where then subjected to local damaging and healing events, and the degree of healing was quantified. The research findings indicate that conductive alginate capsules encapsulating a bitumen rejuvenator present a promising new approach for the development of an extrinsic self-healing asphalt pavement systems.Materials and Environmen