subject:(computational mechanics)

ETH Zürich

451. Vicum, Lars. Investigation of the influence of turbulent mixing on precipitation processes carried out in stirred tank reactors.

Degree: 2005, ETH Zürich

URL: http://hdl.handle.net/20.500.11850/73421

Subjects/Keywords: AUSFÄLLEN + ERSTARREN + KRISTALLISIEREN (VERFAHRENSTECHNIK); CRYSTALL GROWING + CRYSTAL GROWTH; HOMOGENISIEREN UND MISCHEN (CHEMISCHE LABORTECHNIK); TURBULENT FLOW (FLUID DYNAMICS); STIRRING + HOMOGENIZATION + STIRRING DEVICES (PROCESS ENGINEERING); HOMOGENIZATION AND MIXING (PRACTICAL LABORATORY CHEMISTRY); MODELLRECHNUNG IN DER TECHNISCHEN CHEMIE UND VERFAHRENSTECHNIK; COMPUTATIONAL FLUID DYNAMICS (FLUIDMECHANIK); TURBULENTE STRÖMUNG (FLUIDDYNAMIK); MATHEMATICAL MODELING IN TECHNICAL CHEMISTRY AND PROCESS ENGINEERING; RÜHREN + HOMOGENISIEREN + RÜHRVORRICHTUNGEN (VERFAHRENSTECHNIK); CHEMICAL REACTIONS; COMPUTATIONAL FLUID DYNAMICS (FLUID MECHANICS); KRISTALLZÜCHTUNG + KRISTALLWACHSTUM; PRECIPATION + SOLIDIFICATION + CRYSTALLIZATION (PROCESS ENGINEERING); CHEMISCHE REAKTIONEN; DISCONTINUOUS PROCESSES (CHEMICAL ENGINEERING); DISKONTINUIERLICHE VERFAHREN (CHEMISCHE VERFAHRENSTECHNIK); info:eu-repo/classification/ddc/660; Chemical engineering

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Vicum, L. (2005). Investigation of the influence of turbulent mixing on precipitation processes carried out in stirred tank reactors. (Doctoral Dissertation). ETH Zürich. Retrieved from http://hdl.handle.net/20.500.11850/73421

Chicago Manual of Style (16^th Edition):

Vicum, Lars. “Investigation of the influence of turbulent mixing on precipitation processes carried out in stirred tank reactors.” 2005. Doctoral Dissertation, ETH Zürich. Accessed December 13, 2019. http://hdl.handle.net/20.500.11850/73421.

MLA Handbook (7^th Edition):

Vicum, Lars. “Investigation of the influence of turbulent mixing on precipitation processes carried out in stirred tank reactors.” 2005. Web. 13 Dec 2019.

Vancouver:

Vicum L. Investigation of the influence of turbulent mixing on precipitation processes carried out in stirred tank reactors. [Internet] [Doctoral dissertation]. ETH Zürich; 2005. [cited 2019 Dec 13]. Available from: http://hdl.handle.net/20.500.11850/73421.

Council of Science Editors:

Vicum L. Investigation of the influence of turbulent mixing on precipitation processes carried out in stirred tank reactors. [Doctoral Dissertation]. ETH Zürich; 2005. Available from: http://hdl.handle.net/20.500.11850/73421

ETH Zürich

452. Schleer, Matthias Wolfgang. Flow structure and stability of a turbocharger centrifugal compressor.

Degree: 2006, ETH Zürich

URL: http://hdl.handle.net/20.500.11850/149389

Subjects/Keywords: VERBRENNUNGSKRAFTMASCHINEN (WÄRMEKRAFTMASCHINEN); AUFLADUNG, LADER (VERBRENNUNGSMOTOREN); VERDICHTER, KOMPRESSOREN (MASCHINENBAU); KREISELVERDICHTER, TURBOKOMPRESSOREN (MASCHINENBAU); ROTOREN, LAUFRÄDER (TURBOMASCHINEN); FLUID-STRUKTUR-WECHSELWIRKUNGEN (FLUIDDYNAMIK); DYNAMISCHE INSTABILITÄT (FLUIDDYNAMIK); LASER-DOPPLER-ANEMOMETRIE, LDA (AERO-, FLUIDDYNAMIK); COMPUTATIONAL FLUID DYNAMICS (FLUIDMECHANIK); INTERNAL COMBUSTION ENGINES (HEAT ENGINES); COMPRESSION OF THE GASEOUS CHARGE (INTERNAL COMBUSTION ENGINES); COMPRESSORS (MECHANICAL ENGINEERING); CENTRIFUGAL COMPRESSORS, TURBOCOMPRESSORS (MECHANICAL ENGINEERING); ROTORS, IMPELLERS (TURBOMACHINES); FLUID-STRUCTURE INTERACTIONS (FLUID DYNAMICS); DYNAMIC INSTABILITY (FLUID DYNAMICS); LASER-DOPPLER ANEMOMETRY, LDA (AERO-, FLUID DYNAMICS); COMPUTATIONAL FLUID DYNAMICS (FLUID MECHANICS); info:eu-repo/classification/ddc/620; info:eu-repo/classification/ddc/530; Engineering & allied operations; Physics

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Schleer, M. W. (2006). Flow structure and stability of a turbocharger centrifugal compressor. (Doctoral Dissertation). ETH Zürich. Retrieved from http://hdl.handle.net/20.500.11850/149389

Chicago Manual of Style (16^th Edition):

Schleer, Matthias Wolfgang. “Flow structure and stability of a turbocharger centrifugal compressor.” 2006. Doctoral Dissertation, ETH Zürich. Accessed December 13, 2019. http://hdl.handle.net/20.500.11850/149389.

MLA Handbook (7^th Edition):

Schleer, Matthias Wolfgang. “Flow structure and stability of a turbocharger centrifugal compressor.” 2006. Web. 13 Dec 2019.

Vancouver:

Schleer MW. Flow structure and stability of a turbocharger centrifugal compressor. [Internet] [Doctoral dissertation]. ETH Zürich; 2006. [cited 2019 Dec 13]. Available from: http://hdl.handle.net/20.500.11850/149389.

Council of Science Editors:

Schleer MW. Flow structure and stability of a turbocharger centrifugal compressor. [Doctoral Dissertation]. ETH Zürich; 2006. Available from: http://hdl.handle.net/20.500.11850/149389

ETH Zürich

453. Demiraydin, Lale. Numerical investigation of turbulent nonpremixed methane-air flames.

Degree: 2002, ETH Zürich

URL: http://hdl.handle.net/20.500.11850/147322

Subjects/Keywords: VERBRENNUNG (VERBRENNUNGSMOTOREN); METHAN (BRENNSTOFFTECHNOLOGIE); FLAMMEN/TEMPERATURVERTEILUNG (BRENNSTOFFTECHNOLOGIE); CHEMISCHE REAKTIONEN; TURBULENTE STRÖMUNG (FLUIDDYNAMIK); COMPUTATIONAL FLUID DYNAMICS (FLUIDMECHANIK); NUMERISCHE SIMULATION UND MATHEMATISCHE MODELLRECHNUNG; STICKSTOFFOXIDE (UMWELTSCHADSTOFFE); ABGASE, BEHANDLUNG DER ABGASE (VERBRENNUNGSMOTOREN); COMBUSTION (INTERNAL COMBUSTION ENGINES); METHANE (FUEL TECHNOLOGY); FLAMES/TEMPERATURE DISTRIBUTION (FUEL TECHNOLOGY); CHEMICAL REACTIONS; TURBULENT FLOW (FLUID DYNAMICS); COMPUTATIONAL FLUID DYNAMICS (FLUID MECHANICS); NUMERICAL SIMULATION AND MATHEMATICAL MODELING; NITROGEN OXIDES (ENVIRONMENTAL POLLUTANTS); EXHAUST GASES AND TREATMENT (INTERNAL COMBUSTION ENGINES); info:eu-repo/classification/ddc/620; info:eu-repo/classification/ddc/530; info:eu-repo/classification/ddc/530; Engineering & allied operations; Physics; Physics

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Demiraydin, L. (2002). Numerical investigation of turbulent nonpremixed methane-air flames. (Doctoral Dissertation). ETH Zürich. Retrieved from http://hdl.handle.net/20.500.11850/147322

Chicago Manual of Style (16^th Edition):

Demiraydin, Lale. “Numerical investigation of turbulent nonpremixed methane-air flames.” 2002. Doctoral Dissertation, ETH Zürich. Accessed December 13, 2019. http://hdl.handle.net/20.500.11850/147322.

MLA Handbook (7^th Edition):

Demiraydin, Lale. “Numerical investigation of turbulent nonpremixed methane-air flames.” 2002. Web. 13 Dec 2019.

Vancouver:

Demiraydin L. Numerical investigation of turbulent nonpremixed methane-air flames. [Internet] [Doctoral dissertation]. ETH Zürich; 2002. [cited 2019 Dec 13]. Available from: http://hdl.handle.net/20.500.11850/147322.

Council of Science Editors:

Demiraydin L. Numerical investigation of turbulent nonpremixed methane-air flames. [Doctoral Dissertation]. ETH Zürich; 2002. Available from: http://hdl.handle.net/20.500.11850/147322

ETH Zürich

454. Lämmle, Christian. Numerical and experimental study of flame propagation and knock in a compressed natural gas engine.

Degree: 2005, ETH Zürich

URL: http://hdl.handle.net/20.500.11850/48103

► One of the major objectives during the development process ofnew products is to reduce costs and time to market. Increasing computational power and continuous improvements… (more)

▼ One of the major objectives during the development process ofnew products is to reduce costs and time to market. Increasing computational power and continuous improvements of modeis for internal combustion engine applications show promise with respect to replacement of some optimisation Steps by Computer simulations. A prerequisite for such a Substitution is that trends can be reasonably predictedand that calculations adequately incorporatethe physics. The flame propagation and the knock behaviour of compressed natural gas engines have been studied in the present work. The aim is to improve the physical understanding on one hand and to develop physically based modeis for cycle Simulation tools on the other hand. These modeis have been used to optimise a new engine concept which combines ultra-low emissions, high efficiency and driveability. An empirical combustion model based on experimentally determined burn rate curves has been developed to predict the engine behaviour for a wide ränge of operating conditions. It was found that global qualitative trends can be predicted quite well. Some relevant parameters characterising the combustion process - the crank angle at 5% burned, the crank angle at 50% burned and the burn duration defined as 5% to 90% burned - have been computed and compared with experimental data. The limitations of such a model have been shown by evaluating this model for a different combustion chamber geometry and various operating conditions. Therefore,a new model based on physical formulations has been developed. The phenomenological combustion model dedicated to compressed natural gas engines developed in this work can be used for projections and addionally to support the understanding of experimental results. A characteristic mean flame front area has been defined by applying some submodels describing the laminar flame speed, the turbulent flame speed and the turbulence intensity. Furthermore, the expansion factor describing the flame propagation due to the ratio of the densities of burned and unburned mixture has been considered. Good agreements between experimental data and computedresults have been observed by applying this model to a different combustion chamber geometry. The characteristic mean flame front area was redefined for these new geometrical properties. It was shown, that the new flame front area can be approximated based on considerations concerning flame propagation and based on the known mean flame front area. Research and development activities often focus on increasing the efficiency of spark ignited engines, but many modifications leading to higher engine efficiency in part load operation lead to higher risk of knock occurrence at füll load operation. These contradictory requirements clearly indicate the necessity of accurate physical formulations of the knock phenomena. The model developed in this work is based on a one step chemistry approach leading to the so called knock integral method. Due to the varying gas composition of compressed natural gas five well-defined… Advisors/Committee Members: Spicher, Ulrich, Boulouchos, Konstantinos.

Subjects/Keywords: COMBUSTION (INTERNAL COMBUSTION ENGINES); GASMASCHINEN, GASMOTOREN (WÄRMEKRAFTMASCHINEN); FRÜHZÜNDUNG, KLOPFEN, SPÄTZÜNDUNG (VERBRENNUNGSMOTOREN); COMPRESSED GASES (GAS TECHNOLOGY); SPONTANE REAKTIONEN, EXPLOSIONEN UND VERBRENNUNGEN (CHEMISCHE KINETIK); ZÜNDUNG + ZÜNDTEMPERATUR + ZÜNDEIGENSCHAFTEN (BRENNSTOFFTECHNOLOGIE); KOMPRIMIERTE GASE (GASTECHNOLOGIE); SPONTANEOUS REACTIONS, EXPLOSIONS AND COMBUSTION (CHEMICAL KINETICS); AUTO-OXIDATION + SELF-IGNITION + FLAMMABILITY + FLASH POINT (CHEMICAL KINETICS); VERBRENNUNGSKRAFTMASCHINEN (WÄRMEKRAFTMASCHINEN); MODELLRECHNUNG IN TECHNIK UND INGENIEURWESEN; PREMATURE IGNITION, KNOCK, DELAYED IGNITION (INTERNAL COMBUSTION ENGINES); VERBRENNUNG (VERBRENNUNGSMOTOREN); COMPUTATIONAL FLUID DYNAMICS (FLUIDMECHANIK); MATHEMATICAL MODELING IN ENGINEERING AND TECHNOLOGY; AUTOOXIDATION + SELBSTZÜNDUNG + ENTFLAMMBARKEIT + FLAMMPUNKT (CHEMISCHE KINETIK); INTERNAL COMBUSTION ENGINES (HEAT ENGINES); AEROTHERMODYNAMIK; AEROTHERMODYNAMICS; COMPUTATIONAL FLUID DYNAMICS (FLUID MECHANICS); IGNITION PROPERTIES + IGNITION TEMPERATURE (FUEL TECHNOLOGY); RECIPROCATING GAS ENGINES (HEAT ENGINES); info:eu-repo/classification/ddc/620; Engineering & allied operations

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Lämmle, C. (2005). Numerical and experimental study of flame propagation and knock in a compressed natural gas engine. (Doctoral Dissertation). ETH Zürich. Retrieved from http://hdl.handle.net/20.500.11850/48103

Chicago Manual of Style (16^th Edition):

Lämmle, Christian. “Numerical and experimental study of flame propagation and knock in a compressed natural gas engine.” 2005. Doctoral Dissertation, ETH Zürich. Accessed December 13, 2019. http://hdl.handle.net/20.500.11850/48103.

MLA Handbook (7^th Edition):

Lämmle, Christian. “Numerical and experimental study of flame propagation and knock in a compressed natural gas engine.” 2005. Web. 13 Dec 2019.

Vancouver:

Lämmle C. Numerical and experimental study of flame propagation and knock in a compressed natural gas engine. [Internet] [Doctoral dissertation]. ETH Zürich; 2005. [cited 2019 Dec 13]. Available from: http://hdl.handle.net/20.500.11850/48103.

Council of Science Editors:

Lämmle C. Numerical and experimental study of flame propagation and knock in a compressed natural gas engine. [Doctoral Dissertation]. ETH Zürich; 2005. Available from: http://hdl.handle.net/20.500.11850/48103

ETH Zürich

455. Koch, Thomas. Numerischer Beitrag zur Charakterisierung und Vorausberechnung der Gemischbildung und Verbrennung in einem direkteingespritzten, strahlgeführten Ottomotor.

Degree: 2002, ETH Zürich

URL: http://hdl.handle.net/20.500.11850/86312

Subjects/Keywords: COMBUSTION (INTERNAL COMBUSTION ENGINES); EINSPRITZANLAGEN (VERBRENNUNGSMOTOREN); RECIPROCATING CARBURETTOR ENGINES, OTTO ENGINES (INTERNAL COMBUSTION ENGINES); STICKSTOFFOXIDE (UMWELTSCHADSTOFFE); FUEL SUPPLY + CARBURETION (INTERNAL COMBUSTION ENGINES); GAS-FLÜSSIGKEITSGEMISCHE/EMULSIONEN (FLUIDDYNAMIK); FUEL INJECTION FOR OTTO ENGINES (INTERNAL COMBUSTION ENGINES); MODELLRECHNUNG IN TECHNIK UND INGENIEURWESEN; VERBRENNUNG (VERBRENNUNGSMOTOREN); COMPUTATIONAL FLUID DYNAMICS (FLUIDMECHANIK); MATHEMATICAL MODELING IN ENGINEERING AND TECHNOLOGY; FUEL INJECTION DEVICES (INTERNAL COMBUSTION ENGINES); BRENNSTOFFZUFUHR + GEMISCHBILDUNG (VERBRENNUNGSMOTOREN); ABGASRÜCKFÜHRUNG, AGR (VERBRENNUNGSMOTOREN); DIREKTEINSPRITZENDE OTTOMOTOREN (VERBRENNUNGSMOTOREN); COMPUTATIONAL FLUID DYNAMICS (FLUID MECHANICS); MIXED-PHASE FLOW, FOAMS AND EMULSIONS (FLUID DYNAMICS); OTTOMOTOREN, BENZINMOTOREN (VERBRENNUNGSMOTOREN); NITROGEN OXIDES (ENVIRONMENTAL POLLUTANTS); EXHAUST GAS RECIRCULATION, EGR (INTERNAL COMBUSTION ENGINES); info:eu-repo/classification/ddc/620; info:eu-repo/classification/ddc/530; Engineering & allied operations; Physics

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Koch, T. (2002). Numerischer Beitrag zur Charakterisierung und Vorausberechnung der Gemischbildung und Verbrennung in einem direkteingespritzten, strahlgeführten Ottomotor. (Doctoral Dissertation). ETH Zürich. Retrieved from http://hdl.handle.net/20.500.11850/86312

Chicago Manual of Style (16^th Edition):

Koch, Thomas. “Numerischer Beitrag zur Charakterisierung und Vorausberechnung der Gemischbildung und Verbrennung in einem direkteingespritzten, strahlgeführten Ottomotor.” 2002. Doctoral Dissertation, ETH Zürich. Accessed December 13, 2019. http://hdl.handle.net/20.500.11850/86312.

MLA Handbook (7^th Edition):

Koch, Thomas. “Numerischer Beitrag zur Charakterisierung und Vorausberechnung der Gemischbildung und Verbrennung in einem direkteingespritzten, strahlgeführten Ottomotor.” 2002. Web. 13 Dec 2019.

Vancouver:

Koch T. Numerischer Beitrag zur Charakterisierung und Vorausberechnung der Gemischbildung und Verbrennung in einem direkteingespritzten, strahlgeführten Ottomotor. [Internet] [Doctoral dissertation]. ETH Zürich; 2002. [cited 2019 Dec 13]. Available from: http://hdl.handle.net/20.500.11850/86312.

Council of Science Editors:

Koch T. Numerischer Beitrag zur Charakterisierung und Vorausberechnung der Gemischbildung und Verbrennung in einem direkteingespritzten, strahlgeführten Ottomotor. [Doctoral Dissertation]. ETH Zürich; 2002. Available from: http://hdl.handle.net/20.500.11850/86312

University of Dundee

456. Kokkalis, Efstratios. Fluid dynamic assessments of spiral flow induced by vascular grafts.

Degree: PhD, 2014, University of Dundee

URL: http://hdl.handle.net/10588/5b96492f-983f-4baa-8e48-20da6939e65c

► Peripheral vascular grafts are used for the treatment of peripheral arterial disease and arteriovenous grafts for vascular access in end stage renal disease. The development… (more)

▼ Peripheral vascular grafts are used for the treatment of peripheral arterial disease and arteriovenous grafts for vascular access in end stage renal disease. The development of neo-intimal hyperplasia and thrombosis in the distal anastomosis remains the main reason for occlusion in that region. The local haemodynamics produced by a graft in the host vessel is believed to significantly affect endothelial function. Single spiral flow is a normal feature in medium and large sized vessels and it is induced by the anatomical structure and physiological function of the cardiovascular system. Grafts designed to generate a single spiral flow in the distal anastomosis have been introduced in clinical practice and are known as spiral grafts. In this work, spiral peripheral vascular and arteriovenous grafts were compared with conventional grafts using ultrasound and computational methods to identify their haemodynamic differences. Vascular-graft flow phantoms were developed to house the grafts in different surgical configurations. Mimicking components, with appropriate acoustic properties, were chosen to minimise ultrasound beam refraction and distortion. A dual-beam two-dimensional vector Doppler technique was developed to visualise and quantify vortical structures downstream of each graft outflow in the cross-flow direction. Vorticity mapping and measurements of circulation were acquired based on the vector Doppler data. The flow within the vascular-graft models was simulated with computed tomography based image-guided modelling for further understanding of secondary flow motions and comparison with the experimental results. The computational assessments provided a three-dimensional velocity field in the lumen of the models allowing a range of fluid dynamic parameters to be predicted. Single- or double-spiral flow patterns consisting of a dominant and a smaller vortex were detected in the outflow of the spiral grafts. A double- triple- or tetra-spiral flow pattern was found in the outflow of the conventional graft, depending on model configuration and Reynolds number. These multiple-spiral patterns were associated with increased flow stagnation, separation and instability, which are known to be detrimental for endothelial behaviour. Increased in-plane mixing and wall shear stress, which are considered atheroprotective in normal vessels, were found in the outflow of the spiral devices. The results from the experimental approach were in agreement with those from the computational approach. This study applied ultrasound and computational methods to vascular-graft phantoms in order to characterise the flow field induced by spiral and conventional peripheral vascular and arteriovenous grafts. The results suggest that spiral grafts are associated with advanced local haemodynamics that may protect endothelial function and thereby may prevent their outflow anastomosis from neo-intimal hyperplasia and thrombosis. Consequently this work supports the hypothesis that spiral grafts may decrease outflow stenosis and hence improve patency…

Subjects/Keywords: 617.4; Spiral flow; Disturbed flow; Double spiral flow; Dean flow; Multiple spiral flow; Secondary flow motions; Flow stagnation; Flow separation; Flow instability; Peripheral arterial disease; End stage renal disease; Haemodialysis; Haemodynamics; Vascular graft; Prosthetic graft; Bypass graft; Arteriovenous graft; Peripheral vascular graft; AV graft; PV graft; Spiral flow graft; Spiral graft; Flow modification graft; Doppler ultrasound; Colour Doppler; Vector Doppler ultrasound; Flow phantom; Fluid dynamics; Fluid mechanics; Computational fluid dynamics; 31. Polyvinyl alcohol cryogel; Vessel mimic; Vessel mimicking tubing; Tissue mimic; Tissue mimicking material; Blood mimic; Blood mimicking material; Dual beam vector Doppler; Vorticity; Circulation; Velocity; Tangential velocity; Perpendicular velocity; In-plane velocity; Neo-intimal hyperplasia; Thrombosis; Vortical structures; Flow mixing; In-plane mixing; Image guided modelling; Wall shear stress; Helicity; Pressure drop

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Kokkalis, E. (2014). Fluid dynamic assessments of spiral flow induced by vascular grafts. (Doctoral Dissertation). University of Dundee. Retrieved from http://hdl.handle.net/10588/5b96492f-983f-4baa-8e48-20da6939e65c

Chicago Manual of Style (16^th Edition):

Kokkalis, Efstratios. “Fluid dynamic assessments of spiral flow induced by vascular grafts.” 2014. Doctoral Dissertation, University of Dundee. Accessed December 13, 2019. http://hdl.handle.net/10588/5b96492f-983f-4baa-8e48-20da6939e65c.

MLA Handbook (7^th Edition):

Kokkalis, Efstratios. “Fluid dynamic assessments of spiral flow induced by vascular grafts.” 2014. Web. 13 Dec 2019.

Vancouver:

Kokkalis E. Fluid dynamic assessments of spiral flow induced by vascular grafts. [Internet] [Doctoral dissertation]. University of Dundee; 2014. [cited 2019 Dec 13]. Available from: http://hdl.handle.net/10588/5b96492f-983f-4baa-8e48-20da6939e65c.

Council of Science Editors:

Kokkalis E. Fluid dynamic assessments of spiral flow induced by vascular grafts. [Doctoral Dissertation]. University of Dundee; 2014. Available from: http://hdl.handle.net/10588/5b96492f-983f-4baa-8e48-20da6939e65c

University of Dundee

457. Kokkalis, Efstratios. Fluid dynamic assessments of spiral flow induced by vascular grafts.

Degree: PhD, 2014, University of Dundee

URL: https://discovery.dundee.ac.uk/en/studentTheses/5b96492f-983f-4baa-8e48-20da6939e65c ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633772

► Peripheral vascular grafts are used for the treatment of peripheral arterial disease and arteriovenous grafts for vascular access in end stage renal disease. The development… (more)

▼ Peripheral vascular grafts are used for the treatment of peripheral arterial disease and arteriovenous grafts for vascular access in end stage renal disease. The development of neo-intimal hyperplasia and thrombosis in the distal anastomosis remains the main reason for occlusion in that region. The local haemodynamics produced by a graft in the host vessel is believed to significantly affect endothelial function. Single spiral flow is a normal feature in medium and large sized vessels and it is induced by the anatomical structure and physiological function of the cardiovascular system. Grafts designed to generate a single spiral flow in the distal anastomosis have been introduced in clinical practice and are known as spiral grafts. In this work, spiral peripheral vascular and arteriovenous grafts were compared with conventional grafts using ultrasound and computational methods to identify their haemodynamic differences. Vascular-graft flow phantoms were developed to house the grafts in different surgical configurations. Mimicking components, with appropriate acoustic properties, were chosen to minimise ultrasound beam refraction and distortion. A dual-beam two-dimensional vector Doppler technique was developed to visualise and quantify vortical structures downstream of each graft outflow in the cross-flow direction. Vorticity mapping and measurements of circulation were acquired based on the vector Doppler data. The flow within the vascular-graft models was simulated with computed tomography based image-guided modelling for further understanding of secondary flow motions and comparison with the experimental results. The computational assessments provided a three-dimensional velocity field in the lumen of the models allowing a range of fluid dynamic parameters to be predicted. Single- or double-spiral flow patterns consisting of a dominant and a smaller vortex were detected in the outflow of the spiral grafts. A double- triple- or tetra-spiral flow pattern was found in the outflow of the conventional graft, depending on model configuration and Reynolds number. These multiple-spiral patterns were associated with increased flow stagnation, separation and instability, which are known to be detrimental for endothelial behaviour. Increased in-plane mixing and wall shear stress, which are considered atheroprotective in normal vessels, were found in the outflow of the spiral devices. The results from the experimental approach were in agreement with those from the computational approach. This study applied ultrasound and computational methods to vascular-graft phantoms in order to characterise the flow field induced by spiral and conventional peripheral vascular and arteriovenous grafts. The results suggest that spiral grafts are associated with advanced local haemodynamics that may protect endothelial function and thereby may prevent their outflow anastomosis from neo-intimal hyperplasia and thrombosis. Consequently this work supports the hypothesis that spiral grafts may decrease outflow stenosis and hence improve patency…

Subjects/Keywords: 617.4; Spiral flow; Disturbed flow; Double spiral flow; Dean flow; Multiple spiral flow; Secondary flow motions; Flow stagnation; Flow separation; Flow instability; Peripheral arterial disease; End stage renal disease; Haemodialysis; Haemodynamics; Vascular graft; Prosthetic graft; Bypass graft; Arteriovenous graft; Peripheral vascular graft; AV graft; PV graft; Spiral flow graft; Spiral graft; Flow modification graft; Doppler ultrasound; Colour Doppler; Vector Doppler ultrasound; Flow phantom; Fluid dynamics; Fluid mechanics; Computational fluid dynamics; 31. Polyvinyl alcohol cryogel; Vessel mimic; Vessel mimicking tubing; Tissue mimic; Tissue mimicking material; Blood mimic; Blood mimicking material; Dual beam vector Doppler; Vorticity; Circulation; Velocity; Tangential velocity; Perpendicular velocity; In-plane velocity; Neo-intimal hyperplasia; Thrombosis; Vortical structures; Flow mixing; In-plane mixing; Image guided modelling; Wall shear stress; Helicity; Pressure drop

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Kokkalis, E. (2014). Fluid dynamic assessments of spiral flow induced by vascular grafts. (Doctoral Dissertation). University of Dundee. Retrieved from https://discovery.dundee.ac.uk/en/studentTheses/5b96492f-983f-4baa-8e48-20da6939e65c ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633772

Chicago Manual of Style (16^th Edition):

Kokkalis, Efstratios. “Fluid dynamic assessments of spiral flow induced by vascular grafts.” 2014. Doctoral Dissertation, University of Dundee. Accessed December 13, 2019. https://discovery.dundee.ac.uk/en/studentTheses/5b96492f-983f-4baa-8e48-20da6939e65c ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633772.

MLA Handbook (7^th Edition):

Kokkalis, Efstratios. “Fluid dynamic assessments of spiral flow induced by vascular grafts.” 2014. Web. 13 Dec 2019.

Vancouver:

Kokkalis E. Fluid dynamic assessments of spiral flow induced by vascular grafts. [Internet] [Doctoral dissertation]. University of Dundee; 2014. [cited 2019 Dec 13]. Available from: https://discovery.dundee.ac.uk/en/studentTheses/5b96492f-983f-4baa-8e48-20da6939e65c ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633772.

Council of Science Editors:

Kokkalis E. Fluid dynamic assessments of spiral flow induced by vascular grafts. [Doctoral Dissertation]. University of Dundee; 2014. Available from: https://discovery.dundee.ac.uk/en/studentTheses/5b96492f-983f-4baa-8e48-20da6939e65c ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633772

ETH Zürich

458. Barroso Raya, Gabriel. Chemical kinetic mechanism reduction, multizone and 3D-CRFD modelling of homgeneous charge compression ignition engines.

Degree: 2006, ETH Zürich

URL: http://hdl.handle.net/20.500.11850/149129

Subjects/Keywords: VERBRENNUNGSKRAFTMASCHINEN (WÄRMEKRAFTMASCHINEN); ZERSTÄUBERDÜSEN (FLUIDDYNAMIK); AEROTHERMODYNAMIK; KOMPRIMIERTE GASE (GASTECHNOLOGIE); ZÜNDUNG + ZÜNDTEMPERATUR + ZÜNDEIGENSCHAFTEN (BRENNSTOFFTECHNOLOGIE); VERBRENNUNG (VERBRENNUNGSMOTOREN); SPONTANE REAKTIONEN, EXPLOSIONEN UND VERBRENNUNGEN (CHEMISCHE KINETIK); AUTOOXIDATION + SELBSTZÜNDUNG + ENTFLAMMBARKEIT + FLAMMPUNKT (CHEMISCHE KINETIK); ABGASEMISSIONEN; RAUCH UND RUSS (LUFTVERUNREINIGUNG); COMPUTATIONAL FLUID DYNAMICS (FLUIDMECHANIK); MODELLRECHNUNG IN TECHNIK UND INGENIEURWESEN; INTERNAL COMBUSTION ENGINES (HEAT ENGINES); SPRAY NOZZLES + ATOMIZERS (FLUID DYNAMICS); AEROTHERMODYNAMICS; COMPRESSED GASES (GAS TECHNOLOGY); IGNITION PROPERTIES + IGNITION TEMPERATURE (FUEL TECHNOLOGY); COMBUSTION (INTERNAL COMBUSTION ENGINES); SPONTANEOUS REACTIONS, EXPLOSIONS AND COMBUSTION (CHEMICAL KINETICS); AUTO-OXIDATION + SELF-IGNITION + FLAMMABILITY + FLASH POINT (CHEMICAL KINETICS); WASTE GAS EMISSION; SMOKE AND SOOT (AIR POLLUTION); COMPUTATIONAL FLUID DYNAMICS (FLUID MECHANICS); MATHEMATICAL MODELING IN ENGINEERING AND TECHNOLOGY; info:eu-repo/classification/ddc/620; info:eu-repo/classification/ddc/540; Engineering & allied operations; Chemistry

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APA (6^th Edition):

Barroso Raya, G. (2006). Chemical kinetic mechanism reduction, multizone and 3D-CRFD modelling of homgeneous charge compression ignition engines. (Doctoral Dissertation). ETH Zürich. Retrieved from http://hdl.handle.net/20.500.11850/149129

Chicago Manual of Style (16^th Edition):

Barroso Raya, Gabriel. “Chemical kinetic mechanism reduction, multizone and 3D-CRFD modelling of homgeneous charge compression ignition engines.” 2006. Doctoral Dissertation, ETH Zürich. Accessed December 13, 2019. http://hdl.handle.net/20.500.11850/149129.

MLA Handbook (7^th Edition):

Barroso Raya, Gabriel. “Chemical kinetic mechanism reduction, multizone and 3D-CRFD modelling of homgeneous charge compression ignition engines.” 2006. Web. 13 Dec 2019.

Vancouver:

Barroso Raya G. Chemical kinetic mechanism reduction, multizone and 3D-CRFD modelling of homgeneous charge compression ignition engines. [Internet] [Doctoral dissertation]. ETH Zürich; 2006. [cited 2019 Dec 13]. Available from: http://hdl.handle.net/20.500.11850/149129.

Council of Science Editors:

Barroso Raya G. Chemical kinetic mechanism reduction, multizone and 3D-CRFD modelling of homgeneous charge compression ignition engines. [Doctoral Dissertation]. ETH Zürich; 2006. Available from: http://hdl.handle.net/20.500.11850/149129

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