SIFCON was first reported in 1984 and showed excellent potential as a structural material. Applications, however, have been slow to emerge. The aim of this investigation was to simplify the production of SIFCON and to identify practical applications. A direct infiltration test was developedt o assessth e effect of materials and admixtures on the infiltration properties of cement based slurries. A slurry was designed which could infiltrate fibre beds containing up to 16 percent by volume of fibres without the aid of vibration. To achieve this, novel use was made of viscosity modifying admixtures in conjunction with superplasticisers. The mechanical properties of the SIFCON produced using the new slurry were investigated in terms of compression and flexure. It was found that, while the outstanding parameters, in terms of strength and ductility, associated with SIFCON were apparent, the resulting material was strongly anisotropic. The compressive modulus of elasticity was found to be significantly lower than would be expected for conventional concrete of similar strength. Pull-out tests showed that the bond performance was ductile for ribbed reinforcing bars embedded in SIFCON, however, the dependenceo n fibre orientation was highlighted. SIFCON sections were successfully incorporated into reinforced concrete beams and the production of these beams demonstrated the benefits of the self compacting technique. The results of third point loading tests highlighted problems relating to the modulus of rupture of SIFCON, and the difficulties faced when introducing it into reinforced concrete structures. It was also found that the use of SIFCON in horizontally cast beams was inefficient in the compression zone. It is expected that the advances made in the development of the production process will lead to increased acceptance of SIFCON and that new applications will emerge.

This research explores the minimizing of cracks in the fabrication of carbon-infiltrated carbon nanotube (CI-CNT) forests on cylindrical rods for the purposes of creating a CI-CNT coronary stent. It is a continuation of the work begun by Jones [1] and Skousen [2] whose work included the creation of a feasible CI-CNT coronary stent on a planar surface. The current research was performed in two parts: 1) growth on the whole circumference of the rod for ~20mm in length and 2) growth in lines and patterns. Experiments were done on either a 309 or 304 stainless steel rod ~3mm in diameter.The following parameters were used for growth on the whole circumference of the rod: a 80nm alumina diffusion barrier, 1.3 or 7nm of iron as a catalyst layer for CNT growth and a growth time of 1 or 15 min. Cracking is observed on most samples. Area fraction of cracking is shown to be minimized with 7nm of iron and and 1 min growth time. The number of cracks was minimized with the 7nm of iron and 15 min growth time. The height of the CI-CNT forest, which is strongly influenced by the thickness of the iron layer and growth time, is shown to be a possible positive contributor to the area fraction of cracking. Level of carbon infiltration and rate of cooling were also included in the parameters of the study as possible contributors to the amount of cracking however no correlation was found to either of these factors. The second study maintained 80nm of alumina and used 7nm of iron and 10 min of growth time. Line angles parallel, at 7°, at 45° and perpendicular to the axis of the rod and line widths from 109µm to 500µm were studied. Line widths from 500µm to 1090µm were also included in the study of patterned lines perpendicular to the axis of the rod. Cracking was eliminated in the parallel and 7° lines. Cracking in the 45° lines was intermittent and significantly less than the cracking seen on the whole circumference. For the lines perpendicular to the axis, the uncracked arc length was calculated to be an average of 414µm with a standard deviation of 67µm. The uncracked arc length showed no correlation to the line width. A final aspect of this second study observed the cracking in a modification of the planar stent pattern created by Jones. The pattern was modified in to allow for patterning on the rod. The critical dimension maximums of the parent pattern were maintained. The experimental results showed that a continual CI-CNT forest could be fabricated to the minimum expected height of 150µm, a maximum width of 542µm and at the expected angle of 7° with minimal to no cracking.

BACKGROUND: Polymer-infiltrated zirconia ceramic, benefiting from the synergistic effect of the ceramic matrix providing strength and the polymer enhancing toughness, has the potential to mimic the structure of natural teeth in its optical and mechanical properties. OBJECTIVE: To determine the effect of additives and various sintering temperatures on the optical and mechanical properties of zirconia ceramic matrix composites. MATERIALS AND METHODS: Groups consisted of unmodified zirconia powder, and zirconia modified with porcelain and porogens to form the porous ceramic matrix. Three types of Tosoh zirconia powder, TZ-3YSB-E, Zpex, and Zpex Smile, were used to fabricate porous blocks. Zirconia powder and porcelain powder were ball-milled separately. Zirconia powder was dry pressed and then cold isostatic pressed. The blocks were sintered at 1000 and 1150 ºC and sectioned into discs (n=10). For zirconia with additives groups, 10% of Titankeramik and 5% of PEG8000 were mixed to zirconia powder using a high-speed mixer. The zirconia blocks were pressed and sintered at 1000, 1150, 1200 and 1300 ℃, and sectioned into discs (n=10). Porous discs were treated with a 10% wt solution of 10-MDP for 4 hours and then dried in a vacuum oven for 24 hours. TEGDMA-UDMA resin monomers were infiltrated into discs and cured at 90°C under pressure. Polymer-infiltrated ceramics specimens were polished to 1.5 mm in thickness. Optical properties were determined with an X-rite spectrophotometer. Biaxial flexural strength and Vickers indentation tests were performed using an Instron universal mechanical tester. Vickers hardness and indentation fracture toughness values were calculated by measuring the indent dimensions under FESEM, in addition to microstructure assessment. Statistical analyses were performed using computer software, Microsoft Excel 2016 and JMP Pro 15. RESULTS: This study revealed that the type of zirconia powder utilized for the fabrication of porous ceramics for polymer-infiltration structures did not significantly influence their optical properties. Mean values of fully sintered zirconia showed significantly higher biaxial flexural strength (628.5-1277.4 MPa) than polymer-infiltrated groups (105.4-433.6 MPa), with P-3Y1150 achieving the highest value. Higher pre-sintering temperature from 1000 ℃ to 1150 ℃ led to enhanced biaxial flexural strength for polymer-infiltrated pure zirconia specimens, with values rising from 126.5-158.2 MPa to 243.4-433.6 MPa. Adding porcelain and porogens did not significantly affect the optical or specific mechanical properties, such as biaxial flexural strength and Vickers hardness, despite increasing the sintering temperature to 1300 ℃. Nevertheless, a significant increase in indentation fracture toughness was noted with ZPTKPEG1200 (7.65±0.55 MPa·m1/2) and ZPTKPEG1300 (7.09±0.61 MPa·m1/2), values that were markedly higher than those in all control groups of fully sintered zirconia (p<0.001). Sintering temperature was found to be a key determinant in influencing the ceramic matrix's microstructure, porosity, and density, as well as the biaxial flexural strength, Vickers hardness, and indentation fracture toughness of polymer-infiltrated zirconia. While changes in temperature did not affect optical properties, and polymer infiltration did not enhance all attributes, it did substantially elevate the indentation fracture toughness in mixed zirconia samples with additives, offering a potential area for further research. CONCLUSION: The mechanical properties of polymer-infiltrated ceramics responded significantly to the sintering temperature and the type of zirconia powder utilized, most notably in the 3Y-TZSB-E group. A notable increased indentation fracture toughness was discernible when Zpex powder, mixed with additives, was subject to polymer infiltration and sintered at temperatures between 1200-1300 °C. Even though polymer infiltration and additive incorporation did not uniformly enhance all properties, a noticeable improvement in fracture toughness was observed. These findings open the door to future research, especially in potential applications of dental restorative materials that demand superior fracture toughness.

Eksperimentai buvo atliekami su bandinėliais gautais iš Madrido, Maskvos ir St.Peterburgo, tai yra su fotoniniais kristalais. Darbe buvo nagrinėta fotoninio kristalo opalo struktūrą ir optines savybes draustinės stop juostos srityje bei defektų valdymo būdai, keičiant elektrinį lauką. Nagrinėjamas elektrinio lauko poveikis defektams, stop juostai. Nustatyta, kad elektriniame lauke susikuria defektai, kuriuos galima valdyti nuo 0V iki 7V įtampos intervale. Išmatuoti defektinės modos perjungimo laikai kurie sieka 200 s, tai 10 kart greičiau nei stop juostos. / We did structural and spectroscopic studies of bulk and thin film synthetic opal. Demonstrate that the photonic crystal, opal have defects, but these defects may be "good" when use it to control light in stop band.

Made available in DSpace on 2016-12-23T14:08:14Z (GMT). No. of bitstreams: 1 Capa, Cap 1 e Cap 2 ate secao 2-2-1-9.pdf: 1005078 bytes, checksum: 68579a03ea37b6d408ea44008ec9ad0f (MD5) Previous issue date: 2010-12-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Este trabalho tem o objetivo de avaliar uma possível relação entre as propriedades mecânicas calculadas a partir dos dados de micropenetração instrumentada e o comportamento sob desgaste microabrasivo dos compósitos à base de tungstênio (W) infiltrados por latão, usados em coroas diamantadas utilizadas em sondagem mineral. As amostras dos compósitos de tungstênio foram sinterizadas com combinações de diferentes tamanhos de partículas W e adições de ligas à base de outros elementos, além de adições de abrasivos secundários (SiC). Após a preparação metalográfica, as amostras foram analisadas em um micropenetrador instrumentado com um pen etrador do tipo Vickers. As fases foram penetradas com uma carga de 30 mN, exceto o carbeto de silício, com carga de 250 mN. As curvas geradas a cada penetração permitiram calcular a microdureza e o módulo de elasticidade para cada fase. Estes resultados foram comparados com os coeficientes de desgaste microabrasivo dimensionais obtidos em um trabalho anterior, através de ensaios de microabrasão com lamas abrasivas à base de carbeto de silício, sílica e hematita, efetuados com equipamento do tipo Calowear. Foi observada uma diminuição na microdureza conforme o tamanho dos grãos de tungstênio aumenta. Para a lama abrasiva contendo SiC, uma diminuição no coeficiente de desgaste microabrasivo se seguiu à diminuição na microdureza do tungstênio. O oposto foi observado com a lama de SiO2, enquanto, para a lama de Fe2O3, nenhuma correlação clara foi obtida. Também é importante dizer que o efeito da dureza do latão infiltrado (fase aglutinante) tornou-se mais significativa nos ensaios com as pastas de SiO2 e de Fe2O3. Quando as ligas à base de outros elementos são adicionadas, para o abrasivo SiC, o aumento da plasticidade do latão aumenta o desgaste, porque as deformações plásticas são aumentadas, levando em consideração a relação Habr./Hfase muito alta. A plasticidade da fase W parece não interferir no desgaste. Ocorre o contrário para o abrasivo SiO2. Para ambos os abrasivos, o cobre adicionado aumenta a fração volumétrica de fase macia , proporcionando um desgaste ainda maior. Para o abrasivo Fe2O3, o aumento na plasticidade do latão aumenta o coeficiente de desgaste, pois leva a indentações maiores, ou seja, a maiores deformações plásticas. Dependendo do tipo do abrasivo, os mecanismos observados foram riscamento e rolamento de partículas (múltiplas indentações), além da ocorrência de ambos simultaneamente, embora dissociados / This work intends to evaluate a possible relationship between the mechanical properties calculated from instrumented microindentation data and the microabrasive wear behavior of infiltrated tungsten (W) composites used in impregnated diamond bits for rock drilling. Specimens of brass-infiltrated W composites were sintered with combinations of different W particle sizes, and additions of alloys based on other elements, as well as additions of secondary abrasives. After metallographic preparation, the specimens were analyzed in an instrumented microindenter with a Vickers indenter. All phases were indented with a load of 30 mN, except the silicon carbide, with a load of 250 mN. The indentation curves allowed the calculation of microhardness and Young s modulus for each phase. Those results were compared with dimensional microabrasive wear coefficients obtained in a previous work, by testing microabrasion with abrasive slurries based on silicon carbide, silica and hematite, performed with Calower equipment. It was observed a decrease in microhardness as the tungsten grains size increase. For the SiC abrasive slurry, a decrease in microabrasive wear coefficient followed the decrease in tungsten microhardness. The opposite was observed with the SiO2 slurry, whereas, for the Fe2O3 slurry, no clear correlation was obtained. It is also important to say that the effect of infiltrated brass (binder phase) hardness became more significant in the tests with the SiO2 and Fe2O3 slurries. When the alloys based on other elements are added, to the SiC abrasive, the increase of the brass plasticity increases its wear, because the plastic deformations are increased, taking into account the very high Habr./Hphase relation. The plasticity of the W phase seems not to interfere in wear. The opposite is true for the SiO2 abrasive. For both abrasives, the copper added increases the "soft" phase volumetrical fraction, providing an additional wear. For the Fe2O3 abrasive, the increase in the brass plasticity increases the wear coefficient, since it leads to larger indentations, i. e., to larger plastic deformations. Depending on the abrasive type, the observed mechanisms were grooving and particles rolling (multiple indentations), besides the occurrence of both simultaneously, although, dissociated

Submitted by Maike Costa (maiksebas@gmail.com) on 2017-03-21T13:19:09Z No. of bitstreams: 1 arquivototal.pdf: 2398658 bytes, checksum: 37469752b2f4c25b709db170a9ae08b0 (MD5) / Made available in DSpace on 2017-03-21T13:19:09Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2398658 bytes, checksum: 37469752b2f4c25b709db170a9ae08b0 (MD5) Previous issue date: 2014-06-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The transport of materials trough dental enamel has been regarded as dependent on diffusion which doesn´t infiltrate the nanopores of normal dental enamel normal, being these materials considered as above the threshold for enamel nanopores (MATEN). In this in vitro study, applied the electrokinetic flow (EKF) to infiltrated the MATEN into the dental enamel pores mature of unerupted permanent human teeth. It were tested an aqueous solutions with refractive index of 1.56 (Thoulet’s solution) by 5h and a infiltrant resin ICON® by three different times (1; 1,5 and 2 h), both with pH higher than the critical pH of enamel, applying 5V in both cases. Dental enamel ground sections were mounted on customized microfluidic chips made of poly-methyl-siloxane and submitted to EKF. A pre-infiltration with 1 mM KCl solution by 2 h and 1V. Three samples were infiltrated by 1.56 Thoulet´s solution and eight samples were infiltrated using infiltrant resin. Histological sites (n = 30) in Thoulet´s group were analyzed for water birefringence before and after infiltrated. The sample of resin group were subsequently exposed to in vitro demineralization by 192h. The depth of hybrid layer was analyzed by fluorescence and polarizing microscopy. The analysis of mineral volume by radiomicrography was performed in infiltrated histological sites (n = 30) and not infiltrated histological sites (n = 30), before the infiltrated and after demineralization, always hydrated. The negative birefringence of histological points (n = 30) in water, before infiltration of Thoulet’s solution (mean of -22.47 x 10-4) was significantly lower than after the infiltrated of Thoulet’s solution 1.56 (mean of – 51.7 x 10-4) (p < 0.00001; ANOVA; effect size = 6.69). Depth of enamel hybrid layer ranged for 640 m to 1430 m (mean of 760 m). The hydrated minerals volumes of infiltrated parts before demineralization were similar to after demineralization (p = 0.123; T test) while the not infiltrated parts presented similar hydrated mineral volumes after demineralization (p < 0.00001; effect size = 3.263). It is concluded that EKF was successful in infiltrating MATEN in enamel pores, without enamel etching, resulting in a new hybrid layer model and a huge increase in infiltration compared to diffusion, opening new opportunities for scientific innovation and with potential clinical applications in Dentistry. / O transporte de materiais através do esmalte dentário tem sido baseado no processo de difusão, os quais não infiltram os nanoporos do esmalte dentário humano normal, uma vez que são considerados materiais com dimensões acima do limite dos poros do esmalte (MDALPE). Neste estudo, in vitro, aplicou-se o fluxo eletrocinético (FEC) para a infiltração dos MDALPE nos poros do esmalte dentário maduro de dentes humanos permanentes não irrompidos. Foram testados solução aquosa de Thoulet com índice de refração (n) = 1,56, por 5 h e resina infiltrante ICON® por três tempos diferentes (1; 1,5 e 2h), ambos com pH acima do valor crítico do esmalte, aplicando 5 V em ambos os casos. Cortes por desgaste de esmalte dental foram inseridos em chip microfluidicos customizados feitos de poli-metil-siloxano e submetidos ao FEC. Uma infiltração prévia com KCl 1mM foi realizada em cada amostra por 2 h, usando 1V. Três amostras foram infiltradas com solução Thoulet n= 1,56 e oito amostras foram infiltradas com resina infiltrante. Pontos histológicos (n = 30) do grupo da solução Thoulet foram analisados quanto à birrefringência em água antes e após a infiltração. As amostras do grupo da resina foram posteriormente submetidas à desmineralização in vitro por 192 h. A profundidade da camada híbrida foi determinada pela microscopia de fluorescência e de luz polarizada. A análise do volume mineral através da radiomicrografia foi realizada em pontos histológicos nas áreas infiltrada (n = 30) e não-infiltrada (n = 30), antes da infiltração e após a desmineralização, sempre hidratados. A birrefringência negativa de pontos histológicos (n = 30) em água, antes da infiltração da solução de Thoulet (média de -22,47 x 10-4) foi significativamente menor que a birrefringência após a infiltração com a solução de Thoulet n = 1,56 (média de -51, 7 x 10-4) (p < 0,00001, ANOVA; tamanho do efeito 6,69). A profundidade da camada híbrida no esmalte variou de 640 m a 1430 m (média de 760 m). Os volumes minerais (hidratados) dos pontos infiltrados antes da desmineralização foram similares àqueles após a desmineralização (p = 0,123; teste T pareado), enquanto os pontos não infiltrados apresentaram volumes minerais (hidratados) menores após a desmineralização (p < 0,00001; teste T; tamanho do efeito de 3,263). Conclui-se que a técnica do FEC foi aplicável, com sucesso, ao transporte de MDALPE, nos poros do esmalte, sem ataque ácido, resultando em um novo modelo de camada híbrida como também num aumento expressivo da infiltração resinosa se comparada com a difusão, abrindo novas oportunidades para inovação científica e com potencial de aplicações clínicas em odontologia.

Slurry infiltrated fiber concrete (SIFCON) was first produced in 1979 in the USA, by incorporating large amounts of steel fiber in molds to form very dense network of fibers. The network is then infiltrated by a fine liquid cement-based slurry or mortar. The steel fiber content can be as high as 30 % by volume. This percentage usually does not exceed 2 % in normal fiber reinforced concrete (FRC) for reasons related to mixing and workability. Due to its high fiber content, SIFCON demonstrates unique and superior mechanical properties in the areas of both strength and ductility. Most of previous research work on SIFCON has focused mainly on investigating the mechanical properties of this material. On the other hand, the studies carried out in the field of durability of SIFCON are quite limited. v Therefore, it seemed that it would be worth to study the various durability aspects of SIFCON. In view of the above, the objectives of this study are to investigate and provide information about durability of SIFCON, mainly permeability, resistance to chloride penetration, freezing and thawing and drying shrinkage. This information will help in providing the necessary database and knowledge about the ability of SIFCON to withstand the conditions for which it has been designed without deterioration, especially when it is intended to be used in aggressive environments The investigations included studying the effects of the following on durability of SIFCON: (i) matrix type (slurry or mortar), (ii) fiber contents (7%, 9.5%, and 12% by volume), and (iii) steel fiber geometry (hooked or crimped). The results obtained indicated that SIFCON, especially when prepared using mortar not slurry, has shown good durability characteristics in spite of its apparent high water absorption. The SIFCON made with the highest possible fiber volume fractions showed the best results. However, it was concluded that SIFCON needs to be protected with suitable low permeability overlays to ensure ideal improved performance by protecting the steel fibers exposed on the surfaces especially against chloride attack.

Studies on the behavior of steel fiber reinforced concrete (SFRC) and slurry infiltrated fibrous concrete (SIFCON) to impact loading have started in recent years. Using these relatively new materials, higher values of tensile and compressive strength can be obtained with greater fracture toughness and energy absorption capacity, and therefore they carry a considerable importance in the design of protective structures. In this thesis, computational analyses concerning impact loading effect on concrete, steel fiber reinforced concrete (SFRC) and slurry infiltrated fibrous concrete (SIFCON) are conducted by the aid of ANSYS AUTODYN 11.0.0 software. In the simulations, the importance of the concrete compressive and tensile strengths, and the fracture energy, together with the target and projectile erosion parameters, were investigated on the response of concrete target and projectile residual velocity. The obtained results of the simulation trials on concrete, SFRC and SIFCON have been compared with the experimental outcomes of three concrete, two SFRC and two SIFCON specimens in terms of deformed target crater radius, depth volume and striking projectile residual velocities. The simulation analyses have shown that, compressive as well as tensile strengths of the concrete, SFRC and SIFCON specimens are of great importance on the crater volume while erosion parameters have a significant effect on the projectile residual velocity. Simulation outcomes possess a higher accuracy for concrete simulations when comparisons are made with available experimental results. This accuracy deteriorates for SFRC and SIFCON specimens. It was further concluded that related material tests of the specimens must be available in order to obtain higher accuracy.

Die Effektivität keramischer Wärmeübertrager kann durch eine feinere Strukturierung der Oberflächen gesteigert werden. Dies kann durch die Integration textiler Urformen anstatt der konventionell im Schlickguss hergestellten gröberen Geometrien erfolgen. Für Strukturierungen in Form von wandgebundenen Halbbögen werden die Ergebnisse umfangreicher experimenteller und numerischer Untersuchungen zu den wärmetechnischen und strömungsmechanischen Eigenschaften vorgestellt. Basierend auf den Erkenntnissen der mittels numerischer Simulation durchgeführten Parameterstudie werden verschiedene Empfehlungen für eine optimierte Anordnung der Halbbögen gegeben, um das Verhältnis von Wärmeübergang zur Druckverlust zu verbessern. Die experimentellen Ergebnisse belegen die Richtigkeit der gewählten Randbedingungen und Vereinfachungen im numerischen Modell. Des Weiteren wurden die Strömungsstrukturen mit laserdiagnostischen Messmethoden umfangreich charakterisiert.

Die Effektivität keramischer Wärmeübertrager kann durch eine feinere Strukturierung der Oberflächen gesteigert werden. Dies kann durch die Integration textiler Urformen anstatt der konventionell im Schlickguss hergestellten gröberen Geometrien erfolgen. Für Strukturierungen in Form von wandgebundenen Halbbögen werden die Ergebnisse umfangreicher experimenteller und numerischer Untersuchungen zu den wärmetechnischen und strömungsmechanischen Eigenschaften vorgestellt. Basierend auf den Erkenntnissen der mittels numerischer Simulation durchgeführten Parameterstudie werden verschiedene Empfehlungen für eine optimierte Anordnung der Halbbögen gegeben, um das Verhältnis von Wärmeübergang zur Druckverlust zu verbessern. Die experimentellen Ergebnisse belegen die Richtigkeit der gewählten Randbedingungen und Vereinfachungen im numerischen Modell. Des Weiteren wurden die Strömungsstrukturen mit laserdiagnostischen Messmethoden umfangreich charakterisiert.:0 Verwendete Symbole und Formelzeichen IV 1 Einleitung 1 1.1 Motivation 1 1.2 Lösungsansatz 2 1.3 Zielstellung und Struktur der Arbeit 4 2 Stand der Technik 5 2.1 Vorwort 5 2.2 Kennzahlen zur Charakterisierung von Rekuperatoren und Wärmeüber-trageroberflächen 6 2.3 Strömungszustände und Strömungsprofile 13 2.3.1 Grenzschichten von Strömungen 13 2.3.2 Laminare Strömung zwischen zwei parallelen Platten und im Rechteckkanal 14 2.3.3 Turbulente Strömung zwischen zwei parallelen Platten 15 2.3.4 Kenngrößen, Längen- und Zeitmaße von turbulenten Strömungen 16 2.4 Umströmung von Zylindern und Wärmeübergang an Zylindern 19 2.4.1 Quer angeströmter Zylinder, Wirbelablösung und Kármánsche Wirbelstraße 19 2.4.2 Hufeisenwirbel um einen wandgebundenen Zylinder 25 2.4.3 Zylinder in Wechselwirkung miteinander und Zylinder in Tandempaarung 27 2.4.4 Quer angeströmter Zylinder parallel zu einer Wand 28 2.5 Weitere den Wärmeübergang steigernde Strukturen 29 2.5.1 Rohrbündel 30 2.5.2 Stabrippen – „pin fins“ 31 2.5.3 Zweidimensionale Rippengeometrien 33 2.5.4 Gedrehte Bleche und andere Einbauten in Rohrquerschnitten 36 2.5.5 Turbulatoren 38 2.5.6 Poröse Körper 39 2.5.7 Drähte als wärmeübergangsteigernde Struktur 40 2.6 Wärmeübertrager für Industriegasbrenner 41 3 Numerische und experimentelle Untersuchungen der neuentwickelten Wärmeübertragerstruktur 45 4 Numerische Untersuchungen bezüglich des Strömungsfelds um die Bogenstrukturen 49 4.1 Randbedingungen und Vernetzung der numerischen Simulation 49 4.2 Bemerkungen zum Turbulenzmodell 54 4.3 Validierung des numerischen Modells am leeren Kanal 59 4.4 Ergebnisse für die Grundgeometrie 63 4.5 Parameterstudie zur Anordnung und Anzahl der Bögen 70 4.5.1 Variation der Bogendichte 70 4.5.2 Variation der Anordnung der Bögen zueinander bei konstanter Bogendichte 75 4.5.3 Variation der Kanalhöhe bei konstanten Randbedingungen 78 4.5.4 Variation der Kanalhöhe bei umgekehrten Randbedingungen 80 4.5.5 Variation des Bogendurchmessers D 82 4.5.6 Bemerkung zum Anstellwinkel 83 5 Experimentelle Untersuchungen zum Wärmeübergangskoeffizienten 85 5.1 Versuchsaufbau 85 5.2 Versuchsdurchführung und Auswertung 88 5.3 Vergleich des Versuchsstandes mit Untersuchungen für Spaltströmungen 90 5.4 Referenzmessungen mit metallischen Wärmeübertragerstrukturen 93 5.4.1 Ergebnisse für die Grundgeometrie 93 5.4.2 Variation der Kanalhöhe 96 5.4.3 Variation der Kanalhöhe bei umgekehrten Randbedingungen 97 5.5 Messung mit keramischen Strukturen 98 6 Experimentelle Untersuchungen zum Strömungsverhalten 101 6.1 Versuchsaufbau 101 6.2 PIV-Messungen 104 6.2.1 Allgemeines zum Messprinzip 104 6.2.2 Messaufbau 105 6.2.3 Versuchsergebnisse 106 6.3 LDA-Messungen 111 6.3.1 Allgemeines zum Messprinzip und zur Versuchsdurchführung 111 6.3.2 Validierung des Versuchsstandes 114 6.3.3 Strömungsprofile aus der LDA-Messung 117 6.3.4 Wirbelablösung im Bogennachlauf 130 6.3.5 Skalen der Strömung 144 7 Anwendungsbeispiel: Rekuperatorbrenner 151 7.1 Brennerprototyp und Versuchsdurchführung 151 7.2 Versuchsergebnisse und Auswertung 153 8 Zusammenfassung und Ausblick 157 9 Literaturverzeichnis 161 10 Anhang 173 10.1 Messtechnik des Windkanals 173 10.2 PIV-Messtechnik 175 10.3 LDA-Messtechnik 176 10.4 Versuche mit dem Rekuperatorprototypen 177