A. Ramani, B. Nugroho, A. Busse, J. Monty, N. Hutchins, T. Jelly
Measurements of a turbulent boundary-layer developing over systematically generated roughness are acquired for friction Reynolds numbers ranging between 3000 < Ret < 6000. A set of near-Gaussian surfaces with matched amplitude parameters and specified effective slopes in streamwise and spanwise directions are synthesised using a roughness generation algorithm. Three cases are considered: (i) an isotropic surface with equal streamwise (ESx =0:34) and spanwise effective slope (ESy = 0:34); (ii) an anisotropic spanwise elongated surface with ESx = 0:34 and ESy = 0:17, and (iii) an anisotropic streamwise elongated surface with ESx = 0:17 and ESy = 0:34. The surfaces are manufactured from square sheets of acetal copolymer using an in-house CNC router. Note that surface (iii) is obtained by simply rotating surface (ii) by 90 degrees. The principal interest here is to quantify the sensitivity of the Hama roughness function to systematic changes in surface anisotropy. To this end, hot-wire anemometry measurements are acquired at three different freestream velocities under zero-pressure gradient conditions for each surface. Relative to the isotropic case, an increase in the turbulence intensity is seen in the near-wall region for the anisotropic cases. As expected, decreasing ESx leads to a lower mean momentum deficit which confirms the findings of many previous experimental and numerical studies. However, results also suggest that ESy plays an important role. Even for the mildly anisotropic case considered here, the roughness function is seen to vary by up to 15% as ESy is reduced while ESx is held constant. In addition, regions of high streamwise dispersive velocity are seen to extend further into the flow field as ESy reduces. These observations suggest that existing models for drag prediction need to be modified to account for surface anisotropy.
{"title":"The Effects of Anisotropic Surface Roughness on Turbulent Boundary-Layer Flow","authors":"A. Ramani, B. Nugroho, A. Busse, J. Monty, N. Hutchins, T. Jelly","doi":"10.14264/c251931","DOIUrl":"https://doi.org/10.14264/c251931","url":null,"abstract":"Measurements of a turbulent boundary-layer developing over systematically generated roughness are acquired for friction Reynolds numbers ranging between 3000 < Ret < 6000. A set of near-Gaussian surfaces with matched amplitude parameters and specified effective slopes in streamwise and spanwise directions are synthesised using a roughness generation algorithm. Three cases are considered: (i) an isotropic surface with equal streamwise (ESx =0:34) and spanwise effective slope (ESy = 0:34); (ii) an anisotropic spanwise elongated surface with ESx = 0:34 and ESy = 0:17, and (iii) an anisotropic streamwise elongated surface with ESx = 0:17 and ESy = 0:34. The surfaces are manufactured from square sheets of acetal copolymer using an in-house CNC router. Note that surface (iii) is obtained by simply rotating surface (ii) by 90 degrees. The principal interest here is to quantify the sensitivity of the Hama roughness function to systematic changes in surface anisotropy. To this end, hot-wire anemometry measurements are acquired at three different freestream velocities under zero-pressure gradient conditions for each surface. Relative to the isotropic case, an increase in the turbulence intensity is seen in the near-wall region for the anisotropic cases. As expected, decreasing ESx leads to a lower mean momentum deficit which confirms the findings of many previous experimental and numerical studies. However, results also suggest that ESy plays an important role. Even for the mildly anisotropic case considered here, the roughness function is seen to vary by up to 15% as ESy is reduced while ESx is held constant. In addition, regions of high streamwise dispersive velocity are seen to extend further into the flow field as ESy reduces. These observations suggest that existing models for drag prediction need to be modified to account for surface anisotropy.","PeriodicalId":369158,"journal":{"name":"Proceedings of the 22nd Australasian Fluid Mechanics Conference AFMC2020","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129681138","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bin Jiang, D. Brouzet, M. Talei, R. Gordon, Q. Cazères, B. Cuenot
{"title":"Developing boundary conditions for DNS of diluted flames in a duct","authors":"Bin Jiang, D. Brouzet, M. Talei, R. Gordon, Q. Cazères, B. Cuenot","doi":"10.14264/af14fb7","DOIUrl":"https://doi.org/10.14264/af14fb7","url":null,"abstract":"","PeriodicalId":369158,"journal":{"name":"Proceedings of the 22nd Australasian Fluid Mechanics Conference AFMC2020","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121763130","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kalen Timbs, Mehdi Khatamifar, Wenxian Lin, E. Antunes
Heat sink can effectively dissipate heat in a range of thermal applications for improved performance and reliability. Thermally conductive polymer composites show great promise in solving the overheating issue in electronic devices. This experimental study investigates the thermal performance and the flow characteristics of straight and oblique finned heat sinks made of thermally conductive polymer composites under forced convection conditions over 7 . 45 × 10 4 ≤ Re ≤ 3 . 60 × 10 5 , where Re is the Reynolds number. The heat sinks used were 3D printed using Ice9 Flex (carbon filled polymer, from TCPoly), copper filled filament (polylactic acid with 80% copper particles) and bronze filled filament (polylactic acid with 80% bronze parti-cles), respectively. Oblique fins were found to effectively reduce the thermal resistance of heat sinks, increase the convec-tive heat transfer and the inner-fin velocity which results in lower pressure drop, in comparison to straight finned heat sinks. The carbon-filled polymer (Ice9 Flex) was shown to have much superior thermal dissipation characteristics compared to metal filled filaments.
{"title":"Experimental study on the thermal performance of straight and oblique finned, polymer heat sinks","authors":"Kalen Timbs, Mehdi Khatamifar, Wenxian Lin, E. Antunes","doi":"10.14264/ee77585","DOIUrl":"https://doi.org/10.14264/ee77585","url":null,"abstract":"Heat sink can effectively dissipate heat in a range of thermal applications for improved performance and reliability. Thermally conductive polymer composites show great promise in solving the overheating issue in electronic devices. This experimental study investigates the thermal performance and the flow characteristics of straight and oblique finned heat sinks made of thermally conductive polymer composites under forced convection conditions over 7 . 45 × 10 4 ≤ Re ≤ 3 . 60 × 10 5 , where Re is the Reynolds number. The heat sinks used were 3D printed using Ice9 Flex (carbon filled polymer, from TCPoly), copper filled filament (polylactic acid with 80% copper particles) and bronze filled filament (polylactic acid with 80% bronze parti-cles), respectively. Oblique fins were found to effectively reduce the thermal resistance of heat sinks, increase the convec-tive heat transfer and the inner-fin velocity which results in lower pressure drop, in comparison to straight finned heat sinks. The carbon-filled polymer (Ice9 Flex) was shown to have much superior thermal dissipation characteristics compared to metal filled filaments.","PeriodicalId":369158,"journal":{"name":"Proceedings of the 22nd Australasian Fluid Mechanics Conference AFMC2020","volume":"77 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115172343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study aims to investigate the sound inducing fluid dynamic behaviour of a pipe section with a leak for two different leak configurations and the influence of fluid dynamic changes on acoustic emission (AE) signal features. It is found that turbulence and cavitation occur at the leak vicinity under high pressure. The intensity of these fluid dynamic changes is strongly related to the severity of the leakage. The AE responses to these occurrences are symptomatic to the leak severity. Interestingly, the cavitation is responsible for increasing AE RMS value, indicating severity of the damage.
{"title":"Investigation of Sound Inducing Fluid Dynamics at Pipe Leak and It's Influence on Acoustic Emission Signals","authors":"F. Zohora, D. Holmes, M. Cholette, Yuantong T. Gu","doi":"10.14264/4ce35f0","DOIUrl":"https://doi.org/10.14264/4ce35f0","url":null,"abstract":"This study aims to investigate the sound inducing fluid dynamic behaviour of a pipe section with a leak for two different leak configurations and the influence of fluid dynamic changes on acoustic emission (AE) signal features. It is found that turbulence and cavitation occur at the leak vicinity under high pressure. The intensity of these fluid dynamic changes is strongly related to the severity of the leakage. The AE responses to these occurrences are symptomatic to the leak severity. Interestingly, the cavitation is responsible for increasing AE RMS value, indicating severity of the damage.","PeriodicalId":369158,"journal":{"name":"Proceedings of the 22nd Australasian Fluid Mechanics Conference AFMC2020","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117134471","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Minghang Li, S. Karami, R. Sandberg, J. Soria, A. Ooi
{"title":"Heat Transfer Investigation on Under-expanded Supersonic Impinging Jets by Large Eddy Simulation","authors":"Minghang Li, S. Karami, R. Sandberg, J. Soria, A. Ooi","doi":"10.14264/618ac78","DOIUrl":"https://doi.org/10.14264/618ac78","url":null,"abstract":"","PeriodicalId":369158,"journal":{"name":"Proceedings of the 22nd Australasian Fluid Mechanics Conference AFMC2020","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124118332","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Investigation of vortical structures in the wake of pseudo-random roughness surfaces in hypersonic reacting boundary-layer flows","authors":"F. Ulrich, C. Stemmer","doi":"10.14264/3f17b5e","DOIUrl":"https://doi.org/10.14264/3f17b5e","url":null,"abstract":"","PeriodicalId":369158,"journal":{"name":"Proceedings of the 22nd Australasian Fluid Mechanics Conference AFMC2020","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128178072","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Khanarmuei, Neda Mardani, K. Suara, J. Sumihar, A. McCallum, R. Sidle, Richard J. Brown
A data assimilation (DA) framework assessed with an observing system simulation experiment (OSSE) can ensure reliable predictions for a water body, yet its application is very limited in shallow estuaries. In this study, we implemented an ensemble-based DA system to improve the accuracy of a hydrodynamic model of a micro-tidal estuary. Synthetic water level and velocity data were assimilated into the model in both single and dual variable DA forms. To evaluate the sensitivity of DA performance to the location of the hypothetical water level and velocity sensors, an OSSE assessment was used. Results revealed that DA performance is significantly sensitive to location of velocity observations, while relatively insensitive to location of water level observations. Our analysis suggests that the assimilation of velocity data at a location close to the downstream boundary (i.e., water level boundary) can result in a significant improvement in model estimates.
{"title":"Impact of sensor location on assimilated hydrodynamic model performance","authors":"M. Khanarmuei, Neda Mardani, K. Suara, J. Sumihar, A. McCallum, R. Sidle, Richard J. Brown","doi":"10.14264/739522a","DOIUrl":"https://doi.org/10.14264/739522a","url":null,"abstract":"A data assimilation (DA) framework assessed with an observing system simulation experiment (OSSE) can ensure reliable predictions for a water body, yet its application is very limited in shallow estuaries. In this study, we implemented an ensemble-based DA system to improve the accuracy of a hydrodynamic model of a micro-tidal estuary. Synthetic water level and velocity data were assimilated into the model in both single and dual variable DA forms. To evaluate the sensitivity of DA performance to the location of the hypothetical water level and velocity sensors, an OSSE assessment was used. Results revealed that DA performance is significantly sensitive to location of velocity observations, while relatively insensitive to location of water level observations. Our analysis suggests that the assimilation of velocity data at a location close to the downstream boundary (i.e., water level boundary) can result in a significant improvement in model estimates.","PeriodicalId":369158,"journal":{"name":"Proceedings of the 22nd Australasian Fluid Mechanics Conference AFMC2020","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134026593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiao-Peng Bi, Zhiwei Sun, T. Lau, Z. Alwahabi, G. Nathan
A laser-based technique is reported, employing simultaneous laser-induced fluorescence (LIF) and phosphorescence (LIP) to respectively mark the gas- and particle- phases and allow their simultaneous velocity measurement in a particle-laden flow. The technique discriminates the phases by optically separating the fluorescent and phosphorescent signals from each other and also from the scattering signals, thorough the novel use of optical filters and temporal separation. A proof-of-concept demonstration was conducted with using 250 μ m PMMA spherical particles and 4 μ m BAM:Eu 2+ phosphorescent tracers, suspended in a water cuvette. Under 355 nm excitation (3 rd harmonic of the Nd:YAG laser), both PMMA fluorescent and BAM:Eu 2+ phosphorescent signals are shown to be sufficiently strong for imaging with CCD cameras, and sufficiently separable with using spectral filters and temporal profiles.
本文报道了一种基于激光的技术，利用激光诱导荧光(LIF)和磷光(LIP)分别标记气相和颗粒相，并允许在颗粒负载流中同时测量它们的速度。该技术通过光学分离荧光和磷光信号以及散射信号来区分相位，通过光学滤光片和时间分离的新颖使用。使用250 μ m PMMA球形颗粒和4 μ m BAM:Eu 2+磷光示踪剂悬浮在水试管中，进行了概念验证演示。在355nm的激发下(Nd:YAG激光的三次谐波)，PMMA荧光和BAM:Eu 2+磷光信号都显示出足够强，可以用CCD相机成像，并且可以用光谱滤波器和时间剖面充分分离。
{"title":"Simultaneous planar measurements of gas and particle velocities in particle-laden flows: proof-of-concept","authors":"Xiao-Peng Bi, Zhiwei Sun, T. Lau, Z. Alwahabi, G. Nathan","doi":"10.14264/9eb1c68","DOIUrl":"https://doi.org/10.14264/9eb1c68","url":null,"abstract":"A laser-based technique is reported, employing simultaneous laser-induced fluorescence (LIF) and phosphorescence (LIP) to respectively mark the gas- and particle- phases and allow their simultaneous velocity measurement in a particle-laden flow. The technique discriminates the phases by optically separating the fluorescent and phosphorescent signals from each other and also from the scattering signals, thorough the novel use of optical filters and temporal separation. A proof-of-concept demonstration was conducted with using 250 μ m PMMA spherical particles and 4 μ m BAM:Eu 2+ phosphorescent tracers, suspended in a water cuvette. Under 355 nm excitation (3 rd harmonic of the Nd:YAG laser), both PMMA fluorescent and BAM:Eu 2+ phosphorescent signals are shown to be sufficiently strong for imaging with CCD cameras, and sufficiently separable with using spectral filters and temporal profiles.","PeriodicalId":369158,"journal":{"name":"Proceedings of the 22nd Australasian Fluid Mechanics Conference AFMC2020","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127850507","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Karandeniya, D. Holmes, E. Sauret, Yuantong T. Gu
Red blood cells (RBCs) are the main component of the blood and comprise about 45% of the total volume of blood. The key role of RBCs is to transfer oxygen from pulmonary capillaries to tissue capillaries, and transfer carbon dioxide from tissues to lungs. While some of these capillaries have uniform cross-sections, some non-uniform capillaries are also present. Often the diameters of these cross sections are smaller than the diameter of the RBCs. Yet because of the high deformability of its viscoelastic membrane, the RBCs are able to flow through these capillaries. The purpose of this analysis is therefore to investigate the flow activity of RBCs during their passage through a non-uniform capillary using the Lattice Boltzmann – Immersed Boundary (LB-IB) method.
{"title":"Numerical Study of the Flow Behaviour of Discocyte Red Blood Cell Through a Non-uniform Capillary","authors":"D. Karandeniya, D. Holmes, E. Sauret, Yuantong T. Gu","doi":"10.14264/99dec0a","DOIUrl":"https://doi.org/10.14264/99dec0a","url":null,"abstract":"Red blood cells (RBCs) are the main component of the blood and comprise about 45% of the total volume of blood. The key role of RBCs is to transfer oxygen from pulmonary capillaries to tissue capillaries, and transfer carbon dioxide from tissues to lungs. While some of these capillaries have uniform cross-sections, some non-uniform capillaries are also present. Often the diameters of these cross sections are smaller than the diameter of the RBCs. Yet because of the high deformability of its viscoelastic membrane, the RBCs are able to flow through these capillaries. The purpose of this analysis is therefore to investigate the flow activity of RBCs during their passage through a non-uniform capillary using the Lattice Boltzmann – Immersed Boundary (LB-IB) method.","PeriodicalId":369158,"journal":{"name":"Proceedings of the 22nd Australasian Fluid Mechanics Conference AFMC2020","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116338584","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A-priori evaluation of data-driven models for large-eddy simulations in natural convection","authors":"Liyuan Liu, C. Lav, Richard Sandberg","doi":"10.14264/397bc48","DOIUrl":"https://doi.org/10.14264/397bc48","url":null,"abstract":"","PeriodicalId":369158,"journal":{"name":"Proceedings of the 22nd Australasian Fluid Mechanics Conference AFMC2020","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123380972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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