In this study, a benchmark natural convection problem is studied under a Gay-Lussac type approximation incorporating centrifugal effects in the context of a new vorticity-stream-function approach. This approximation differs from the classic Boussinesq approximation in that density variations are considered in the advection term as well as the gravity term in the momentum equations. Such a treatment invokes Froude number as a non-Boussinesq parameter deviating results from the classic Boussinesq approximation. Numerical simulations of the natural convection in square cavity are performed up to ????=106 and ??=0.3 at ????=0.71 via proposed formulation and results are compared against the conventional Boussinesq approximation in terms of the average and local Nusselt number and entropy generation. Comparing results indicate that, up to ????=105, mentioned approaches are showing almost identical performance, but as the Rayleigh number exceeds 105, formed thermal boundary layer under Gay-Lussac type approximation is slightly thicker compared to the Boussinesq approximation accompanied by a stronger velocity gradient.
{"title":"Studying the natural convection problem in a square cavity by a new vorticity-stream-function approach","authors":"P. Mayeli, Tzekih Tsai, G. Sheard","doi":"10.14264/b2c1622","DOIUrl":"https://doi.org/10.14264/b2c1622","url":null,"abstract":"In this study, a benchmark natural convection problem is studied under a Gay-Lussac type approximation incorporating centrifugal effects in the context of a new vorticity-stream-function approach. This approximation differs from the classic Boussinesq approximation in that density variations are considered in the advection term as well as the gravity term in the momentum equations. Such a treatment invokes Froude number as a non-Boussinesq parameter deviating results from the classic Boussinesq approximation. Numerical simulations of the natural convection in square cavity are performed up to ????=106 and ??=0.3 at ????=0.71 via proposed formulation and results are compared against the conventional Boussinesq approximation in terms of the average and local Nusselt number and entropy generation. Comparing results indicate that, up to ????=105, mentioned approaches are showing almost identical performance, but as the Rayleigh number exceeds 105, formed thermal boundary layer under Gay-Lussac type approximation is slightly thicker compared to the Boussinesq approximation accompanied by a stronger velocity gradient.","PeriodicalId":369158,"journal":{"name":"Proceedings of the 22nd Australasian Fluid Mechanics Conference AFMC2020","volume":"97 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":"122406530","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}
Xinyu Liu, Aleš Srna, H. L. Yip, S. Kook, Qing Nian, E. Hawkes
Hydrogen direct injection (DI) in a dual-fuel diesel engine is a new technology that can resolve two major issues of its port injection counterpart – knocking and NOx emissions. Compared to widely studied hydrogen port injection in a diesel engine, the hydrogen DI concept executes a near topdead centre (TDC) injection to cause hydrogen mixingcontrolled combustion. The slower burning rate is expected to hinder a rapid pressure rise and subsequent pressure ringing (i.e. knocking) and to reduce NOx emissions, which are problematic in premixed combustion dominant, hydrogen port injection dual-fuel diesel engines. This study directly compares the in-cylinder pressure, efficiency and engine-out emissions of port injected and direct injected hydrogen-diesel dual-fuel combustion in the same engine. The tests were performed in a single-cylinder engine equipped with three injection systems including a hydrogen port injector, a hydrogen direct injector and a common-rail diesel direct injector. The engine was operated at intermediate load using a fixed total energy input of 820 J with hydrogen energy fraction of 50%. The results show that mixing-controlled combustion of the hydrogen in direct injection mode leads to lower in-cylinder pressure and thus lower engine efficiency. However, the severe pressure ringing observed for the hydrogen port injection is avoided and engine-out NOx emission is reduced, indicating the hydrogen DI operation is more stable, its combustion is cleaner and a higher hydrogen utilisation can be achieved.
{"title":"Comparison of hydrogen port injection and direct injection (DI) in a single-cylinder dual-fuel diesel engine","authors":"Xinyu Liu, Aleš Srna, H. L. Yip, S. Kook, Qing Nian, E. Hawkes","doi":"10.14264/a1cd1dc","DOIUrl":"https://doi.org/10.14264/a1cd1dc","url":null,"abstract":"Hydrogen direct injection (DI) in a dual-fuel diesel engine is a new technology that can resolve two major issues of its port injection counterpart – knocking and NOx emissions. Compared to widely studied hydrogen port injection in a diesel engine, the hydrogen DI concept executes a near topdead centre (TDC) injection to cause hydrogen mixingcontrolled combustion. The slower burning rate is expected to hinder a rapid pressure rise and subsequent pressure ringing (i.e. knocking) and to reduce NOx emissions, which are problematic in premixed combustion dominant, hydrogen port injection dual-fuel diesel engines. This study directly compares the in-cylinder pressure, efficiency and engine-out emissions of port injected and direct injected hydrogen-diesel dual-fuel combustion in the same engine. The tests were performed in a single-cylinder engine equipped with three injection systems including a hydrogen port injector, a hydrogen direct injector and a common-rail diesel direct injector. The engine was operated at intermediate load using a fixed total energy input of 820 J with hydrogen energy fraction of 50%. The results show that mixing-controlled combustion of the hydrogen in direct injection mode leads to lower in-cylinder pressure and thus lower engine efficiency. However, the severe pressure ringing observed for the hydrogen port injection is avoided and engine-out NOx emission is reduced, indicating the hydrogen DI operation is more stable, its combustion is cleaner and a higher hydrogen utilisation can be achieved.","PeriodicalId":369158,"journal":{"name":"Proceedings of the 22nd Australasian Fluid Mechanics Conference AFMC2020","volume":"4 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":"114425670","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}
Despite the Earth being composed of 70% water, only a minor fraction of 2.5% is fresh while the remaining is saline, thus being unconsumable. Among the fresh available, only 1% is readily accessible. To tackle this problem, desalination has been recognized as one of the most effective. However, the huge reliance on fossil fuels to operate the desalination plants is not sustainable economically on the long run. Thus, solar energy integrated desalination technologies will provide an alternative which is more sustainable. This project demonstrates the concept of an autonomous small-scale vacuum desalination system which is powered by a solar charged battery using low cost equipment. The system produces fresh consumable water by removing unwanted particles and soluble from the seawater through a process of heating the seawater to a low temperature of 55 ⁰ C. The heated water is then subjected to a low surrounding pressured of -95 kPa (gauge, at sea level) in a Vacuum Tank in which the water boils. The water vapour is then passed through a copper pipe that is exposed to the normal ambient temperature of about 25 ⁰ C, wherein it condenses back into fresh liquid water that flows into a second Tank. Thus desalination has taken place.
{"title":"Autonomous Solar-Powered Desalination of Seawater using Low Pressure and Temperature","authors":"Amit Thapa, Bisan Tamang, N. Ojha, B. P. Huynh","doi":"10.14264/0428dbc","DOIUrl":"https://doi.org/10.14264/0428dbc","url":null,"abstract":"Despite the Earth being composed of 70% water, only a minor fraction of 2.5% is fresh while the remaining is saline, thus being unconsumable. Among the fresh available, only 1% is readily accessible. To tackle this problem, desalination has been recognized as one of the most effective. However, the huge reliance on fossil fuels to operate the desalination plants is not sustainable economically on the long run. Thus, solar energy integrated desalination technologies will provide an alternative which is more sustainable. This project demonstrates the concept of an autonomous small-scale vacuum desalination system which is powered by a solar charged battery using low cost equipment. The system produces fresh consumable water by removing unwanted particles and soluble from the seawater through a process of heating the seawater to a low temperature of 55 ⁰ C. The heated water is then subjected to a low surrounding pressured of -95 kPa (gauge, at sea level) in a Vacuum Tank in which the water boils. The water vapour is then passed through a copper pipe that is exposed to the normal ambient temperature of about 25 ⁰ C, wherein it condenses back into fresh liquid water that flows into a second Tank. Thus desalination has taken place.","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":"131787540","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}
Flapping flight strategy is widely adopted by insects and birds, which has drawn considerable attentions due to its excellent aerodynamic performance. It is worth noting that the good performance and great agility is also achieved with low noise. To apply this flight strategy to engineering, it is necessary to conduct corresponding studies to understand both the aerodynamics and the associated acoustics of the flapping wing. In this paper, the sound generated by flexible flapping wings during hovering flight is numerically studied by using an immersed boundary method. A series of parameters including the wing shape, wing-to-fluid mass ratio and wing flexibility are systematically examined at a low Reynolds number. It is found that appropriate flexibilities of the wing enhance the aerodynamic performance and reduce the noise generation.
{"title":"Sound generation by three-dimensional flapping wings during hovering flight","authors":"Li Wang, F. Tian","doi":"10.14264/6ff6dca","DOIUrl":"https://doi.org/10.14264/6ff6dca","url":null,"abstract":"Flapping flight strategy is widely adopted by insects and birds, which has drawn considerable attentions due to its excellent aerodynamic performance. It is worth noting that the good performance and great agility is also achieved with low noise. To apply this flight strategy to engineering, it is necessary to conduct corresponding studies to understand both the aerodynamics and the associated acoustics of the flapping wing. In this paper, the sound generated by flexible flapping wings during hovering flight is numerically studied by using an immersed boundary method. A series of parameters including the wing shape, wing-to-fluid mass ratio and wing flexibility are systematically examined at a low Reynolds number. It is found that appropriate flexibilities of the wing enhance the aerodynamic performance and reduce the noise generation.","PeriodicalId":369158,"journal":{"name":"Proceedings of the 22nd Australasian Fluid Mechanics Conference AFMC2020","volume":"46 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":"124003406","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}
A. Cook, A. Babanin, D. Sgarioto, P. Graham, Jenny Mathew, A. Skvortsov, R. Manasseh, D. Tothova
{"title":"A UAV ‘mobile buoy’ for measuring surface waves","authors":"A. Cook, A. Babanin, D. Sgarioto, P. Graham, Jenny Mathew, A. Skvortsov, R. Manasseh, D. Tothova","doi":"10.14264/8e7141e","DOIUrl":"https://doi.org/10.14264/8e7141e","url":null,"abstract":"","PeriodicalId":369158,"journal":{"name":"Proceedings of the 22nd Australasian Fluid Mechanics Conference AFMC2020","volume":"9 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":"121155629","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}
Numerical simulations have been carried out to investigate the unsteady natural convection flow in a cavity subjected to a sidewall heat flux varying sinusoidally with time. With all walls non-slip and the upper and lower boundaries and one sidewall adiabatic, the heating and cooling on the other sidewall produces an alternating direction natural convection boundary layer that discharges hot fluid to the top and cold fluid to the bottom of the cavity, generating a strong and time-varying thermal stratification in the cavity interior. The thermal stratification is shown to be strongly dependent on the forcing frequency.
{"title":"Natural convection in a cavity with time-dependent flux boundary","authors":"L. Zhou, S. Armfield, Wenxian Lin","doi":"10.14264/e02d05f","DOIUrl":"https://doi.org/10.14264/e02d05f","url":null,"abstract":"Numerical simulations have been carried out to investigate the unsteady natural convection flow in a cavity subjected to a sidewall heat flux varying sinusoidally with time. With all walls non-slip and the upper and lower boundaries and one sidewall adiabatic, the heating and cooling on the other sidewall produces an alternating direction natural convection boundary layer that discharges hot fluid to the top and cold fluid to the bottom of the cavity, generating a strong and time-varying thermal stratification in the cavity interior. The thermal stratification is shown to be strongly dependent on the forcing frequency.","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":"126699906","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}
C. Rathnayaka, C. Karunasena, W. Senadeera, Yuantong T. Gu
Computational modelling of plant cellular materials and relevant mechanics are of interest in numerous research fields. Depending on the complex fluid and solid mechanics involved, there are many numerical modelling approaches applicable in the development of such computational models. This research investigation focuses on computational modelling threedimensional (3-D) microfluidics of parenchyma cells of three different plant cellular materials: apple, potato and grape with the intention of studying corresponding physical deformations under external mechanical compression which potentially can derive valuable insights about processing of such plant materials. A coupled Smoothed Particle Hydrodynamics (SPH) and Coarse-Grained (CG) approach has been utilised to numerically model the cell fluid and cell wall mechanics, respectively. Quantitative simulation results indicated almost similar cell deformations yielding to top and bottom flat surfaces. In terms of stress-strain behaviour, apple and grape cells revealed stiffer behaviour relative the potato cell. It is evident based on this study that depending on the differences of physical properties of plant cells, their behaviour under compression varies. Findings of this research can be potentially beneficial in further studies towards prediction of 3-D tissue deformation under external mechanical loading.
{"title":"Modelling 3-D cellular microfluidics of different plant cells for the prediction of cellular deformations under external mechanical compression: A SPH-CG-based computational study","authors":"C. Rathnayaka, C. Karunasena, W. Senadeera, Yuantong T. Gu","doi":"10.14264/1374f47","DOIUrl":"https://doi.org/10.14264/1374f47","url":null,"abstract":"Computational modelling of plant cellular materials and relevant mechanics are of interest in numerous research fields. Depending on the complex fluid and solid mechanics involved, there are many numerical modelling approaches applicable in the development of such computational models. This research investigation focuses on computational modelling threedimensional (3-D) microfluidics of parenchyma cells of three different plant cellular materials: apple, potato and grape with the intention of studying corresponding physical deformations under external mechanical compression which potentially can derive valuable insights about processing of such plant materials. A coupled Smoothed Particle Hydrodynamics (SPH) and Coarse-Grained (CG) approach has been utilised to numerically model the cell fluid and cell wall mechanics, respectively. Quantitative simulation results indicated almost similar cell deformations yielding to top and bottom flat surfaces. In terms of stress-strain behaviour, apple and grape cells revealed stiffer behaviour relative the potato cell. It is evident based on this study that depending on the differences of physical properties of plant cells, their behaviour under compression varies. Findings of this research can be potentially beneficial in further studies towards prediction of 3-D tissue deformation under external mechanical loading.","PeriodicalId":369158,"journal":{"name":"Proceedings of the 22nd Australasian Fluid Mechanics Conference AFMC2020","volume":"24 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":"121075269","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":"Modelling the third-order velocity structure function in the scaling range at finite Reynolds numbers","authors":"L. Djenidi, R. Antonia","doi":"10.14264/3c0765d","DOIUrl":"https://doi.org/10.14264/3c0765d","url":null,"abstract":"","PeriodicalId":369158,"journal":{"name":"Proceedings of the 22nd Australasian Fluid Mechanics Conference AFMC2020","volume":"20 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":"124970422","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}
G. M. Hasan Shahariar, T. Bodisco, T. C. Van, N. Surawski, M. Sajjad, A. Kabir, Z. Ristovski, Richard J. Brown
Light-duty diesel vehicles contribute significantly to urban air pollution. Laboratory-based standard driving test cycles do not take into account external driving factors, which greatly impact the vehicle emissions compared to the real-world driving emission (RDE) measurements. This results in higher emission levels obtained by RDE tests, compared to the standard approaches. In the current study, an RDE measurement campaign has been conducted in Brisbane city traffic using a portable emission measurement system (PEMS). Thirty drivers with a wide variety of driving experiences participated using a Hyundai iLoad van in a custom test route. RDEs and driving parameters were recorded during each trip. Principal component analysis (PCA) was applied to investigate the relationship between driving dynamics and vehicle emissions. Also, the impact of different trips, driving time, and driving experience on driving behaviour and emissions. Route familiarity, traffic density, and driving experience have a strong impact on driving behaviour and emissions. The driver's response to changing traffic, unknown routes, and vehicles significantly vary among different drivers which results in a high volume of transient events (frequent acceleration and deceleration). Transient events are very common in city driving which has a strong correlation to vehicle emissions.
{"title":"Optimisation of driving-parameters and emissions of a diesel-vehicle using principal component analysis (PCA)","authors":"G. M. Hasan Shahariar, T. Bodisco, T. C. Van, N. Surawski, M. Sajjad, A. Kabir, Z. Ristovski, Richard J. Brown","doi":"10.14264/eeccc3f","DOIUrl":"https://doi.org/10.14264/eeccc3f","url":null,"abstract":"Light-duty diesel vehicles contribute significantly to urban air pollution. Laboratory-based standard driving test cycles do not take into account external driving factors, which greatly impact the vehicle emissions compared to the real-world driving emission (RDE) measurements. This results in higher emission levels obtained by RDE tests, compared to the standard approaches. In the current study, an RDE measurement campaign has been conducted in Brisbane city traffic using a portable emission measurement system (PEMS). Thirty drivers with a wide variety of driving experiences participated using a Hyundai iLoad van in a custom test route. RDEs and driving parameters were recorded during each trip. Principal component analysis (PCA) was applied to investigate the relationship between driving dynamics and vehicle emissions. Also, the impact of different trips, driving time, and driving experience on driving behaviour and emissions. Route familiarity, traffic density, and driving experience have a strong impact on driving behaviour and emissions. The driver's response to changing traffic, unknown routes, and vehicles significantly vary among different drivers which results in a high volume of transient events (frequent acceleration and deceleration). Transient events are very common in city driving which has a strong correlation to vehicle emissions.","PeriodicalId":369158,"journal":{"name":"Proceedings of the 22nd Australasian Fluid Mechanics Conference AFMC2020","volume":"46 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":"121987908","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}
S. G. Mallinson, A. Aquino, G. McBain, G. Horrocks, T. Barber, Charitha de, G. Yeoh
{"title":"Three-dimensional numerical simulation of air-flow in inkjet print-zones","authors":"S. G. Mallinson, A. Aquino, G. McBain, G. Horrocks, T. Barber, Charitha de, G. Yeoh","doi":"10.14264/45fd9cf","DOIUrl":"https://doi.org/10.14264/45fd9cf","url":null,"abstract":"","PeriodicalId":369158,"journal":{"name":"Proceedings of the 22nd Australasian Fluid Mechanics Conference AFMC2020","volume":"130 ","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131693325","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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