ORCID Profile
0000-0002-8175-4781
Current Organisation
University of Sydney
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Interdisciplinary Engineering | Fluidization And Fluid Mechanics | Computational Heat Transfer | Heat And Mass Transfer Operations | Turbulent Flows | Computational Fluid Dynamics | Fluidisation and Fluid Mechanics | Turbulent Flows | Combustion And Fuel Engineering | Mechanical Engineering | Chemical Engineering Not Elsewhere Classified |
ANZSRC Socio-Economic Objective (SEO)
Physical sciences | Industrial Energy Conservation and Efficiency | Residential Energy Conservation and Efficiency | Land and water management | Expanding Knowledge in Engineering | Energy Conservation and Efficiency not elsewhere classified | Iron and steel (e.g. ingots, bars, rods, shapes and sections) | Climate Change Models | Industry | Other
Related Links
Publications
Effective emissions reduction of high-mileage fleets through a catalytic converter and oxygen sensor replacement program.
Publisher: Elsevier BV
Date: 12-2022
DOI: 10.1016/J.SCITOTENV.2022.158004
Abstract: High-mileage vehicles such as taxis make disproportionately large contributions to urban air pollution due to their accelerated engine deterioration rates and high operation intensities despite their small proportions of the total fleet. Controlling emissions from these high-mileage fleets is thus important for improving urban air quality. This study evaluates the effectiveness of a pilot repair program in reducing emissions from taxis in Hong Kong which account for about 2 % of the total licensed vehicles. The emission factors of a large s le of 684 in-service taxis (including 121 for an emission survey program and 563 for a pilot repair program) were measured on transient chassis dynamometers. The results showed that 63 % of the s led taxis failed the driving cycle test before the pilot repair program. Most of failed taxis were NO related and 91 % of failed taxis exceeded the emission limits of at least two regulated pollutants simultaneously. After the pilot repair program by replacing catalytic converters and oxygen sensors, the failure rate was significantly reduced to only 7 %. In addition, the fleet average NO, HC and CO emission factors were reduced by 85 %, 82 % and 56 %, respectively. In addition, on-road remote sensing measurements confirmed the real-world emission reductions from the taxis that participated in the pilot repair program. These findings led to the implementation of a large-scale replacement program for all taxis in Hong Kong during 2013-2014, which was estimated to have reduced the total HC, CO and NO emissions by about 420, 2570 and 1000 t per year, respectively (equivalent to 5-8 % emission reductions from the whole road transport sector). Therefore, reducing emissions from the small high-mileage fleets is a highly cost-effective measure to improve urban air quality.
Magnified heat transfer from curved surfaces: A scaling prediction
Publisher: AIP Publishing
Date: 02-2021
DOI: 10.1063/5.0039974
Abstract: We report the first definitive Nusselt number scale of thermal boundary layers from curved surfaces characterized by the proposed non-dimensional curvature parameter ξ = R0/(HRa−1/4), where R0 denotes the radius of a curved surface, H denotes the corresponding finite height, and Ra denotes the global Rayleigh number of a virtual reference thermal boundary layer on a vertical flat surface. The Nusselt number scale is given by Nu ∼ ξ−1/5Ra1/4 in which Nu ∼ Ra1/4 is the scale for the flat surface case, revealing that curved thermal boundary layers could present times-of-magnitude larger heat flux with the curvature parameter being ξ ≪ 1. The velocity and thickness scales are also given by Vs∼R02/5Ra3/5H7/5κ and ΔT∼R01/5H4/5Ra1/5.
Scaling of Natural Convection of an Inclined Flat Plate: Sudden Cooling Condition
Publisher: ASME International
Date: 11-01-2011
DOI: 10.1115/1.4002982
Abstract: The natural convection boundary layer adjacent to an inclined plate subject to sudden cooling boundary condition has been studied. It is found that the cold boundary layer adjacent to the plate is potentially unstable to Rayleigh–Bénard instability if the Rayleigh number exceeds a certain critical value. A scaling relation for the onset of instability of the boundary layer is achieved. The scaling relations have been developed by equating important terms of the governing equations based on the development of the boundary layer with time. The flow adjacent to the plate can be classified broadly into a conductive, a stable convective, or an unstable convective regime determined by the Rayleigh number. Proper scales have been established to quantify the flow properties in each of these flow regimes. An appropriate identification of the time when the instability may set in is discussed. A numerical verification of the time for the onset of instability is also presented in this study. Different flow regimes based on the stability of the boundary layer have been discussed with numerical results.
Natural Convection Induced by Diurnal Heating and Cooling in a Reservoir with Slowly Varying Topography
Publisher: Japan Society of Mechanical Engineers
Date: 2006
DOI: 10.1299/JSMEB.49.605
A coupled three‐dimensional hydrodynamic model for predicting hypolimnetic oxygenation and epilimnetic mixing in a shallow eutrophic reservoir
Publisher: American Geophysical Union (AGU)
Date: 2017
DOI: 10.1002/2016WR019279
Urban Heat Island and Its Interaction with Heatwaves: A Review of Studies on Mesoscale
Publisher: MDPI AG
Date: 30-09-2021
DOI: 10.3390/SU131910923
Abstract: With rapid urbanization, population growth and anthropogenic activities, an increasing number of major cities across the globe are facing severe urban heat islands (UHI). UHI can cause complex impacts on the urban environment and human health, and it may bring more severe effects under heatwave (HW) conditions. In this paper, a holistic review is conducted to articulate the findings of the synergies between UHI and HW and corresponding mitigation measures proposed by the research community. It is worth pointing out that most studies show that urban areas are more vulnerable than rural areas during HWs, but the opposite is also observed in some studies. Changes in urban energy budget and major drivers are discussed and compared to explain such discrepancies. Recent studies also indicate that increasing albedo, vegetation fraction and irrigation can lower the urban temperature during HWs. Research gaps in this topic necessitate more studies concerning vulnerable cities in developing countries. Moreover, multidisciplinary studies considering factors such as UHI, HW, human comfort, pollution dispersion and the efficacy of mitigation measures should be conducted to provide more accurate and explicit guidance to urban planners and policymakers.
Natural convection boundary-layer adjacent to an inclined flat plate subject to sudden and ramp heating
Publisher: Elsevier BV
Date: 09-2010
PIV measurements of the K-type transition in natural convection boundary layers
Publisher: Elsevier BV
Date: 2019
Thermal modelling and experimental validation of a semi-transparent water wall system for Sydney climate
Publisher: Elsevier BV
Date: 10-2016
Transition to a periodic flow induced by a thin fin on the sidewall of a differentially heated cavity
Publisher: Elsevier BV
Date: 2009
Prandtl number scaling of unsteady natural convection boundary layers forPr >
Publisher:
American Physical Society (APS)
Date:
24-06-2009
Publisher: American Physical Society (APS)
Date: 24-06-2009
Unsteady natural convection in a reservoir sidearm induced by time-varying isothermal surface heating
Publisher: Elsevier BV
Date: 09-2013
Effect of the fin length on natural convection flow transition in a cavity
Publisher: Elsevier BV
Date: 08-2013
A Numerical Study of Turbulent Mixed Convection in a Smooth Horizontal Pipe
Publisher: ASME International
Date: 11-08-2016
DOI: 10.1115/1.4031112
Abstract: This paper presents a numerical study aimed at identifying a suitable turbulence model to describe the fully developed turbulent mixed convention of air in smooth horizontal pipes. The flow characteristics considered here are relevant to those typically observed in ventilated hollow core slab (VHCS) applications and, because of this, the adopted geometry and boundary conditions are represented by the Reynolds number and Richardson number of about 23,000 and 1.04, respectively. Empirical expressions available in the literature are used as reference to evaluate the accuracy of different turbulence models in predicting the dimensionless velocity (u+) and temperature (T+) profiles as well as the Nusselt number (Nu). Among the turbulence models considered, the standard and realizable k-ε models provide the best overall predictions of u+, T+, and Nu in the fully developed flow, and the former is recommended for the modeling of VHCS systems as it gives slightly better estimates of the Nu values.
Pr < 1
Publisher: American Physical Society (APS)
Date: 26-08-2010
Three‐Dimensional Effects of Artificial Mixing in a Shallow Drinking‐Water Reservoir
Publisher: American Geophysical Union (AGU)
Date: 2018
DOI: 10.1002/2017WR021127
Unsteady near-shore natural convection induced by surface cooling
Publisher: Cambridge University Press (CUP)
Date: 04-12-2010
DOI: 10.1017/S0022112009991765
Abstract: Natural convection in calm near-shore waters induced by daytime heating or nighttime cooling plays a significant role in cross-shore exchanges with significant biological and environmental implications. Having previously reported an improved scaling analysis on the daytime radiation-induced natural convection, the authors present in this paper a detailed scaling analysis quantifying the flow properties at varying offshore distances induced by nighttime surface cooling. Two critical functions of offshore distance have been derived to identify the distinctness and the stability of the thermal boundary layer. Two flow scenarios are possible depending on the bottom slope. For the relatively large slope scenario, three flow regimes are possible, which are discussed in detail. For each flow regime, all the possible distinctive subregions are identified. Two different sets of scaling incorporating the offshore-distance dependency have been derived for the conduction-dominated region and stable-convection-dominated region respectively. It is found that the scaling for flow in the stable-convection-dominated region also applies to the time-averaged mean flow in the unstable region. The present scaling results are verified by numerical simulations.
An experimental study of the unsteady thermal flow around a thin fin on a sidewall of a differentially heated cavity
Publisher: Elsevier BV
Date: 08-2008
Natural convection in a reservoir induced by sinusoidally varying temperature at the water surface
Publisher: Elsevier BV
Date: 05-2019
Natural transition in natural convection boundary layers
Publisher: Elsevier BV
Date: 08-2016
A CFD based approach for determining the optimum inclination angle of a roof-top solar chimney for building ventilation
Publisher: Elsevier BV
Date: 03-2020
A direct stability analysis of a radiation-induced natural convection boundary layer in a shallow wedge
Publisher: Cambridge University Press (CUP)
Date: 10-04-2003
Convection and instability of thermocapillary flow in a liquid bridge subject to a non-uniform rotating magnetic field
Publisher: Elsevier BV
Date: 10-2017
An experimental study of unsteady natural convection in a reservoir model cooled from the water surface
Publisher: Elsevier BV
Date: 2008
Effects of a transverse, horizontal magnetic field on natural convection of a paramagnetic fluid in a cube
Publisher: Elsevier BV
Date: 2009
A particle image velocimetry measurement of flow over a highly confined circular cylinder at 60% blockage ratio
Publisher: AIP Publishing
Date: 10-2021
DOI: 10.1063/5.0066606
Abstract: In this study, a Particle Image Velocimetry (PIV) measurement is carried out to investigate the flow past a highly confined circular cylinder at a fixed blockage ratio of 60%. The Reynolds number (Re) in terms of the cylinder diameter and the mean incoming flow velocity is varied from 318 to 1431. It is observed that the characteristic frequency of the separated shear layers is lified through a so-called frequency-filtering process. The instability of the separated shear layers causes two different vortex shedding modes including alternating and symmetric shedding modes, which are observed at Re = 927–1242. An intermittent switch between the two shedding modes is also observed. The theory of mixing layers is applied with modification to predict the characteristics of the separated shear layers, and the prediction shows a good agreement with the experimental data. It is found that the vortex roll-up and merging locations can be estimated by calculating the energy contents of in idual frequency modes.
On the stability of internally heated natural convection due to the absorption of radiation in a laterally confined fluid layer with a horizontal throughflow
Publisher: Elsevier BV
Date: 02-2015
Resonance of the thermal boundary layer adjacent to an isothermally heated vertical surface
Publisher: Cambridge University Press (CUP)
Date: 29-04-2013
DOI: 10.1017/JFM.2013.167
Abstract: The instability characteristics and resonance of a natural convection boundary layer adjacent to an isothermally heated vertical surface are investigated using direct stability analyses. The detailed streamwise evolution of the boundary-layer frequencies is visualized via the power spectra of the temperature time series in the thermal boundary layer. It is found that the entire thermal boundary layer may be ided into three distinct regions according to the frequency profile, which include an upstream low-frequency region, a transitional region (with both low- and high-frequency bands) and a downstream high-frequency region. The high-frequency band in the downstream region determines the resonance characteristics of the thermal boundary layer, which can be triggered by a single-mode perturbation at frequencies within the high-frequency band. The single-mode perturbation experiments further reveal that the maximum resonance of the thermal boundary layer is triggered by a perturbation at the characteristic frequency of the boundary layer. For the boundary-layer flow at $\\mathit{Ra}= 3. 6\\times 1{0}^{10} $ and $\\mathit{Pr}= 7$ , a net heat transfer enhancement of up to 44 % is achieved by triggering resonance of the boundary layer. This significant enhancement of heat transfer is due to the resonance-induced advancement of the laminar–turbulent transition, which is found to be dependent on the perturbation frequency and litude. Evidence from different perspectives revealing the same position of the transition are provided and discussed. The outcomes of this investigation demonstrate the prospect of a resonance-based approach for enhancing heat transfer.
An experimental study of unsteady natural convection in a reservoir model subject to periodic thermal forcing using combined PIV and PIT techniques
Publisher: Springer Science and Business Media LLC
Date: 18-03-2009
Natural convection in attics subject to instantaneous and ramp cooling boundary conditions
Publisher: Elsevier BV
Date: 08-2010
Natural convection over vertical and horizontal heated flat surfaces: A review of recent progress focusing on underpinnings and implications for heat transfer and environmental applications
Publisher: AIP Publishing
Date: 10-2021
DOI: 10.1063/5.0065125
Abstract: Natural convection arising over vertical and horizontal heated flat surfaces is one of the most ubiquitous flows at a range of spatiotemporal scales. Despite significant developments over more than a century contributing to our fundamental understanding of heat transfer in natural convection boundary layers, certain “hidden” characteristics of these flows have received far less attention. Here, we review scattered progress on less visited fundamental topics that have strong implications to heat and mass transfer control. These topics include the instability characteristics, laminar-to-turbulent transition, and spatial flow structures of vertical natural convection boundary layers and large-scale plumes, dome, and circulating flows over discretely and entirely heated horizontal surfaces. Based on the summarized advancements in fundamental research, we elaborate on the selection of perturbations and provide an outlook on the development of perturbation generators and methods of altering large-scale flow structures as a potential means for heat and mass transfer control where natural convection is dominant.
A numerical investigation of conjugate thermal boundary layers in a differentially heated partitioned cavity filled with different fluids
Publisher: AIP Publishing
Date: 07-2020
DOI: 10.1063/5.0013600
Abstract: In this study, the instability mechanisms in the conjugate thermal boundary layers (TBLs) adjacent to a partition in a differentially heated dual-chamber cavity are investigated numerically. The two chambers of the cavity are filled with air (Pr = 0.71) and water (Pr = 8.58), and the partition is assumed to have a zero thickness. The effects of the aspect ratios of both chambers (Aair and Awater) and the overall temperature difference (ΔT) on the interactions between the conjugate air- and water-side TBLs are extensively investigated. It is found that Aair has a more significant impact on the instabilities of the TBLs than Awater. For a relatively small Aair (e.g., 10/3) and a relatively large Aair (e.g., 10), the water-side TBL resonates with the air-side TBL at the frequencies of the corner flow instabilities in the air chamber. For medium Aair (e.g., 4, 5, and 20/3), the air-side TBL becomes weakly turbulent, causing the water-side TBL to become chaotic. Furthermore, if ΔT is reduced, the air-side TBL becomes quasi-periodic, limiting the turbulence growth on the water side. A stability map illustrating the major instability mechanisms controlling the interactions between the conjugate TBLs is presented on the (Aair, Ra) domain for Awater = 5.
A numerical investigation of combined solar chimney and water wall for building ventilation and thermal comfort
Publisher: Elsevier BV
Date: 03-2020
Temperature oscillations in a differentially heated cavity with and without a fin on the sidewall
Publisher: Elsevier BV
Date: 04-2010
Effectiveness of a bubble-plume mixing system for managing phytoplankton in lakes and reservoirs
Publisher: Elsevier BV
Date: 04-2018
Statistical evaluation of on-road vehicle emissions measurement using a dual remote sensing technique.
Publisher: Elsevier BV
Date: 12-2020
Experimental observations of the thermal flow around a square obstruction on a vertical wall in a differentially heated cavity
Publisher: Springer Science and Business Media LLC
Date: 18-11-2005
CFD simulation of the drag effect of urban trees: Source term modification method revisited at the tree scale
Publisher: Elsevier BV
Date: 05-2020
Unsteady natural convection in a triangular enclosure induced by surface cooling
Publisher: Elsevier BV
Date: 04-2005
Experimental observation of surface morphology effect on crystallization fouling in plate heat exchangers
Publisher: Elsevier BV
Date: 2011
Natural convection induced by radiation in a water filled square cavity: Experimental observations
Publisher: Elsevier BV
Date: 2017
A numerical investigation of buoyancy induced turbulent air flow in an inclined passive wall solar chimney for natural ventilation
Publisher: Elsevier BV
Date: 04-2015
Natural convection induced by absorption of solar radiation in the near shore region of lakes and reservoirs: Experimental results
Publisher: Elsevier BV
Date: 2018
Convective heat loss from computational thermal manikin subject to outdoor wind environments
Publisher: Elsevier BV
Date: 2021
Numerical Simulation and Stability Study of Natural Convection in an Inclined Rectangular Cavity
Publisher: Hindawi Limited
Date: 2013
DOI: 10.1155/2013/198695
Abstract: This paper examines the process of instability of natural convection in an inclined cavity based on numerical simulations. The energy gradient method is employed to analyze the physics of the flow instability in natural convection. It is found that the maximum value of the energy gradient function in the flow field correlates well with the location where flow instability occurs. Meanwhile, the effects of the flow time, the plate length, and the inclination angle on the instability have also been discussed. It is observed that the locations of instabilities migrate right as the flow time increased. With the increase of plate length, the onset time of the instability on the top wall of the cavity decreases gradually and the locations of instabilities move to the right side. Furthermore, the locations of instability move left with the increase of the inclination angle in a certain range. However, these positions move right as the accumulation of the heat flux is restrained in the lower left corner of the cavity once the inclination angle exceeds a certain range.
Heat transfer through coupled thermal boundary layers induced by a suddenly generated temperature difference
Publisher: Elsevier BV
Date: 10-2009
Direct numerical simulation of the fully developed turbulent free convection flow in an asymmetrically heated vertical channel
Publisher: Elsevier BV
Date: 09-2023
Numerical Modeling of a Concurrent PIT/PIV Experiment with TLC Particles in a Reservoir Model Subject to Periodic Thermal Forcing
Publisher: Informa UK Limited
Date: 03-04-2014
Spanwise length effects on three-dimensional modelling of flow over a circular cylinder
Publisher: Elsevier BV
Date: 02-2001
A direct three-dimensional simulation of radiation-induced natural convection in a shallow wedge
Publisher: Elsevier BV
Date: 03-2003
Unsteady natural convection in a triangular enclosure induced by absorption of radiation
Publisher: Cambridge University Press (CUP)
Date: 10-06-2002
DOI: 10.1017/S0022112002008091
Abstract: The authors have previously reported a model experiment on the unsteady natural convection in a triangular domain induced by the absorption of solar radiation. This issue is reconsidered here both analytically and numerically. The present study consists of two parts: a scaling analysis and a numerical simulation. The scaling analysis for small bottom slopes reveals that a number of flow regimes are possible depending on the Rayleigh number and the relative value of certain non-dimensional parameters describing the flow. In a typical situation, the flow can be classified broadly into a conductive, a transitional or a convective regime determined merely by the Rayleigh number. Proper scales have been established to quantify the flow properties in each of these flow regimes. The numerical simulation has verified the scaling results.
Characteristics of instability of radiation-induced natural convection in shallow littoral waters
Publisher: Elsevier BV
Date: 2010
Modified smoothed particle hydrodynamics approach for modelling dynamic contact angle hysteresis
Publisher: Springer Science and Business Media LLC
Date: 22-02-2019
Vortex shedding suppression for flow over a circular cylinder near a plane boundary
Publisher: Elsevier BV
Date: 10-2000
Plume separation from an adiabatic horizontal thin fin placed at different heights on the sidewall of a differentially heated cavity
Publisher: Elsevier BV
Date: 02-2015
Flow reversal effects on buoyancy induced air flow in a solar chimney
Publisher: Elsevier BV
Date: 09-2012
Natural convection in attic-shaped spaces subject to sudden and ramp heating boundary conditions
Publisher: Springer Science and Business Media LLC
Date: 13-05-2010
Unsteady nearshore natural convection induced by constant isothermal surface heating
Publisher: Cambridge University Press (CUP)
Date: 20-07-2012
DOI: 10.1017/JFM.2012.283
Abstract: The present investigation is concerned with natural convection in a wedge-shaped domain induced by constant isothermal heating at the water surface. Complementary to the study of daytime heating by solar radiation relevant to nearshore regions of lakes and reservoirs previously reported by the same authors, this study focuses on sensible heating imposed by the atmosphere when it is warmer than the water body. A semi-analytical approach coupled with scaling analysis and numerical simulation is adopted to resolve the problem. Two flow regimes are identified depending on the comparison between the Rayleigh number and the inverse of the square of the bottom slope. For the lower Rayleigh number regime, the entire flow domain eventually becomes isothermal and stationary. For the higher Rayleigh number regime, the flow domain is composed of two distinct subregions, a conductive subregion near the shore and a convective subregion offshore. Within the conductive subregion, the maximum local flow velocity occurs when the thermal boundary layer reaches the local bottom, and the subregion eventually becomes isothermal and stationary. In the offshore convective subregion, a steady state is reached with a distinct thermal boundary layer below the surface and a steady flow velocity. The iding position between the two subregions and the major time and velocity scales governing the flow development in both subregions are proposed by the scaling analysis and validated by corresponding numerical simulation.
Suppressing Rayleigh-Benard convection in a cube using a strong magnetic field - Experimental heat transfer rate measurements and flow visualization
Publisher: Elsevier BV
Date: 02-2009
NATURAL CONVECTION IN A RESERVOIR SIDEARM SUBJECT TO SOLAR RADIATION: A TWO-DIMENSIONAL SIMULATION
Publisher: Informa UK Limited
Date: 07-2002
A numerical study on the thermal performance of night ventilated hollow core slabs cast with micro-encapsulated PCM concrete
Publisher: Elsevier BV
Date: 09-2016
Scaling and direct stability analyses of natural convection induced by absorption of solar radiation in a parallelepiped cavity
Publisher: Elsevier BV
Date: 02-2015
Influence of a horizontal magnetic field on the natural convection of paramagnetic fluid in a cube heated and cooled from two vertical side walls
Publisher: Elsevier BV
Date: 06-2008
A large eddy simulation of flow over a circular cylinder with circumferential triangular riblets: Effects of spanwise coverage ratio
Publisher: Elsevier BV
Date: 11-2022
A review of research and development on water wall for building applications
Publisher: Elsevier BV
Date: 2016
Natural convection in a reservoir sidearm subject to solar radiation: experimental observations
Publisher: Springer Science and Business Media LLC
Date: 05-2002
CFD simulation of the thermal performance of an opaque water wall system for Australian climate
Publisher: Elsevier BV
Date: 08-2016
A PIV measurement of the natural transition of a natural convection boundary layer
Publisher: Springer Science and Business Media LLC
Date: 2015
Solar chimney—A passive strategy for natural ventilation
Publisher: Elsevier BV
Date: 08-2011
Hydrodynamic characteristics of a confined circular cylinder in cross-flows
Publisher: Elsevier BV
Date: 02-2021
An experimental study of the coupled thermal boundary layers adjacent to a partition in a differentially heated cavity
Publisher: Elsevier BV
Date: 04-2014
Shadowgraph observations of the transition of the thermal boundary layer in a side-heated cavity
Publisher: Springer Science and Business Media LLC
Date: 20-04-2005
Natural convection in a differentially heated cavity with two horizontal adiabatic fins on the sidewalls
Publisher: Elsevier BV
Date: 05-2014
A numerical study of drag reduction performance of simplified shell surface microstructures
Publisher: Elsevier BV
Date: 12-2020
Transient natural convection flows around a thin fin on the sidewall of a differentially heated cavity
Publisher: Cambridge University Press (CUP)
Date: 07-10-2009
DOI: 10.1017/S0022112009990991
Abstract: Transient natural convection flows around a thin fin on the sidewall of a differentially heated cavity, which includes a lower intrusion under the fin, a starting plume bypassing the fin and a thermal flow entrained into the vertical thermal boundary layer downstream of the fin in a typical case, are investigated using a scaling analysis and direct numerical simulations. The obtained scaling relations show that the thickness and velocity of the transient natural convection flows around the fin are determined by different dynamic and energy balances, which can be either a buoyancy-viscous balance or a buoyancy-inertial balance, depending on the Rayleigh number, the Prandtl number and the fin length. A time scale of the transition from a buoyancy-viscous flow regime to a buoyancy-inertial flow regime is obtained. The major scaling relations quantifying the transient natural convection flows are also validated by direct numerical simulations. In general, there is a good agreement between the scaling predictions and the corresponding numerical results.
A scaling investigation of the laminar convective flow in a solar chimney for natural ventilation
Publisher: Elsevier BV
Date: 02-2014
On numerical modelling of conjugate turbulent natural convection and radiation in a differentially heated cavity
Publisher: Elsevier BV
Date: 12-2015
A review of strategies for mitigating roadside air pollution in urban street canyons
Publisher: Elsevier BV
Date: 07-2021
Effects of adiabatic extensions on heat transfer through a differentially heated square cavity
Publisher: Elsevier BV
Date: 11-2010
Mixing in internally heated natural convection flow and scaling for a quasi-steady boundary layer
Publisher: Cambridge University Press (CUP)
Date: 17-12-2014
DOI: 10.1017/JFM.2014.680
Abstract: This study considers the natural convection flow in a water body subjected to heating by solar radiation. The investigation into this type of natural convection flow has been motivated by the fact that it is known to play a crucial role in the daytime heat and mass transfer in shallow regions of natural water reservoirs and lakes, with a resultant impact on biological activity. An analytical solution for temperature in such an internally heated system shows that the temperature stratification consists of an upper stable stratification and a lower unstable stratification. One of the important consequences of such a nonlinear temperature stratification is the limitation of the mixing driven by rising thermal plumes with the penetration length scale of the plumes determining the lower mixed layer thickness. A theoretical analysis conducted in the present study suggests that in relatively deep waters, the lower mixed layer thickness is equal to the attenuation length of the radiation, which has important implications for water quality, including the transport of pollutants and nutrients in the water body. Scalings are also obtained for the quasi-steady boundary layer. The theoretical analysis is validated against numerical simulations.
Enhancing heat transfer using flow-induced oscillations of a flexible baffle attached to a vertical heated flat surface
Publisher: Elsevier BV
Date: 12-2023
OBSERVATION AND SIMULATION OF THE DOUBLE LAYER STRUCTURE OF THE THERMAL BOUNDARY LAYER IN A SIDE-HEATED CAVITY
Publisher: Begell House
Date: 2006
Transport of pollutant particles in a reservoir due to diurnal temperature variation
Publisher: Elsevier BV
Date: 04-2014
Enhancing natural convection in a cube using a strong magnetic field - Experimental heat transfer rate measurements and flow visualization
Publisher: Elsevier BV
Date: 10-2009
On the stability of transient penetrative convection driven by internal heating coupled with a thermal boundary condition
Publisher: Elsevier BV
Date: 05-2015
Field measurement of the urban pedestrian level wind turbulence
Publisher: Elsevier BV
Date: 05-2021
Transition of natural convection boundary layers-a revisit by Bicoherence analysis
Publisher: Elsevier BV
Date: 11-2014
Various aspects of camera settings and image processing in the calibration of thermo-chromic liquid crystals for accurate particle image thermometry measurements
Publisher: Springer Science and Business Media LLC
Date: 30-04-2010
Transient Behaviour of Natural Convection in a Reservoir Model Induced by Surface Heating
Publisher: Japan Society of Mechanical Engineers
Date: 2012
DOI: 10.1299/JTST.7.211
A state-of-the-art review of flows past confined circular cylinders
Publisher: AIP Publishing
Date: 07-2023
DOI: 10.1063/5.0157470
Abstract: In this paper, we have reviewed the state-of-the-art of research on flow past a circular cylinder symmetrically placed between two parallel plates separated by a finite distance. Such flow, referred to as a confined flow or flow past a confined cylinder in this study, is characterized by the blockage ratio—the ratio of the cylinder diameter to the distance between the plates. Confined flows are common in engineering systems, but the interest in studying flows over confined cylinders was motivated by the need to correct unavoidable blockage effects in physical experiments for unconfined cylinders. A very early work on this topic was published in 1944. Since then, interest has gradually expanded to understanding the wake dynamics and hydrodynamic properties of confined cylinders at different blockage ratios. The emergence and further developments of the Computational Fluid Dynamics and Particle Image Velocimetry techniques have enabled researchers to unveil important and complex features of confined flows, such as the two-dimensional to three-dimensional flow transition, the analogy of the separated shear layers to mixing layers, different vortex shedding modes, and the asymmetry of confined flows at high blockage ratios. To date, there has been no systematic review dedicated to confined flows. The present review fills the gap and is aimed to provide a comprehensive account of relevant studies including a historical perspective of the studies, significant research findings, and most recent advancement of the knowledge. Further, we have also identified a number of research gaps for further investigations.
An experimental investigation of an inclined passive wall solar chimney for natural ventilation
Publisher: Elsevier BV
Date: 09-2014
Unsteady natural convection induced by diurnal temperature changes in a reservoir with slowly varying bottom topography
Publisher: Elsevier BV
Date: 10-2009
A finite difference solution of the shear flow over a circular cylinder
Publisher: Elsevier BV
Date: 03-2000
Unsteady flow and heat transfer adjacent to the sidewall wall of a differentially heated cavity with a conducting and an adiabatic fin
Publisher: Elsevier BV
Date: 06-2011
The K-type and H-type transitions of natural convection boundary layers
Publisher: Cambridge University Press (CUP)
Date: 05-07-2017
DOI: 10.1017/JFM.2017.354
Abstract: The K-type and H-type transitions of a natural convection boundary layer of a fluid of Prandtl number 7 adjacent to an isothermally heated vertical surface are investigated by means of three-dimensional direct numerical simulation (DNS). These two types of transitions refer to different flow features at the transitional stage from laminar to turbulence caused by two different types of perturbations. To excite the K-type transition, superimposed Tollmien–Schlichting (TS) and oblique waves of the same frequency are introduced into the boundary layer. It is found that a three-layer longitudinal vortex structure is present in the boundary layer undergoing the K-type transition. The typical aligned $\\wedge$ -shaped vortices characterizing the K-type transition are observed for the first time in pure natural convection boundary layers. For exciting the H-type transition, superimposed TS and oblique waves of different frequencies, with the frequency of the oblique waves being half of the frequency of the TS waves, are introduced into the boundary layer. Unlike the three-layer longitudinal vortex structure observed in the K-type transition, a double-layer longitudinal vortex structure is observed in the boundary layer undergoing the H-type transition. The successively staggered $\\wedge$ -shaped vortices characterizing the H-type transition are also observed in the downstream boundary layer. The staggered pattern of $\\wedge$ -shaped vortices is considered to be caused by temporal modulation of the TS and oblique waves. Interestingly the flow structures of both the K-type and H-type transitions observed in the natural convection boundary layer are qualitatively similar to those observed in Blasius boundary layers. However, an analysis of turbulence energy production suggests that the turbulence energy production by buoyancy rather than Reynolds stresses dominates the K-type and H-type transitions. In contrast, the turbulence energy production by Reynolds stresses is the only factor contributing to the transition in Blasius boundary layers.
Scaling of natural convection of an inclined flat plate: Ramp cooling condition
Publisher: Elsevier BV
Date: 11-2010
Corrigendum to “CFD simulation of the thermal performance of an opaque water wall system for Australian climate” [Solar Energy 133 (2016) 141–154]
Publisher: Elsevier BV
Date: 10-2016
Re-examination of the effect of a plane boundary on force and vortex shedding of a circular cylinder
Publisher: Elsevier BV
Date: 04-1999
Unsteady natural convection in a water-filled isosceles triangular enclosure heated from below
Publisher: Elsevier BV
Date: 06-2008
Characterization of linear and oscillatory behaviours of radiation-induced natural convection boundary layer in response to constant and time-varying thermal forcing
Publisher: Elsevier BV
Date: 08-2015
Theoretical modeling of combined solar chimney and water wall for buildings
Publisher: Elsevier BV
Date: 03-2019
A numerical study of unsteady natural convection induced by iso-flux surface cooling in a reservoir model
Publisher: Elsevier BV
Date: 2009
Unsteady natural convection in a triangular enclosure induced by absorption of radiation - A revisit by improved scaling analysis
Publisher: Cambridge University Press (CUP)
Date: 10-03-2009
DOI: 10.1017/S0022112008005077
Abstract: The present study is concerned with radiation-induced natural convection in a water-filled triangular enclosure with a sloping bottom, which is directly relevant to buoyancy-driven flows in littoral regions. An improved scaling analysis is carried out to reveal more detailed features of the flow than a previously reported analysis. Two critical functions of the Rayleigh number with respect to the horizontal position are derived from the scaling for identifying the distinctness and stability of the thermal boundary layer. Four flow scenarios are possible, depending on the bottom slope and the maximum water depth. For each flow scenario, the flow domain may be composed of multiple subregions with distinct thermal and flow features, depending on the Rayleigh number. The iding points between neighbouring subregions are determined by comparisons of the critical functions of the Rayleigh number with the global Rayleigh number. Position-dependent scales have been established to quantify the flow properties in different subregions. The different flow regimes for the case with relatively large bottom slopes and shallow waters are examined in detail. The present scaling results are verified by numerical simulations.
Resonance in the flow past a highly confined circular cylinder
Publisher: AIP Publishing
Date: 08-2022
DOI: 10.1063/5.0099948
Abstract: A three-dimensional direct numerical simulation is carried out to investigate the response of the flow past a highly confined circular cylinder to single-mode sinusoidal perturbations. The Reynolds number is fixed at 1000, and the blockage ratio (the ratio of the cylinder diameter to the distance between two lateral walls) is fixed at 0.6. Local perturbations are introduced upstream of the cylinder at normalized excitation frequencies (fe/f0) from 0.2 to 3.4, where f0 is the vortex shedding frequency in an unperturbed flow. It is observed that the vortex shedding frequency of the perturbed flows (fs) and the excitation frequency (fe) are locked-on in four distinct modes including fs = 2.0fe, fs = 1.5fe, fs = 1.0fe, and fs = 0.5fe, respectively. Among them, the fundamental lock-on with fs = 0.5fe appears over a wide range of excitation frequencies (fe/f0 = 1.4–2.8). By contrast, only the fundamental lock-on regime of fs = 0.5fe is observed when perturbing an unconfined flow at the same Reynolds number, highlighting the significant impact of confinement on the lock-on behavior. It is further revealed that the lock-on behavior is controlled by the responses of separated shear layers in the near wake, which switch from higher modes to lower modes with increasing excitation frequency in the confined flow.
On the double-layer structure of the boundary layer adjacent to a sidewall of a differentially heated cavity
Publisher: Elsevier BV
Date: 07-2008
Improved Modeling of Sediment Oxygen Kinetics and Fluxes in Lakes and Reservoirs
Publisher: American Chemical Society (ACS)
Date: 23-01-2020
Abstract: To understand water quality degradation during hypoxia, we need to understand sediment oxygen fluxes, the main oxygen sink in shallow hypolimnia. Kinetic models, which integrate diffusion and consumption of dissolved oxygen (DO) in sediments, usually assume a downward flux of DO from the sediment-water interface (SWI) with a zero-flux condition at the lower boundary of the oxic sediment layer. In this paper, we separately account for the oxidation of an upward flux of reduced compounds by introducing a negative flux of DO as a lower boundary condition. Using in situ measurements in two lakes, kinetic models were fit to DO microprofiles using zero-order and first-order kinetics with both zero and non-zero lower boundary conditions. Based on visual inspection and goodness-of-fit criteria, the negative-flux lower boundary condition, -0.25 g O
A numerical simulation of transient near-shore natural convection induced by ramped iso-flux cooling
Publisher: Elsevier BV
Date: 12-2012
Scaling for unsteady thermo-magnetic convection boundary layer of paramagnetic fluids of Pr > 1 in micro-gravity conditions
Publisher: Elsevier BV
Date: 12-2009
Scaling of unsteady natural convection boundary layers with a non-instantaneous initiation
Publisher: Elsevier BV
Date: 10-2009
Natural convection and heat transfer in attics subject to periodic thermal forcing
Publisher: Elsevier BV
Date: 10-2010
Relative Performance of 1-D Versus 3-D Hydrodynamic, Water-Quality Models for Predicting Water Temperature and Oxygen in a Shallow, Eutrophic, Managed Reservoir
Publisher: MDPI AG
Date: 03-01-2021
DOI: 10.3390/W13010088
Abstract: Many researchers use one-dimensional (1-D) and three-dimensional (3-D) coupled hydrodynamic and water-quality models to simulate water quality dynamics, but direct comparison of their relative performance is rare. Such comparisons may quantify their relative advantages, which can inform best practices. In this study, we compare two 1-year simulations in a shallow, eutrophic, managed reservoir using a community-developed 1-D model and a 3-D model coupled with the same water-quality model library based on multiple evaluation criteria. In addition, a verified bubble plume model is coupled with the 1-D and 3-D models to simulate the water temperature in four epilimnion mixing periods to further quantify the relative performance of the 1-D and 3-D models. Based on the present investigation, adopting a 1-D water-quality model to calibrate a 3-D model is time-efficient and can produce reasonable results 3-D models are recommended for simulating thermal stratification and management interventions, whereas 1-D models may be more appropriate for simpler model setups, especially if field data needed for 3-D modeling are lacking.
Study of unsteady natural convection induced by absorption of radiation based on a three-waveband attenuation model
Publisher: IOP Publishing
Date: 22-08-2014
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