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Similarity solutions for the stagnation-point flow and heat transfer over a nonlinearly stretching/shrinking sheet

Norfifah Bachok, Anuar Ishak

Sains Malaysiana, 2011;40:1297-1300.

This paper presents a numerical analysis of a stagnation-point flow towards a nonlinearly stretching/shrinking sheet immersed in a viscous fluid. The stretching/shrinking velocity and the external flow velocity impinges normal to the stretching/shrinking sheet are assumed to be in the form U ~ xm, where m is a constant and x is the distance from the stagnation point. The governing partial differential equations are converted into ordinary ones by a similarity transformation, before being solved numerically. The variations of the skin friction coefficient and the heat transfer rate at the surface with the governing parameters are graphed and tabulated. Different from a stretching sheet, it is found that the solutions for a shrinking sheet are non-unique for m > 1/3.

Matched MeSH terms: Hydrodynamics
Fulltext Optimization of a continuous hybrid impeller mixer via computational fluid dynamics

Othman N, Kamarudin SK, Takriff MS, Rosli MI, Engku Chik EM, Meor Adnan MA

ScientificWorldJournal, 2014;2014:619474.
PMID: 25170524 DOI: 10.1155/2014/619474

This paper presents the preliminary steps required for conducting experiments to obtain the optimal operating conditions of a hybrid impeller mixer and to determine the residence time distribution (RTD) using computational fluid dynamics (CFD). In this paper, impeller speed and clearance parameters are examined. The hybrid impeller mixer consists of a single Rushton turbine mounted above a single pitched blade turbine (PBT). Four impeller speeds, 50, 100, 150, and 200 rpm, and four impeller clearances, 25, 50, 75, and 100 mm, were the operation variables used in this study. CFD was utilized to initially screen the parameter ranges to reduce the number of actual experiments needed. Afterward, the residence time distribution (RTD) was determined using the respective parameters. Finally, the Fluent-predicted RTD and the experimentally measured RTD were compared. The CFD investigations revealed that an impeller speed of 50 rpm and an impeller clearance of 25 mm were not viable for experimental investigations and were thus eliminated from further analyses. The determination of RTD using a k-ε turbulence model was performed using CFD techniques. The multiple reference frame (MRF) was implemented and a steady state was initially achieved followed by a transient condition for RTD determination.

Matched MeSH terms: Hydrodynamics*
Fulltext Screening of optimization parameters for mixing process via CFD

Othman, N., Kamarudin, S.K., Mamat, M.R., Azman, A., Rosli, M.I., Takrif, M.S.

Journal of Nuclear and Related Technologies, 2013;2013(2):21-29.
MyJurnal

In this study, the numerical simulation in a mixing vessel agitated by a six bladed Rushton turbine has
been carried out to investigate the effects of effective parameters to the mixing process. The study is intended to screen the potential parameters which affect the optimization process and to provide the detail insights into the process. Three-dimensional and steady-state flow has been performed using the fully predictive Multiple Reference Frame (MRF) technique for the impeller and tank geometry. Process optimization is always used to ensure the optimum conditions are fulfilled to attain industries’ satisfaction or needs (ie; increase profit, low cost, yields, etc). In this study, the range of recommended speed to accelerate optimization is 100, 150 and 200rpm respectively and the range of recommended clearance is 50, 75 and 100mm respectively for dual Rushton impeller. Thus, the computer fluid dynamics (CFD) was introduced in order to screen the suitable parameters efficiently and to accelerate optimization. In this study,

Matched MeSH terms: Hydrodynamics
Hydrodynamic cavitation assisted degradation of persistent endocrine-disrupting organochlorine pesticide Dicofol: Optimization of operating parameters and investigations on the mechanism of intensification

Panda D, Manickam S

Ultrason Sonochem, 2019 Mar;51:526-532.
PMID: 30224289 DOI: 10.1016/j.ultsonch.2018.04.003

Dicofol, a recommended Stockholm convention persistent organic pollutants (POPs) candidate is well known for its endocrine disruptive properties and has been extensively used as an organochlorine pesticide worldwide. The hydrodynamic cavitation (HC) treatment of Dicofol in aqueous media induced by a liquid whistle hydrodynamic cavitaion reactor (LWHCR) has been investigated while considering important parameters such as inlet pressure, initial concentration of Dicofol, solution temperature, pH, addition of H2O2 and radical scavenger for the extent of degradation. The pseudo-first-order degradation rate constant (k) was determined to be 0.073 min-1 with a cavitational yield of 1.26 × 10-5 mg/J at optimum operating conditions and a complete removal of Dicofol was achieved within 1 h of treatment. Considering the removal rate and energy efficiency, the optimal inlet pressure was found to be 7 bar, resulting in a cavitation number of 0.17. High performance liquid chromatography (HPLC) and Gas chromatography mass spectroscopy (GC-MS) analyses indicated a sharp decline in the concentration of Dicofol with treatment time and indicated the presence of degraded products. An 85% total organic carbon (TOC) removal was achieved within 1 h of treatment time, demonstrating successful mineralization of Dicofol. The obtained results suggest that the degradation of Dicofol followed thermal decomposition and successive recombination reactions at bubble-vapor interface. Overall, the attempted hydrodynamic cavitation demonstrated successful and rapid removal of endocrine disruptive chemicals such as Dicofol and is expected to provide efficient solution for wastewater treatment.

Matched MeSH terms: Hydrodynamics*
Fulltext Approximating non linear higher order ODEs by a three point block algorithm

Rasedee AFN, Abdul Sathar MH, Othman KI, Hamzah SR, Ishak N

PLoS One, 2021;16(2):e0246904.
PMID: 33577619 DOI: 10.1371/journal.pone.0246904

Differential equations are commonly used to model various types of real life applications. The complexity of these models may often hinder the ability to acquire an analytical solution. To overcome this drawback, numerical methods were introduced to approximate the solutions. Initially when developing a numerical algorithm, researchers focused on the key aspect which is accuracy of the method. As numerical methods becomes more and more robust, accuracy alone is not sufficient hence begins the pursuit of efficiency which warrants the need for reducing computational cost. The current research proposes a numerical algorithm for solving initial value higher order ordinary differential equations (ODEs). The proposed algorithm is derived as a three point block multistep method, developed in an Adams type formulae (3PBCS) and will be used to solve various types of ODEs and systems of ODEs. Type of ODEs that are selected varies from linear to nonlinear, artificial and real life problems. Results will illustrate the accuracy and efficiency of the proposed three point block method. Order, stability and convergence of the method are also presented in the study.

Matched MeSH terms: Hydrodynamics
Note on dual solutions for the mixed convection boundary layer flow close to the lower stagnation point of a horizontal circular cylinder: case of constant surface heat flux

Ro?ca AV, Rosca NC, Pop I

Sains Malaysiana, 2014;43:1239-1247.

The paper reconsiders the problem of the mixed convection boundary layer flow near the lower stagnation point of a horizontal circular cylinder with a second order slip velocity model and a constant surface heat flux studied recently by RoKa et al. (2013). The ordinary (similarity) differential equations are solved numerically using the function bvp4c from Matlab for different values of the governing parameters. It is found that the similarity equations have two branches, upper and lower branch solutions, in a certain range of the mixed convection parameters. A stability analysis has been performed to show that the upper branch solutions are stable and physically realizable, while the lower branch solutions are not stable and therefore, not physically possible. This stability analysis is different by that presented by RoKa et al. (2013), who have presented a time-dependent analysis to determine the stability of the solution branches.

Matched MeSH terms: Hydrodynamics
A facile, bio-based, novel approach for synthesis of covalently functionalized graphene nanoplatelet nano-coolants toward improved thermo-physical and heat transfer properties

Sadri R, Hosseini M, Kazi SN, Bagheri S, Abdelrazek AH, Ahmadi G, et al.

J Colloid Interface Sci, 2018 Jan 01;509:140-152.
PMID: 28898734 DOI: 10.1016/j.jcis.2017.07.052

In this study, we synthesized covalently functionalized graphene nanoplatelet (GNP) aqueous suspensions that are highly stable and environmentally friendly for use as coolants in heat transfer systems. We evaluated the heat transfer and hydrodynamic properties of these nano-coolants flowing through a horizontal stainless steel tube subjected to a uniform heat flux at its outer surface. The GNPs functionalized with clove buds using the one-pot technique. We characterized the clove-treated GNPs (CGNPs) using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). We then dispersed the CGNPs in distilled water at three particle concentrations (0.025, 0.075 and 0.1wt%) in order to prepare the CGNP-water nanofluids (nano-coolants). We used ultraviolet-visible (UV-vis) spectroscopy to examine the stability and solubility of the CGNPs in the distilled water. There is significant enhancement in thermo-physical properties of CGNPs nanofluids relative those for distilled water. We validated our experimental set-up by comparing the friction factor and Nusselt number for distilled water obtained from experiments with those determined from empirical correlations, indeed, our experimental set-up is reliable and produces results with reasonable accuracy. We conducted heat transfer experiments for the CGNP-water nano-coolants flowing through the horizontal heated tube in fully developed turbulent condition. Our results are indeed promising since there is a significant enhancement in the Nusselt number and convective heat transfer coefficient for the CGNP-water nanofluids, with only a negligible increase in the friction factor and pumping power. More importantly, we found that there is a significant increase in the performance index, which is a positive indicator that our nanofluids have potential to substitute conventional coolants in heat transfer systems because of their overall thermal performance and energy savings benefits.

Matched MeSH terms: Hydrodynamics
Fulltext Synthesis, characterization, and efficacy of antituberculosis isoniazid zinc aluminum-layered double hydroxide based nanocomposites

Saifullah B, El Zowalaty ME, Arulselvan P, Fakurazi S, Webster TJ, Geilich BM, et al.

Int J Nanomedicine, 2016;11:3225-37.
PMID: 27486322 DOI: 10.2147/IJN.S102406

The chemotherapy for tuberculosis (TB) is complicated by its long-term treatment, its frequent drug dosing, and the adverse effects of anti-TB drugs. In this study, we have developed two nanocomposites (A and B) by intercalating the anti-TB drug isoniazid (INH) into Zn/Al-layered double hydroxides. The average size of the nanocomposites was found to bê164 nm. The efficacy of the Zn/Al-layered double hydroxides intercalated INH against Mycobacterium tuberculosis was increased by approximately three times more than free INH. The nanocomposites were also found to be active against Gram-positive and -negative bacteria. Compared to the free INH, the nanodelivery formulation was determined to be three times more biocompatible with human normal lung fibroblast MRC-5 cells and 3T3 fibroblast cells at a very high concentration of 50 µg/mL for up to 72 hours. The in vitro release of INH from the Zn/Al-layered double hydroxides was found to be sustained in human body-simulated buffer solutions of pH 4.8 and 7.4. This research is a step forward in making the TB chemotherapy patient friendly.

Matched MeSH terms: Hydrodynamics
Fulltext Unsteady magnetohydrodynamic free convection flow of a second grade fluid in a porous medium with ramped wall temperature

Samiulhaq, Ahmad S, Vieru D, Khan I, Shafie S

PLoS One, 2014;9(5):e88766.
PMID: 24785147 DOI: 10.1371/journal.pone.0088766

Magnetic field influence on unsteady free convection flow of a second grade fluid near an infinite vertical flat plate with ramped wall temperature embedded in a porous medium is studied. It has been observed that magnitude of velocity as well as skin friction in case of ramped temperature is quite less than the isothermal temperature. Some special cases namely: (i) second grade fluid in the absence of magnetic field and porous medium and (ii) Newtonian fluid in the presence of magnetic field and porous medium, performing the same motion are obtained. Finally, the influence of various parameters is graphically shown.

Matched MeSH terms: Hydrodynamics*
A simple and efficient sequential electrokinetic and hydrodynamic injections in micellar electrokinetic chromatography method for quantification of anticancer drug 5-fluorouracil and its metabolite in human plasma

Semail NF, Noordin SS, Keyon ASA, Waras MN, Saad B, Kamaruzaman S, et al.

Biomed Chromatogr, 2021 May;35(5):e5050.
PMID: 33314228 DOI: 10.1002/bmc.5050

A simple and sensitive preconcentration strategy using sequential electrokinetic and hydrodynamic injection modes in micellar electrokinetic chromatography with diode array detection was developed and applied for the separation and determination of anticancer agent, 5-fluorouracil and its metabolite, 5-fluoro-2'-deoxyuridine, in human plasma. Sequential injection modes with increased analyte loading capacity using the anionic pseudo-stationary phase facilitated collection of the dispersed neutral and charged analytes into narrow zones and improved sensitivity. Several important parameters affecting sample enrichment performance were evaluated and optimized in this study. Under the optimized experimental conditions, 614- and 643-fold and 782- and 803-fold sensitivity improvement were obtained for 5-fluorouracil and its metabolite when compared with normal hydrodynamic and electrokinetic injection, respectively. The method has good linearity (1-1,000 ng/ml) with acceptable coefficient of determination (r2 > 0.993), low limits of detection (0.11-0.14 ng/ml) and satisfactory analyte relative recovery (97.4-99.7%) with relative standard deviations of 4.6-9.3% (n = 6). Validation results as well as the application to analysis of human plasma samples from cancer patients demonstrate the applicability of the proposed method to clinical studies.

Matched MeSH terms: Hydrodynamics
Fulltext Superconfinement tailors fluid flow at microscales

Setu SA, Dullens RP, Hernández-Machado A, Pagonabarraga I, Aarts DG, Ledesma-Aguilar R

Nat Commun, 2015;6:7297.
PMID: 26073752 DOI: 10.1038/ncomms8297

Understanding fluid dynamics under extreme confinement, where device and intrinsic fluid length scales become comparable, is essential to successfully develop the coming generations of fluidic devices. Here we report measurements of advancing fluid fronts in such a regime, which we dub superconfinement. We find that the strong coupling between contact-line friction and geometric confinement gives rise to a new stability regime where the maximum speed for a stable moving front exhibits a distinctive response to changes in the bounding geometry. Unstable fronts develop into drop-emitting jets controlled by thermal fluctuations. Numerical simulations reveal that the dynamics in superconfined systems is dominated by interfacial forces. Henceforth, we present a theory that quantifies our experiments in terms of the relevant interfacial length scale, which in our system is the intrinsic contact-line slip length. Our findings show that length-scale overlap can be used as a new fluid-control mechanism in strongly confined systems.

Matched MeSH terms: Hydrodynamics
Fulltext Hemodynamic effects resulting from a common carotid to middle cerebral bypass with varying degrees of proximal internal carotid stenosis

Sheau, Fung Sia, Yu, Zhang, Yi, Qian, Khairul Azmi Abd Kadir, Hazman Mohd Nor, Morgan, Michael Kerin

Neurology Asia, 2014;19(3):241-247.
MyJurnal

Objective: To investigate the degree of stenosis of the internal carotid artery required for continuous blood flow in an interposition vein bypass to the middle cerebral artery. Methods: Computational fluid dynamics techniques were used to investigate a case of common carotid to middle cerebral artery brain bypass with varying degrees of internal carotid artery stenosis. Blood flow patterns across the patient-specific brain bypass were evaluated. Results: Simulation found that for cross section stenosis of less than 60%, no flow occurred in the bypass graft. Further narrowing of the internal carotid artery increased flow linearly within the bypass graft. There was significant energy loss and pressure gradient difference between the proximal and distal anastomosis sites of the bypass.
Conclusion: Computational fluid dynamics helps us to quantify the flow distribution, wall shear stress and pressure gradient in brain bypass surgery. The angle of the distal anastomosis had no effect on hemodynamic indices, allowing this consideration to be ignored in modeling. This modeling technique is useful to estimate the required degree of stenosis in the artery that is to be occluded to ensure sustained flow in the bypass. This will be of importance where there is staged surgery with a time interval between the bypass and the definitive internal carotid artery occlusion.

Matched MeSH terms: Hydrodynamics
Evaluation of the carotid artery stenosis based on minimization of mechanical energy loss of the blood flow

Sia SF, Zhao X, Li R, Zhang Y, Chong W, He L, et al.

Proc Inst Mech Eng H, 2016 Nov;230(11):1051-1058.
PMID: 28095764 DOI: 10.1177/0954411916671752

BACKGROUND: Internal carotid artery stenosis requires an accurate risk assessment for the prevention of stroke. Although the internal carotid artery area stenosis ratio at the common carotid artery bifurcation can be used as one of the diagnostic methods of internal carotid artery stenosis, the accuracy of results would still depend on the measurement techniques. The purpose of this study is to propose a novel method to estimate the effect of internal carotid artery stenosis on the blood flow based on the concept of minimization of energy loss.
METHODS: Eight internal carotid arteries from different medical centers were diagnosed as stenosed internal carotid arteries, as plaques were found at different locations on the vessel. A computational fluid dynamics solver was developed based on an open-source code (OpenFOAM) to test the flow ratio and energy loss of those stenosed internal carotid arteries. For comparison, a healthy internal carotid artery and an idealized internal carotid artery model have also been tested and compared with stenosed internal carotid artery in terms of flow ratio and energy loss.
RESULTS: We found that at a given common carotid artery bifurcation, there must be a certain flow distribution in the internal carotid artery and external carotid artery, for which the total energy loss at the bifurcation is at a minimum; for a given common carotid artery flow rate, an irregular shaped plaque at the bifurcation constantly resulted in a large value of minimization of energy loss. Thus, minimization of energy loss can be used as an indicator for the estimation of internal carotid artery stenosis.

Matched MeSH terms: Hydrodynamics
Permeability studies of artificial and natural cancellous bone structures

Syahrom A, Abdul Kadir MR, Abdullah J, Öchsner A

Med Eng Phys, 2013 Jun;35(6):792-9.
PMID: 22959618 DOI: 10.1016/j.medengphy.2012.08.011

In the development of artificial cancellous bones, two major factors need to be considered: the integrity of the overall structure and its permeability. Whilst there have been many studies analysing the mechanical properties of artificial and natural cancellous bones, permeability studies, especially those using numerical simulation, are scarce. In this study, idealised cancellous bones were simulated from the morphological indices of natural cancellous bone. Three different orientations were also simulated to compare the anisotropic nature of the structure. Computational fluid dynamics methods were used to analyse fluid flow through the cancellous structures. A constant mass flow rate was used to determine the intrinsic permeability of the virtual specimens. The results showed similar permeability of the prismatic plate-and-rod model to the natural cancellous bone. The tetrakaidecahedral rod model had the highest permeability under simulated blood flow conditions, but the plate counterpart had the lowest. Analyses on the anisotropy of the virtual specimens showed the highest permeability for the horizontal orientation. Linear relationships were found between permeability and the two physical properties, porosity and bone surface area.

Matched MeSH terms: Hydrodynamics
Fulltext A Facile and Flexible Method for On-Demand Directional Speed Tunability in the Miniaturised Lab-on-a-Disc

Tan MK, Siddiqi A, Yeo LY

Sci Rep, 2017 07 27;7(1):6652.
PMID: 28751783 DOI: 10.1038/s41598-017-07025-x

The Miniaturised Lab-on-a-Disc (miniLOAD) platform, which utilises surface acoustic waves (SAWs) to drive the rotation of thin millimeter-scale discs on which microchannels can be fabricated and hence microfluidic operations can be performed, offers the possibility of miniaturising its larger counterpart, the Lab-on-a-CD, for true portability in point-of-care applications. A significant limitation of the original miniLOAD concept, however, is that it does not allow for flexible control over the disc rotation direction and speed without manual adjustment of the disc's position, or the use of multiple devices to alter the SAW frequency. In this work, we demonstrate the possibility of achieving such control with the use of tapered interdigitated transducers to confine a SAW beam such that the localised acoustic streaming it generates imparts a force, through hydrodynamic shear, at a specific location on the disc. Varying the torque that arises as a consequence by altering the input frequency to the transducers then allows the rotational velocity and direction of the disc to be controlled with ease. We derive a simple predictive model to illustrate the principle by which this occurs, which we find agrees well with the experimental measurements.

Matched MeSH terms: Hydrodynamics
Low-gradient magnetic separation of magnetic nanoparticles under continuous flow: Experimental study, transport mechanism and mathematical modelling

Tan YW, Leong SS, Lim J, Yeoh WM, Toh PY

Electrophoresis, 2022 Nov;43(21-22):2234-2249.
PMID: 35921231 DOI: 10.1002/elps.202200078

Low-gradient magnetic separation (LGMS) of magnetic nanoparticles (MNPs) has been proven as one of the techniques with great potential for biomedical and environmental applications. Recently, the underlying principle of particle capture by LGMS, through a process known as magnetophoresis, under the influence of hydrodynamic effect has been widely studied and illustrated. Even though the hydrodynamic effect is very substantial for batch processes, its impact on LGMS operated at continuous flow (CF) condition remained largely unknown. Hence, in this study, the dynamical behaviour of LGMS process operated under CF was being studied. First, the LGMS experiments using poly(sodium 4-styrenesulfonate)-functionalized-MNP as modelled particle system were performed through batchwise (BW) and CF modes at different operating conditions. Here BW operation was used as a comparative study to elucidate the transport mechanism of MNP under the similar environment of CF-LGMS process, and it was found out that the convection induced by magnetophoresis (timescale effective is ∼1200 s) is only significant at far-from-magnet region. Hence, it can be deduced that forced convection is more dominant on influencing the transport behaviour of CF-LGMS (with resident time ≤240 s). Moreover, we found that the separation efficiency of CF-LGMS process can be boosted by the higher number of magnets, the higher MNP concentration and the lower flowrate of MNP solution. To better illustrate the underlying dynamical behaviour of LGMS process, a mathematical model was developed to predict its kinetic profile and separation efficiency (with average error of ∼2.6% compared to the experimental results).

Matched MeSH terms: Hydrodynamics
Electrokinetic supercharging in nonaqueous capillary electrophoresis for online preconcentration and determination of tamoxifen and its metabolites in human plasma

Thang LY, Breadmore MC, See HH

J Chromatogr A, 2016 Jul 27.
PMID: 27485148 DOI: 10.1016/j.chroma.2016.07.067

An online preconcentration method, namely electrokinetic supercharging (EKS), was evaluated for the determination of tamoxifen and its metabolites in human plasma in nonaqueous capillary electrophoresis with ultraviolet detection (NACE-UV). This method was comprehensively optimized in terms of the leading electrolyte (LE) and terminating electrolyte (TE) injection lengths, as well as electrokinetic sample injection time. The optimized EKS conditions employed were as follows: hydrodynamic injection (HI) of 10mM potassium chloride as LE at 150mbar for 36s (4% of total capillary volume). The sample was injected at 10kV for 300s, followed by HI of 10mM pimozide as TE at 150mbar for 36s (4% of total capillary volume). Separation was performed in 7.5mM deoxycholic acid sodium salt, 15mM acetic acid and 1mM 18-crown-6 in 100% methanol at +25kV with UV detection at 205nm. Under optimized conditions, the sensitivity was enhanced between 160- and 600-fold when compared with our previously developed method based on HI at 150mbar for 12s. The detection limit of the method for tamoxifen and its metabolites were 0.05-0.25ng/mL, with RSDs between 2.1% and 3.5%. Recoveries in spiked human plasma were 95.6%-99.7%. A comparison was also made between the proposed EKS approach and the standard field-amplified sample injection (FASI) technique. EKS proved to be 3-5 times more sensitive than the FASI. The new EKS method was applied to the analysis of tamoxifen and its metabolites in plasma samples from breast cancer patients after liquid-liquid extraction.

Matched MeSH terms: Hydrodynamics
Fulltext Theoretical development and critical analysis of burst frequency equations for passive valves on centrifugal microfluidic platforms

Thio TH, Soroori S, Ibrahim F, Al-Faqheri W, Soin N, Kulinsky L, et al.

Med Biol Eng Comput, 2013 May;51(5):525-35.
PMID: 23292292 DOI: 10.1007/s11517-012-1020-7

This paper presents a theoretical development and critical analysis of the burst frequency equations for capillary valves on a microfluidic compact disc (CD) platform. This analysis includes background on passive capillary valves and the governing models/equations that have been developed to date. The implicit assumptions and limitations of these models are discussed. The fluid meniscus dynamics before bursting is broken up into a multi-stage model and a more accurate version of the burst frequency equation for the capillary valves is proposed. The modified equations are used to evaluate the effects of various CD design parameters such as the hydraulic diameter, the height to width aspect ratio, and the opening wedge angle of the channel on the burst pressure.

Matched MeSH terms: Hydrodynamics
Effects of aqueous humor hydrodynamics on human eye heat transfer under external heat sources

Tiang KL, Ooi EH

Med Eng Phys, 2016 Aug;38(8):776-84.
PMID: 27340100 DOI: 10.1016/j.medengphy.2016.05.011

The majority of the eye models developed in the late 90s and early 00s considers only heat conduction inside the eye. This assumption is not entirely correct, since the anterior and posterior chambers are filled aqueous humor (AH) that is constantly in motion due to thermally-induced buoyancy. In this paper, a three-dimensional model of the human eye is developed to investigate the effects AH hydrodynamics have on the human eye temperature under exposure to external heat sources. If the effects of AH flow are negligible, then future models can be developed without taking them into account, thus simplifying the modeling process. Two types of external thermal loads are considered; volumetric and surface irradiation. Results showed that heat convection due to AH flow contributes to nearly 95% of the total heat flow inside the anterior chamber. Moreover, the circulation inside the anterior chamber can cause an upward shift of the location of hotspot. This can have significant consequences to our understanding of heat-induced cataractogenesis.

Matched MeSH terms: Hydrodynamics*
Rheological and fractal hydrodynamics of aerobic granules

Tijani HI, Abdullah N, Yuzir A, Ujang Z

Bioresour Technol, 2015 Jun;186:276-85.
PMID: 25836036 DOI: 10.1016/j.biortech.2015.02.107

The structural and hydrodynamic features for granules were characterized using settling experiments, predefined mathematical simulations and ImageJ-particle analyses. This study describes the rheological characterization of these biologically immobilized aggregates under non-Newtonian flows. The second order dimensional analysis defined as D2=1.795 for native clusters and D2=1.099 for dewatered clusters and a characteristic three-dimensional fractal dimension of 2.46 depicts that these relatively porous and differentially permeable fractals had a structural configuration in close proximity with that described for a compact sphere formed via cluster-cluster aggregation. The three-dimensional fractal dimension calculated via settling-fractal correlation, U∝l(D) to characterize immobilized granules validates the quantitative measurements used for describing its structural integrity and aggregate complexity. These results suggest that scaling relationships based on fractal geometry are vital for quantifying the effects of different laminar conditions on the aggregates' morphology and characteristics such as density, porosity, and projected surface area.

Matched MeSH terms: Hydrodynamics

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