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LAMINAR PULSATING CONFINED JET FLOW OF NANOFLUIDS IN A DUCT WITH ISOFLUX WALL

HEAT TRANSFER RESEARCH 2017年第11期48卷 1007-1024页

作者： Rahgoshay, M. Ranjbar, A. A. Ramiar, A. Rahimi, M. Arya, A. Babol Univ Technol Sch Mech Engn POB 484 Babol Sar Iran

Pulsating flows have a potential for research in many aspects. A pulsating unsteady confined jet is still unclear and requires further investigation because of many upcoming applications. In the past decade, nanofluids have attracted much interest because of their reported superior thermal performance and many potential applications. Also, a pulsating confined jet in a nanofluid is a new idea in fluid mechanics and heat transfer. In this paper, two-dimensional pulsating confined jet flow of nanofluids through a duct with isoflux walls is investigated numerically. In order to solve the Navier-Stokes and energy equations, the finite volume approach with collocated grid is employed. The momentum interpolation technique of Rhie and Chow is applied in simple algorithm. The simulation is performed at different pulse parameters (amplitude, Strouhal and Reynolds numbers) and volume fractions of nanoparticles for unsteady flow and also various values of the duct-to-jet width ratio (aspect ratio). Increasing both the frequency and amplitude leads to a slight increase in the Nusselt number but by increasing the Reynolds number, aspect ratio, and volume fraction the average Nusselt number will increase more. By increasing the Reynolds number and volume fraction, a higher rate of heat transfer is observed. The authors have not found in the open literature any records similar to the present work. One of the advantages of using pulsation in a nanofluid is a delay in the sedimentation process of nanoparticles.

关键词： pulsating flow Strouhal number volume fraction recirculation zone Nusselt number simple algorithm nanofluid

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APPLICATION OF A NEW SINGLE STAGGERED GRID METHOD TO THE HEAT TRANSFER PROBLEMS

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THERMAL SCIENCE 2019年第Sup3期23卷 S631-S637页

作者： Liang, Xin Liu, Guan-Nan China Univ Min & Technol Key Lab Coal Based Capture & Geol Storage Jiangsu Xuzhou Jiangsu Peoples R China China Univ Min & Technol State Key Lab GeoMech & Deep Underground Engn Xuzhou Jiangsu Peoples R China China Univ Min & Technol Sch Mech & Civil Engn Xuzhou Jiangsu Peoples R China

In this paper, a new single staggered grid method is proposed to solve the fluid dynamic problems numerically. The advantages of the new grid method are analyzed in comparison with the classical grid algorithms such as the staggered grids, collocated grids and semi-staggered grids. The discretization of the basic equations for the fluid dynamics on the new single staggered grids is derived and the corresponding simple algorithm is introduced. As an example, the heat transfer problem offluid-flow at a right angle is solved to prove the validity of the new single staggered grid method.

关键词： single staggered grid method simple algorithm fluid dynamics heat transfer problem

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A new implicit fictitious domain method for the simulation of flow in complex geometries with heat transfer

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JOURNAL OF COMPUTATIONAL PHYSICS 2013年 237卷 21-45页

作者： Haeri, S. Shrimpton, J. S. Univ Southampton Sch Engn Sci Southampton SO17 1BJ Hants England

A numerical algorithm for the simulation of flow past immersed objects with heat transfer is proposed and validated which conforms with the ideas of the fictitious domain method. A momentum source term is added to account for the presence of the object and a heat source term is proposed to impose the Dirichlet boundary condition on the surface of the objects. The algorithm is an implicit fictitious domain based method where the entire fluid-immersed object domain assumed to be an incompressible fluid. The flow domain is constrained to be divergence free, whereas a rigidity constraint is imposed on the body domain. Heat transfer is similarly considered by assuming that the object domain is filled with a fluid with different thermal properties. The simple algorithm with a collocated grid arrangement is used for pressure-velocity coupling which is unconditionally stable. The algorithm is validated by considering stationary, forced motion and freely moving objects with both isothermal and freely variable temperature inside the object. Good agreement with previous numerical and experimental studies for all the test cases is observed. (c) 2012 Elsevier Inc. All rights reserved.

关键词： Fictitious domain Forced convection Free convection simple algorithm Collocated grid

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SOLUTAL CONVECTION AND MASS-TRANSFER IN INCLINED ENCLOSURES

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 1995年第2期9卷 262-269页

作者： GAU, C JENG, DZ National Cheng Kung Univ. Tainan Taiwan

Both experimental and numerical work are performed to study the solutal convection now and transport process in the enclosures that can be inclined at different angles, The enclosure is filled with an aqueous solution containing CuSO4 + H2SO4, where the flow structure is visualized by both a particle tracer and shadowgraph, With a nonintrusive optical method the concentration fluctuations at desired locations are measured, The mass transfer Sherwood numbers across the enclosure at various inclinations are also measured and the results are correlated in terms of relevant nondimensional parameters, In the experiments, the Rayleigh number ranges from 1.126 x 10(8) to 1.157 x 10(11), the Schmidt numbers from 2500 to 3989, the angles of inclination from 30 to 150 deg, and the aspect ratios of the enclosure from 0.25 to 1, The simple algorithm developed by Patankar is employed to calculate the solutal convection, and the results are compared with the data. It was found that both the inclination and the aspect ratio of the enclosure have a significant effect on the now structure and mass transfer, For a large angle of inclination, the accumulation of solutal boundary-layer flow leads to stratification of the core and reduction of the mass transfer, For a small inclination, generation and protrusion of solutal plumes leads to oscillation of concentration and enhancement of mass transfer.

关键词： Natural Convection Mass Transfer Coefficient High Aspect Ratio Boundary Layer Thickness Schmidt Numbers simple algorithm Heat Transfer Correlations Buoyancy Force Flow Patterns Boussinesq Approximation

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Automated analysis of fatality rates for COVID 19 across different countries

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ALEXANDRIA ENGINEERING JOURNAL 2021年第1期60卷 521-526页

作者： Jabbar, Shaima Ibraheem Al Furat Al Awsat Tech Univ Babylon Tech Inst Babylon Iraq

One of the significant parameters that helps in the reporting the highest risk areas, which have COVID 19 pandemic is case fatality rate (CFR). In this work, automated analysis was carried out to evaluate fatality rate (CFR) across different countries. Furthermore, a state of art algorithm is proposed to estimate CFR and it is possible to make it applicable in the mobile phone. This application will enable us to monitor the status level of the patients (suspected, exposed and infected) to save time, efforts and get a high quailty of the recordings. All data were obtained from (https://***/coronavirus/) and pointed at the period between 27th March and 27th May 2020. Results present Spain and Egypt have a highest score of the fatality rate (approximately 24%) compared with previous research, which Italy was the highest score of the case fatality rate (CFR). On the other hand, Australia has had the lowest of the (CFR) in the current and previous researches. Furthermore, Spain has the highest percentage score of the total active cases and death rate: 0.41% and 0.00073% respectively. Documentation and comparison fatality rate of COVID 19 pandemic across different countries could assist in illustrating the strength of this pandemic, speed spreading and risk area which infected of this disease. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University.

关键词： COVID 19 Case fatality rate (CFR) Health services simple algorithm Prediction

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Time-dependent economic risk analysis of the natural gas transmission pipeline system

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PROCESS SAFETY AND ENVIRONMENTAL PROTECTION 2021年 146卷 432-440页

作者： Shi, Guoyun Yu, Weichao Wang, Kun Dang, Fuhua Gong, Jing Lu, Yanan China Univ Petr Beijing Key Lab Urban Oil & Gas Distribut Technol Natl Engn Lab Pipeline Safety MOE Key Lab Petr Engn Beijing 102249 Peoples R China China Petr Planning & Engn Inst Beijing 10083 Peoples R China Oriental Huazhi Petr Engn Co Ltd Tianjin 301700 Peoples R China China Natl Petr Corp East Branch Nat Gas Mkt Co Shanghai 200120 Peoples R China

A methodology to quantify the economic risk of a natural gas transmission pipeline system is developed in this study, and the effect of the line pack is considered. The methodology is based on the risk theory and hydraulic analysis of the transmission pipeline system. In the methodology, the failure probability of the key components in the transmission pipeline system are estimated firstly. Moreover, the transient compressible model for the pipeline system is employed to perform the consequence analysis, and the model is solved by the Semi-Implicit Method for Pressure-Linked Equation (simple) algorithm in the process of the consequence analysis. By combining the failure probability estimation with the consequence analysis, the economic risk when an accident happens can be evaluated. A detailed procedure for economic risk evaluation of a natural gas transmission pipeline system is presented, and its feasibility is confirmed with a real transmission pipeline system. Furthermore, impacts of the line pack on the economic risk are investigated, and suggestions to decrease the economy risk are proposed. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

关键词： Economic risk Line pack Failure probability Gas pipeline Compressible fluid simple algorithm

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Optimum Interaction Between Magnetohydrodynamics and Nanofluid for Thermal and Drag Management

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2017年第1期31卷 218-229页

作者： Bovand, M. Rashidi, S. Esfahani, J. A. Islamic Azad Univ Energy & Sustainable Dev Res Ctr Semnan Branch POB 35196-97951 Semnan Iran Ferdowsi Univ Mashhad Dept Mech Engn Mashhad 917751111 Iran

The magnetohydrodynamic technique has a positive impact upon the reduction of the unsteady flow forces, and a negative effect on the thermal performance. Adding nanoparticles to the base fluid is a common technique for thermal-performance improvement that can lead to an increase in drag forces. This paper is an attempt to control and optimize the interactions between two techniques by response surface methodology for nanofluid flow around a triangular obstacle. Also, a sensitivity analysis is performed to determine which parameters are the key drivers of a model's results. Orientations of the obstacle, Stuart number, and volumetric concentration of nanoparticles are selected as the operational parameters. A finite volume method with computational fluid dynamics techniques is used to solve the governing equations. The ranges of Stuart number N, orientations of the triangular obstacle , and volumetric concentration of nanoparticles phi are 0-5, 0-60deg, and 0-0.05, respectively. The Reynolds number Re is fixed at Re=100. The obtained results indicate that the Nusselt number Nu is more sensitive to the Stuart number rather than the orientations of the obstacle or the volumetric concentration of nanoparticles. Also, the optimized parameters for the minimum drag coefficient C-D are N=0.1697, theta=54.543deg, and phi=0.0225. These values for the maximum Nusselt number are N=0, theta=35.151deg, and phi=0.05.

关键词： Nanofluids Magnetohydrodynamics Enhancing Heat Transfer Rate Drag Coefficient Stuart Numbers Nanoparticles simple algorithm Sensitivity Analysis Finite Volume Method Unsteady Flows

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Sensitivity of mixed subsonic-supersonic turbulent mixing layers

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JOURNAL OF PROPULSION AND POWER 2001年第4期17卷 823-835页

作者： Cottrell, DC Plesniak, MW Purdue Univ Sch Mech Engn Maurice J Zucrow Labs W Lafayette IN 47907 USA

Numerical predictions of compressible turbulent mixing layers have been performed for convective Mach numbers up to 0.7 (M-C less than or equal to0.7), This flow is particularly challenging to compute because the mixing layer consists of one supersonic stream and one subsonic stream, resulting in a mixed hyperbolic/elliptic solution. The FLUENT (C) computational fluid dynamics code, which incorporates a renormalization group k-is an element of turbulence model and the simpleC solution algorithm, was used to perform the computations. Initially, predictions were performed for several different convective Mach numbers (M-C = 0.2, 0.5, and 0.7), and the computed results (mixing layer thickness, mean velocity, and turbulence parameters) were compared with experiments to benchmark the code. Following this qualification procedure, the sensitivity of the Me = 0.7 case to disturbances was further investigated by introducing small perturbations to the boundary conditions and recomputing the mixing layer. Specifically, effects of perturbations to the secondary stream stagnation pressure and test section wall adjustment angle were investigated, It was found that the compressible mixing layer growth rate was significantly altered by small changes (<4%) in the secondary stream stagnation pressure. In addition, divergence or convergence of the test section walls of less than 3 deg resulted in appreciable changes in the streamwise pressure gradient and mixing layer development.

关键词： Turbulent Mixing Adverse Pressure Gradient simple algorithm Kinematic Viscosity Freestream Velocity Kinetic Energy Stress Distribution Solution algorithm Turbulence Models Turbulent Boundary Layer

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Mixed convection in thermally anisotropic non-Darcy porous medium in double lid-driven cavity using Bejan's heatlines

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ALEXANDRIA ENGINEERING JOURNAL 2016年第1期55卷 299-309页

作者： Ahmed, Sameh E. South Valley Univ Dept Math Fac Sci Qena 83523 Egypt

This paper discusses the problem of mixed convection in two-sided lid-driven enclosures saturated non-Darcy porous medium. The vertical walls of the cavity were kept thermally insulated. The bottom wall is cooled while the top wall is uniformly heated. The bottom and the top walls are moving in opposite direction. The governing equations were solved using finite volume method with simple algorithm. A new form for the heat function was derived. The obtained results were presented in contours maps for the streamlines, the isotherms and the heat function. The profiles of the horizontal velocity component and the maximum values of vertical velocity components as well as the mean Nusselt number were presented graphically. It is found that, for the low values of the Richardson number, the forced convection plays a dominant role in the flow region. The increase in inverse Darcy number leads to decrease the mean Nusselt number. (C) 2015 Faculty of Engineering, Alexandria University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons. org/licenses/by-nc-nd/4.0/).

关键词： Heatlines Lid-driven Non-Darcy Heat generation simple algorithm

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Numerical simulation of buckling and asymmetric behavior of flexible filament using temporal second-order immersed boundary method

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INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT & FLUID FLOW 2020年第3期30卷 1047-1095页

作者： Kanchan, Mithun Maniyeri, Ranjith Natl Inst Technol Dept Mech Engn Surathkal India

Purpose The purpose of this paper is to perform two-dimensional numerical simulation involving fluid-structure interaction of flexible filament. The filament is tethered to the bottom of a rectangular channel with oscillating fluid flow inlet conditions at low Reynolds number. The simulations are performed using a temporal second-order finite volume-based immersed boundary method (IBM). Further, to understand the relation between different aspect ratios i.e. ratio of filament length to channel height (Len/H) and fixed channel geometry ratio, i.e. ratio of channel height to channel length (H/Lc) on mixing and pumping capabilities. Design/methodology/approach The discretization of governing continuity and Navier-Stokes equation is done by finite-volume method on a staggered Cartesian grid. simple algorithm is used to solve fluid velocity and pressure terms. Two cases of oscillatory flow conditions are used with the flexible filament tethered at the center of bottom channel wall. The first case is sinusoidal oscillatory flow with phase shift (SOFPS) and second case is sinusoidal oscillatory flow without phase shift (SOF). The simulation results are validated with filament dynamics studies of previous researchers. Further, parametric analysis is carried to study the effect of filament length (aspect ratio), filament bending rigidity and Reynolds number on the complex deformation and behavior of flexible filament interacting with nearby oscillating fluid motion. Findings It is found that selection of right filament length and bending rigidity is crucial for fluid mixing scenarios. The phase shift in fluid motion is also found to critically effect filament displacement dynamics, especially for rigid filaments. Aspect ratio, suitable for mixing applications is dependent on channel geometry ratio. Symmetric deformation is observed for filaments subjected to SOFPS condition irrespective of bending rigidity, whereas medium and low rigidity filaments placed in SOF condition sh

关键词： Finite volume method Immersed boundary method Flexible filament Low Reynolds number simple algorithm

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