A Numerical and Experimental Study of Laminar Unsteady Lid-Driven Cavity Flows

2017 ◽  
Author(s):  
K. M. Akyuzlu
Keyword(s):  
Experimental Study ◽  
Steady State ◽  
Flow Field ◽  
Numerical Study ◽  
Working Fluid ◽  
Cavity Flows ◽  
Square Cavity ◽  
Measured Velocity ◽  
Driven Cavity ◽  
Numerical Predictions

An experimental and numerical study was conducted to study unsteady lid-driven cavity flows. More specifically, the development of the circulation patterns inside a square cavity due to the movement of a rigid impermeable lid at constant velocity was observed experimentally and predicted numerically by CFD codes. Particle Image Velocimeter (PIV) technique was used to determine the flow field as it develops from stagnation to steady state inside a one inch (25.4 mm) square cavity driven by an impermeable lid. To avoid the three dimensional effects on the primary vortex, the depth of the cavity is taken to be 5 inches (127 mm). Working fluid is water and it is seeded with hallow glass spheres with 10 microns diameter. Experimental study was conducted for different lid velocities corresponding to Reynolds numbers for laminar to intermittent turbulence. The numerical study was carried out using commercial and in-house CFD codes for the steady state case, and using a commercial CFD code for the unsteady case. The predictions of unsteady flow field inside the two-dimensional square cavity were made using these codes which employ second order accurate (temporally and spatially) implicit numerical schemes. A time and mesh independence study was carried out to determine the optimum mesh size and time increment for the unsteady case study. Comparisons of the numerically predicted and experimentally measured velocity fields are made for steady and unsteady cases. The results indicate that the numerical predictions capture the characteristics of the circulation inside the cavity reasonably well however the magnitude of the velocities are underestimated.

A Study of Formation of Circulation Patterns in Laminar Unsteady Lid-Driven Cavity Flows Using PIV Measurement Techniques

2012 ◽  
Author(s):  
K. M. Akyuzlu ◽  
J. Farkas
Keyword(s):  
Steady State ◽  
Measurement Techniques ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Computational Fluid Mechanics ◽  
Square Cavity ◽  
Driven Cavity ◽  
Circulation Patterns ◽  
Piv Measurement ◽  
Steady State Predictions

An experimental study was conducted to observe/visualize, the formation of circulation patterns inside a square cavity due to the movement of a lid at constant velocity. Lid driven cavity flow is one of the benchmark studies used in the verification/improvement of CFD codes for internal flow applications/predictions. Previous work on this topic is primarily focused on improving the steady state predictions of the CFD codes using different numerical schemes and algorithms. Furthermore, almost all of the studies reported in computational fluid mechanics literature relates to steady state predictions of lid or shear driven flows. Experimental work that is reported in these studies is limited in scope and number. This paper reports on the measurements we made using Particle Image Velocimeter (PIV) technique to determine the flow field as it develops from stagnation to steady state inside a square cavity driven by a lid. For this purpose, we employed a 2-D PIV system, which uses a double-cavity, Nd:Yag laser to illuminate the test cavity. Experiments were conducted using water as the working fluid inside a square cavity that is one inch (25.4 mm) high and one inch wide. The depth of the cavity is five inches (127 mm) to ensure two-dimensional circulations patterns. Hollow glass sphere particles with 10 microns in diameter were used as seeding of the working fluid, water. Experiments were repeated for different lid velocities corresponding to lid Reynolds numbers (laminar to beginning of transition of turbulence.) Velocity fields were captured during the development of the circulations patters each being unique for the time of the measurement and value of the lid velocity. The center of the circulation pattern and its path inside the cavity is constructed from the captured images as steady state is attained. Also, the strength of the circulation (as manifested by the increase in the diameter of the circulation) is determined at different times for different Reynolds numbers.

Experimental and Numerical Study of Methanol-Water Mixture Single-Phase Heat Transfer in a Micro-Channel Heat Sink

2012 ◽  
Author(s):  
Chun K. Kwok ◽  
Matthew M. Asada ◽  
Jonathan R. Mita ◽  
Weilin Qu
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Sink ◽  
Single Phase ◽  
Numerical Study ◽  
Pure Water ◽  
Molar Fraction ◽  
Water Mixture ◽  
Micro Channel ◽  
Numerical Predictions

This paper presents an experimental study of single-phase heat transfer characteristics of binary methanol-water mixtures in a micro-channel heat sink containing an array of 22 microchannels with 240μm × 630μm cross-section. Pure water, pure methanol, and five methanol-water mixtures with methanol molar fraction of 16%, 36%, 50%, 63% and 82% were tested. Key parametric trends were identified and discussed. The experimental study was complemented by a three-dimensional numerical simulation. Numerical predictions and experimental data are in good agreement with a mean absolute error (MAE) of 0.87%.

Experimental and Numerical Study of Transport Phenomena in a Simulated Hydrothermal Crystal Growth System of Fluid-Saturated Porous Layer

2000 ◽  
Author(s):  
D. Mishra ◽  
A. Pal ◽  
N. Nemick ◽  
A. K. Saha ◽  
V. Prasad ◽  
...  
Keyword(s):  
Temperature Field ◽  
Porous Layer ◽  
Hydrothermal System ◽  
Numerical Study ◽  
Transport Phenomena ◽  
Composite Layer ◽  
Staggered Grid ◽  
Working Fluid ◽  
Hydrothermal Crystal Growth ◽  
Numerical Predictions

Abstract A simulated, non-pressurized hydrothermal system consisting of a fluid-superposed porous layer is fabricated and used for visualization and measurement of the temperature field using liquid crystal thermography. The system is used for various boundary conditions with pure glycerine as the working fluid and the porous layer is made of 3mm diameter glass beads. Experimental data is recorded using a color CCD camera and flow visualization is obtained through a long exposure video photography. A calibration is performed to relate the temperature with scattered colors at an orthogonal angle to the incoming white light sheet. Quantitative temperature data is obtained through this calibration and compared with the numerical predictions. For numerical studies the system is modeled as a composite layer of fluid and porous charge using the Darcy-Brinkman-Forchheimer flow model. A two-dimensional curvilinear algorithm using finite volume technique with a non-staggered grid is used to simulate the temperature field and transport phenomena for various Rayleigh–Darcy number combinations of varying aspect ratio. The results, for the first time, make an attempt towards understanding the transport process in hydrothermal system through both numerical simulation and experimental validation.

scholarly journals Experimental and Numerical Study on Energy Piles with Phase Change Materials

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4699 ◽  
Author(s):  
M. M. Mousa ◽  
A. M. Bayomy ◽  
M. Z. Saghir
Keyword(s):  
Phase Change ◽  
Heat Pump ◽  
Flow Rate ◽  
Phase Change Materials ◽  
Numerical Study ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Numerical Predictions ◽  
Energy Piles ◽  
Discharging Capacity

Phase change materials (PCM) utilization in energy storage systems represents a point of interest and attraction for the researchers to reduce greenhouse gas emissions. PCM have been used widely on the interior or exterior walls of the building application to optimize the energy consumption during heating and cooling periods. Meanwhile, ground source heat pump (GSHP) gained its popularity because of the high coefficient of performance (COP) and low running cost of the system. However, GSHP system requires a stand-by heat pump during peak loads. This study will present a new concept of energy piles that used PCM in the form of enclosed tube containers. A lab-scaled foundation pile was developed to examine the performance of the present energy pile, where three layers of insulation replaced the underground soil to focus on the effect of PCM. The investigation was conducted experimentally and numerically on two identical piles with and without PCM. Moreover, a flow rate parametric study was conducted to study the effect of the working fluid flow rate on the amount of energy stored and released at each model. Finally, a comprehensive Computational fluid dynamic (CFD) model was developed and compared with the experimental results. There was a good agreement between the experimental measurements and the numerical predictions. The results revealed that the presence of PCM inside the piles increased not only the charging and discharging capacity but also the storage efficiency of the piles. It was found that PCM enhances the thermal response of the concrete during cooling and heating processes. Although increasing the flow rate increased charging and discharging capacity, the percentage of energy stored/released was insignificant compared to the flow rate increasing percentage.

Effect of Surface Radiation on Multiple Natural Convection Solutions in a Square Cavity Partially Heated from Below

2006 ◽  
Vol 128 (10) ◽  
pp. 1012-1021 ◽  
Author(s):  
El Hassan Ridouane ◽  
Mohammed Hasnaoui
Keyword(s):  
Steady State ◽  
Natural Convection ◽  
Numerical Study ◽  
Heated Surface ◽  
Steady State Solution ◽  
Surface Radiation ◽  
Bottom Wall ◽  
Square Cavity ◽  
Square Enclosure ◽  
Surface Dimension

A numerical study of natural convection with surface radiation in an air filled square enclosure with a centrally heated bottom wall and cooled upper wall is presented. The vertical walls and the rest of the bottom wall are assumed to be insulated. The problem is studied for Rayleigh numbers Ra, ranging from 103 to 4×106 and surfaces emissivity ε, varying from 0 to 1. The governing equations, written in terms of stream function-vorticity formulation, are solved using a finite difference approach. It is found that, under these heating/cooling conditions, three different steady-state solutions are possible in the ranges of the parameters considered. Results are presented detailing the occurrence of each steady-state solution and the effect of Ra and ε on its range of existence. It is found that the surface radiation alters significantly the existence ranges of the solutions. For each solution, convective and radiative contributions to the global heat transfer are also quantified for various Ra and ε. The influence of the heated surface dimension on the fluid flow and thermal patterns is also presented by comparing the present results against those obtained by the authors in an earlier study within a square cavity totally heated from below.

A Numerical Study of Turbulent Flow Characteristics of Servo-Valve Orifices

1989 ◽  
Vol 203 (2) ◽  
pp. 139-147 ◽  
Author(s):  
D C Pountney ◽  
W Weston ◽  
M R Banieghbal
Keyword(s):  
Experimental Study ◽  
Turbulent Flow ◽  
Numerical Scheme ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Flow Patterns ◽  
Servo Valve ◽  
Valve Orifice ◽  
Numerical Predictions

A numerical scheme based on the k—e turbulences model has been employed to determine turbulent flow characteristics of servo-valve orifices. Numerical predictions of flow patterns, flow coefficients and pressure variations within the valve orifice are presented and their implications for control of spool forces and cavitation effects are considered. The limitations of the model are considered and a proposal for more effective servo-valve modelling, together with a comparable experimental study, is made.

scholarly journals Prandtl Number Effects on the Entropy Generation During the Transient Mixed Convection in a Square Cavity Heated from Below

2021 ◽  
Author(s):  
Nawal Ferroudj ◽  
Hasan Koten ◽  
Sacia Kachi ◽  
Saadoun Boudebous
Keyword(s):  
Heat Transfer ◽  
Prandtl Number ◽  
Mixed Convection ◽  
Entropy Generation ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Working Fluid ◽  
Square Cavity ◽  
Nusselt Numbers ◽  
The Impact

This numerical study considers the mixed convection, heat transfer and the entropy generation within a square cavity partially heated from below with moving cooled vertical sidewalls. All the other horizontal sides of the cavity are assumed adiabatic. The governing equations, in stream function–vorticity form, are discretized and solved using the finite difference method. Numerical simulations are carried out, by varying the Richardson number, to show the impact of the Prandtl number on the thermal, flow fields, and more particularly on the entropy generation. Three working fluid, generally used in practice, namely mercury (Pr = 0.0251), air (Pr = 0.7296) and water (Pr = 6.263) are investigated and compared. Predicted streamlines, isotherms, entropy generation, as well as average Nusselt numbers are presented. The obtained results reveal that the impact of the Prandtl number is relatively significant both on the heat transfer performance and on the entropy generation. The average Nusselt number increase with increasing Prandtl number. Its value varies thereabouts from 3.7 to 3.8 for mercury, from 5.5 to 13 for air and, from 12.5 to 15 for water. In addition, it is found that the total average entropy generation is significantly higher in the case of mercury (Pr«1) and water (Pr»1) than in the case of air (Pr~1). Its value varies approximately from 700 to 1100 W/m3 K for mercury, from 200 to 500 W/m3 K for water and, from 0.03 to 5 W/m3 K for air.    

Study on Vortex Evolution Processes of Transient Driven Flow in a Square Cavity

2014 ◽  
Vol 670-671 ◽  
pp. 751-754
Author(s):  
Shi Hua He ◽  
Li Xiang Zhang ◽  
Ji Min Hu ◽  
Chun Ying Shen
Keyword(s):  
Steady State ◽  
Flow Field ◽  
Vortex Structure ◽  
Reynolds Numbers ◽  
Structure Evolution ◽  
Square Cavity ◽  
Large Vortex ◽  
Two Dimensional Flow ◽  
Left And Right ◽  
Secondary Vortices

The transient vortex structure evolution process of two-dimensional flow in a driven square cavity with one moving end was studied. The time curves of flow field variables, the flow patterns of different specific moments and the required times of flow field from static to statistical steady state were comparatively analyzed for different Reynolds numbers. Transient simulating results show that the nascent vortices always appear near the boundaries in the initial driving stage, then gradually move away from the boundaries to form a large vortex almost occupying entire cavity and two secondary vortices in left and right corners of the cavity bottom. The greater the Reynolds numbers, the longer the required times of the flow field reaching by the statistical steady state, also, the more complex of the vortex structure evolution.

A Numerical Study of Unsteady Mixed Convection in a Square Cavity: Transition From Laminar to Turbulent Flow

2013 ◽  
Author(s):  
K. M. Akyuzlu
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Turbulent Flow ◽  
Turbulence Model ◽  
Numerical Study ◽  
Working Fluid ◽  
Heat Transfer Characteristics ◽  
Square Cavity ◽  
Transfer Characteristics ◽  
Unsteady Mixed Convection

A study was conducted to simulate the circulation patterns and heat transfer characteristics of flows in a square cavity during transition from laminar to turbulent mixed convection conditions using numerical techniques. The cavity under study is assumed to be filled with a compressible fluid. The bottom of the cavity is insulated and stationary where as the top of the cavity (the lid) is assumed to be stationary initially and then pulled at constant speed for times greater than zero. The vertical walls of the cavity are kept at constant but unequal temperatures. A two-dimensional, physics based mathematical model is adopted to predict the momentum and heat transfer inside this rectangular cavity. A standard two equation turbulence model is used to model the turbulent flow inside the enclosure and the compressibility of the working fluid is represented by an ideal gas relation. The numerical solution techniques adopted in this study is a hybrid one (implicit-explicit) where the conservation equations for the velocity, temperature, and pressure are solved using an implicit technique (Coupled Modified Strongly Implicit Procedure -CMSIP) whereas the equations for the standard K-ε turbulence model are solved using an explicit (MacCormack) technique. In both techniques, a second order accurate finite difference technique is used to discretize the governing equations. Then numerical experiments were carried out to simulate the unsteady flow and heat transfer characteristics of mixed convection flow inside a square cavity filled with air (Pr = 0.72) for different Richardson numbers in the range of 0.00868–0.03470; corresponding to Reynolds numbers ranging from 2000 to 4000, respectively, when the Rayleigh number was kept constant at 105. Vertical and horizontal temperature and velocity profiles were generated while the flow goes through transition from laminar to turbulent. Changes in wall heat flux were calculated and average Nusselt numbers were determined for each parametric study.

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