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.

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.

An Experimental Study of Natural Convection in a Rectangular Enclosure Using PIV Measurement Techniques

2011 ◽  
Author(s):  
K. M. Akyuzlu ◽  
J. Farkas
Keyword(s):  
Experimental Study ◽  
Natural Convection ◽  
Measurement Techniques ◽  
Flow Patterns ◽  
Working Fluid ◽  
Two Dimensional ◽  
Rectangular Enclosure ◽  
Aspect Ratios ◽  
Circulation Patterns ◽  
Piv Measurement

An experimental study is conducted to determine the circulation patterns inside a rectangular enclosure due to natural convection using a Particle Image Velocimeter (PIV). Experiments were conducted using two different fluids (air and water) and for rectangular enclosures with aspect ratios 0.5 and 1.0. Natural convection in enclosures has been experimentally studied in the past. Many of these studies cited in the literature use some kind of an optical method like interferograms, shadowgraphs, streak photographs, or multi-exposure photographs to visualize the flow patterns in the enclosure. The present study employs a commercial two-dimensional PIV to capture, instantaneously, the circulation patterns inside the test section. The test cavity in the present setup is of rectangular shape, which is 5 inches (127 mm) wide, where the height of the enclosure can be changed to obtain aspect ratios of 0.5 and 1.0. The depth of the rectangular enclosure measures 12 inches (305 mm) to minimize the effect of walls normal to the two dimensional flow patterns that are expected in this type of arrangement. The walls of the cavity are made of Aluminum plates. These plates are kept at constant but different temperatures during the experiments. In the present study, hollow glass sphere particles with 10 microns in diameter were used as seeding for water experiments and fine particles/flakes of ash generated from burned incense were used as seeding in the air experiments. For each working fluid, the experiments were repeated for different aspect ratios and for different wall temperature differences which corresponded to Rayleigh numbers in the range of 106 and 107. Velocity fields were captured at steady state for each experiment using the two-dimensional PIV system. Numerical studies were also carried out using a commercial CFD software. Comparisons of the numerical and experimental results indicate a good match in terms of circulation patterns and velocity magnitudes in the core of the buoyancy driven flow. Discrepancies in measured and predicted values of velocities are more pronounced near to the boundaries of the enclosure. Separate measurements with finer interrogation areas and different PIV setting were required to improve the accuracy of the measurements near the corners (top and bottom) of the enclosure. The results of these measurements are also presented.

scholarly journals GEOMETRICAL EVALUATION OF RECTANGULAR FIN MOUNTED IN LATERAL SURFACE OF LID-DRIVEN CAVITY FORCED CONVECTIVE FLOWS

2019 ◽  
Vol 18 (2) ◽  
pp. 98
Author(s):  
E. D. dos Santos ◽  
P. M. Rodrigues ◽  
L. A. Isoldi ◽  
J. F. Prolo Filho ◽  
L. A. O. Rocha ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Thermal Performance ◽  
Degrees Of Freedom ◽  
Reynolds Numbers ◽  
Cavity Surface ◽  
Square Cavity ◽  
Driven Cavity ◽  
Convective Flows ◽  
Constructal Design ◽  
Volume Method

In this work, it is investigated the geometric effect of rectangular fin inserted in a lid-driven square cavity over thermal performance of laminar, incompressible, steady and forced convective flows. This study is performed by applying Constructal Design to maximize the heat transfer between the fin and the cavity flow. For that, the problem is subjected to two constraints: area of the cavity and area of rectangular fin, and two degrees of freedom: height/length ratio of rectangular fin (H1/L1) and its position in upstream surface of the cavity (S/A1/2). It is considered here some fixed parameters, as the ratio between the fin and cavity areas (ϕ = 0.05), the aspect ratio of the cavity dimensions (H/L = 1.0) and Prandtl number (Pr = 0.71). The fin aspect ratio (H1/L1) was varied for three different placements of the fin at the upstream cavity surface (S/A1/2 = 0.1, 0.5 and 0.9) which represents a lower, intermediate and upper positions of the fin. The effects of the fin geometry over the spatial-averaged Nusselt number ( ) is investigated for three different Reynolds numbers (ReH = 10, 102 and 103). The conservation equations of mass, momentum and energy were numerically solved with the Finite Volume Method. Results showed that both degrees of freedom (H1/L1 and S/A1/2) had a strong influence over , mainly for higher magnitudes of Reynolds number. Moreover, the best thermal performance is reached when the fin is placed near the upper surface of the cavity for an intermediate ratio between height and length of rectangular fin, more precisely when (S/A1/2)o = 0.9 and (H1/L1)oo = 2.0.

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.

scholarly journals Mixed convection flow and heat transfer in a double lid- driven cavity containing a heated square block in the center

2020 ◽  
Vol 330 ◽  
pp. 01010
Author(s):  
Asma Ouahouah ◽  
Seddik Kherroubi ◽  
Abderrahmane Bourada ◽  
Nabila Labsi ◽  
Youb Khaled Benkahla
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Thermal Characteristics ◽  
Reynolds Numbers ◽  
Convection Flow ◽  
Square Cavity ◽  
Driven Cavity ◽  
Flow And Heat Transfer ◽  
Laminar Mixed Convection ◽  
Vertical Walls

In the present work, laminar mixed convection of a Newtonian fluid around a hot obstacle in a square cavity with moving vertical walls is studied numerically. The objective of this study is to analyze the effect of the Richardson number (0 ≼ Ri ≼ 10) and Reynolds number (50 ≼ Re ≼ 500) on both hydrodynamic and thermal characteristics around a hot obstacle in the enclosure. The analysis of the obtained results shows that the heat transfer is enhanced for high values of Richardson and Reynolds numbers.

A Study of Unsteady Mixed Convection in a Lid Driven Flow Inside a Rectangular Cavity

2010 ◽  
Author(s):  
K. M. Akyuzlu ◽  
K. Hallenbeck
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Second Order ◽  
Rectangular Cavity ◽  
Constant Speed ◽  
Working Fluid ◽  
Two Dimensional ◽  
Driven Cavity ◽  
Circulation Patterns ◽  
Vertical Walls

A numerical study is conducted to identify the unsteady characteristics of momentum and heat transfer in lid-driven cavity flows. The cavity under study is filled with a compressible fluid and is of rectangular shape. The bottom of the cavity is insulated and stationary where as the top of the cavity (the lid) is pulled at constant speed. The vertical walls of the cavity are kept at constant but unequal temperatures. A two-dimensional, mathematical model is adopted to investigate the shear and buoyancy driven circulation patterns inside this rectangular cavity. This physics based mathematical model consists of conservation of mass, momentum (two-dimensional, unsteady Navier-Stokes equations for compressible flows) and energy equations for the enclosed fluid subjected to appropriate boundary and initial conditions. The compressibility of the working fluid is represented by an ideal gas relation and its thermodynamic and transport properties are assumed to be function of temperature. The governing equations are discretized using second order accurate central differencing for spatial derivatives and second order finite differencing (based on Taylor expansion) for the time derivatives. The resulting nonlinear equations are then linearized using Newton’s linearization method. The set of algebraic equations that result from this process are then put into a matrix form and solved using a Coupled Modified Strongly Implicit Procedure (CMSIP) for the unknowns of the problem. Grid independence and time convergence studies were carried out to determine the accuracy of the square mesh adopted for the present study. Two benchmark cases (driven cavity and rectangular channel flows) were studied to verify the accuracy of the CMSIP. Numerical experiments were then carried out to simulate the unsteady development of the shear and buoyancy driven circulation patterns for different Richardson numbers in the range of 0.036<Ri<100 where the Re number is kept less than 2000 to assure laminar flow conditions inside the cavity. Simulations start with a stagnant fluid subjected to a sudden increase in one of the walls temperature. At the same time the upper lid of the cavity is accelerated, instantaneously, to a constant speed. The circulation patterns, temperature contours, vertical and horizontal velocity profiles were generated at different times of the simulation, and wall heat fluxes and Nusselt numbers were calculated for the steady state conditions. Only the results for a square cavity are presented in this paper. These results indicate that the heat transfer rates at the vertical walls of the cavity are enhanced with the decrease in Richardson number.

Numerical analysis and explore of asymmetrical fluid flow in a two-sided lid-driven cavity

2020 ◽  
Vol 14 (3) ◽  
pp. 7269-7281
Author(s):  
El Amin Azzouz ◽  
Samir Houat
Keyword(s):  
Velocity Ratio ◽  
Two Dimensional ◽  
Lower Side ◽  
Square Cavity ◽  
Driven Cavity ◽  
Parallel Motion ◽  
Bottom Cavity ◽  
Secondary Vortices ◽  
Volume Method ◽  
Fluid Characteristics

The two-dimensional asymmetrical flow in a two-sided lid-driven square cavity is numerically analyzed by the finite volume method (FVM). The top and bottom walls slide in parallel and antiparallel motions with various velocity ratio (UT/Ub=λ) where |λ|=2, 4, 8, and 10. In this study, the Reynolds number Re1 = 200, 400, 800 and 1000 is applied for the upper side and Re2 = 100 constant on the lower side. The numerical results are presented in terms of streamlines, vorticity contours and velocity profiles. These results reveal the effect of varying the velocity ratio and consequently the Reynolds ratio on the flow behaviour and fluid characteristics inside the cavity. Unlike conventional symmetrical driven flows, asymmetrical flow patterns and velocity distributions distinct the bulk of the cavity with the rising Reynolds ratio. For λ>2, in addition to the main vortex, the parallel motion of the walls induces two secondary vortices near the bottom cavity corners. however, the antiparallel motion generates two secondary vortices on the bottom right corner. The parallel flow proves affected considerably compared to the antiparallel flow.

The two-sided lid-driven cavity: experiments on stationary and time-dependent flows

2002 ◽  
Vol 450 ◽  
pp. 67-95 ◽  
Author(s):  
CH. BLOHM ◽  
H. C. KUHLMANN
Keyword(s):  
Three Dimensional ◽  
Standing Waves ◽  
Reynolds Numbers ◽  
Time Dependent ◽  
Flow State ◽  
Incompressible Fluid Flow ◽  
Velocity Measurements ◽  
Driven Cavity ◽  
Rectangular Container ◽  
Hot Film

The incompressible fluid flow in a rectangular container driven by two facing sidewalls which move steadily in anti-parallel directions is investigated experimentally for Reynolds numbers up to 1200. The moving sidewalls are realized by two rotating cylinders of large radii tightly closing the cavity. The distance between the moving walls relative to the height of the cavity (aspect ratio) is Γ = 1.96. Laser-Doppler and hot-film techniques are employed to measure steady and time-dependent vortex flows. Beyond a first threshold robust, steady, three-dimensional cells bifurcate supercritically out of the basic flow state. Through a further instability the cellular flow becomes unstable to oscillations in the form of standing waves with the same wavelength as the underlying cellular flow. If both sidewalls move with the same velocity (symmetrical driving), the oscillatory instability is found to be tricritical. The dependence on two sidewall Reynolds numbers of the ranges of existence of steady and oscillatory cellular flows is explored. Flow symmetries and quantitative velocity measurements are presented for representative cases.

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