Numerical Assessment of Turbulent Flow Driving in a Two-Sided Lid-Driven Cavity with Antiparallel Wall Motion

2021 ◽  
Vol 406 ◽  
pp. 133-148
Author(s):  
El Amin Azzouz ◽  
Samir Houat ◽  
Ahmed Zineddine Dellil
Keyword(s):  
Flow Characteristics ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Systematic Evaluation ◽  
Driven Cavity ◽  
Rans Turbulence Models ◽  
Calculation Results ◽  
Two Dimensional Flow ◽  
Rsm Model ◽  
Secondary Vortices

In this paper, the case of the steady two-dimensional flow in a two-sided lid-driven square cavity is numerically investigated by the finite volume method (FVM). The flow motion is due to the top and bottom horizontal walls sliding symmetrically in the opposite direction with equal velocities, UT and UB, obtained through three respective Reynolds numbers, Re1,2=10000, 15000, and 20000. Due to the lack of availability of experimental results in this Reynolds number margin for this type of flow, the problem is first examined by considering that the flow is turbulent with the inclusion of four commonly used RANS turbulence models: Omega RSM, SST k-ω, RNG k-ε and Spalart-Allmaras (SA). Next, the regime is considered being laminar in the same range of Reynolds numbers. A systematic evaluation of the flow characteristics is performed in terms of stream-function contour, velocity profiles, and secondary vortices depth. Examination of the calculation results reveals the existence of a great similarity of the predicted flow structures between the Omega RSM model and those from the laminar flow assumption. On the other hand, the computed flow with the SST k-ω model, the RNG k-ε model, and the SA model reveals a remarkable under-prediction which appears clearly in the size and number of secondary vortices in the near-wall regions. Various benchmarking results are presented in this study.

scholarly journals Simulation of Lid-Driven Cavity Flow with Internal Circular Obstacles

2020 ◽  
Vol 10 (13) ◽  
pp. 4583 ◽  
Author(s):  
Tingting Huang ◽  
Hee-Chang Lim
Keyword(s):  
Reynolds Number ◽  
Solid Wall ◽  
Vortex Formation ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Time Model ◽  
Cross Sectional ◽  
Driven Cavity ◽  
Secondary Vortices ◽  
Boltzmann Method

The Lattice Boltzmann method (LBM) has been applied for the simulation of lid-driven flows inside cavities with internal two-dimensional circular obstacles of various diameters under Reynolds numbers ranging from 100 to 5000. With the LBM, a simplified square cross-sectional cavity was used and a single relaxation time model was employed to simulate complex fluid flow around the obstacles inside the cavity. In order to made better convergence, well-posed boundary conditions should be defined in the domain, such as no-slip conditions on the side and bottom solid-wall surfaces as well as the surface of obstacles and uniform horizontal velocity at the top of the cavity. This study focused on the flow inside a square cavity with internal obstacles with the objective of observing the effect of the Reynolds number and size of the internal obstacles on the flow characteristics and primary/secondary vortex formation. The current LBM has been successfully used to precisely simulate and visualize the primary and secondary vortices inside the cavity. In order to validate the results of this study, the results were compared with existing data. In the case of a cavity without any obstacles, as the Reynolds number increases, the primary vortices move toward the center of the cavity, and the secondary vortices at the bottom corners increase in size. In the case of the cavity with internal obstacles, as the Reynolds number increases, the secondary vortices close to the internal obstacle become smaller owing to the strong primary vortices. In contrast, depending on the sizes of the obstacles ( R / L = 1/16, 1/6, 1/4, and 2/5), secondary vortices are induced at each corner of the cavity and remain stationary, but the secondary vortices close to the top of the obstacle become larger as the size of the obstacle increases.

Determination of Flow Characteristics and Turbulent Heat Transfer in a Ribbed Roughened Square Duct, Part 2: Numerical Simulations

2011 ◽  
Vol 110-116 ◽  
pp. 2364-2369
Author(s):  
Amin Etminan ◽  
H. Jafarizadeh ◽  
M. Moosavi ◽  
K. Akramian
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Square Duct ◽  
Optimized Model ◽  
Rsm Model

In the part 1 of this research, some useful turbulence models presented. In that part advantages of those turbulence models has been gathered. In the next, numerical details and procedure of solution are presented in details. By use of different turbulence models, it has been found that Spallart-Allmaras predicted the lowest value of heat transfer coefficient; in contrast, RSM1 has projected the more considerable results compared with other models; besides, it has been proven that the two-equation models prominently taken lesser time than RSM model. Eventually, the RNG2 model has been introduced as the optimized model of this research; moreover.

Fluid Flow Analysis in a Pebble Bed Modular Reactor Using RANS Turbulence Models

2008 ◽  
Author(s):  
Margaret Mkhosi ◽  
Richard Denning ◽  
Audeen Fentiman
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Turbulence Intensity ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Pebble Bed ◽  
Rans Turbulence Models ◽  
Flow Domain

The computational fluid dynamics code FLUENT has been used to analyze turbulent fluid flow over pebbles in a pebble bed modular reactor. The objective of the analysis is to evaluate the capability of the various RANS turbulence models to predict mean velocities, turbulent kinetic energy, and turbulence intensity inside the bed. The code was run using three RANS turbulence models: standard k-ε, standard k-ω and the Reynolds stress turbulence models at turbulent Reynolds numbers, corresponding to normal operation of the reactor. For the k-ε turbulence model, the analyses were performed at a range of Reynolds numbers between 1300 and 22 000 based on the approach velocity and the sphere diameter of 6 cm. Predictions of the mean velocities, turbulent kinetic energy, and turbulence intensity for the three models are compared at the Reynolds number of 5500 for all the RANS models analyzed. A unit-cell approach is used and the fluid flow domain consists of three unit cells. The packing of the pebbles is an orthorhombic arrangement consisting of seven layers of pebbles with the mean flow parallel to the z-axis. For each Reynolds number analyzed, the velocity is observed to accelerate to twice the inlet velocity within the pebble bed. From the velocity contours, it can be seen that the flow appears to have reached an asymptotic behavior by the end of the first unit cell. The velocity vectors for the standard k-ε and the Reynolds stress model show similar patterns for the Reynolds number analyzed. For the standard k-ω, the vectors are different from the other two. Secondary flow structures are observed for the standard k-ω after the flow passes through the gap between spheres. This feature is not observable in the case of both the standard k-ε and the RSM. Analysis of the turbulent kinetic energy contours shows that there is higher turbulence kinetic energy near the inlet than inside the bed. As the Reynolds number increases, kinetic energy inside the bed increases. The turbulent kinetic energy values obtained for the standard k-ε and the RSM are similar, showing maximum turbulence kinetic energy of 7.5 m2·s−2, whereas the standard k-ω shows a maximum of about 20 m2·s−2. Another observation is that the turbulence intensity is spread throughout the flow domain for the k-ε and RSM whereas for the k-ω, the intensity is concentrated at the front of the second sphere. Preliminary analysis performed for the pressure drop using the standard k-ε model for various velocities show that the dependence of pressure on velocity varies as V1.76.

scholarly journals A Nonlineark-εTurbulence Model Applicable to High Pressure Gradient and Large Curvature Flow

2014 ◽  
Vol 2014 ◽  
pp. 1-9
Author(s):  
Xiyao Gu ◽  
Junlian Yin ◽  
Jintao Liu ◽  
Yulin Wu
Keyword(s):  
High Pressure ◽  
Pressure Gradient ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Wall Region ◽  
Reynolds Stresses ◽  
Wall Functions ◽  
Large Curvature ◽  
Rans Turbulence Models ◽  
Calculation Results

Most of the RANS turbulence models solve the Reynolds stress by linear hypothesis with isotropic model. They can not capture all kinds of vortexes in the turbomachineries. In this paper, an improved nonlineark-εturbulence model is proposed, which is modified from the RNGk-εturbulence model and Wilcox'sk-ωturbulence model. The Reynolds stresses are solved by nonlinear methods. The nonlineark-εturbulence model can calculate the near wall region without the use of wall functions. The improved nonlineark-εturbulence model is used to simulate the flow field in a curved rectangular duct. The results based on the improved nonlineark-εturbulence model agree well with the experimental results. The calculation results prove that the nonlineark-εturbulence model is available for high pressure gradient flows and large curvature flows, and it can be used to capture complex vortexes in a turbomachinery.

A Numerical Simulation of Unsteady Lid Driven Cavity Flow With Moving Boundaries Using CMSIP

2020 ◽  
Author(s):  
K. M. Akyuzlu ◽  
A. Antoniou
Keyword(s):  
Reynolds Numbers ◽  
Linearization Method ◽  
Finite Difference Schemes ◽  
Algebraic Equations ◽  
Driven Cavity ◽  
Computational Mesh ◽  
Proposed Model ◽  
Unsteady Characteristics ◽  
Strongly Implicit Procedure ◽  
Secondary Vortices

Abstract A two-dimensional, mathematical model is adopted to investigate the development of circulation patterns for compressible lid driven flows inside a rectangular cavity where the bottom of the cavity is free to move at a specified speed. A time and space dependent transformation is applied to the governing equations to obtain a rigid (non-moving) solution domain. The transformed equations are discretized for a uniform and orthogonal computational mesh using second order in space and first order in time finite difference schemes. The resulting nonlinear equations are then linearized using Newton’s linearization method. Finally, the set of algebraic equations that result from this process are put into a matrix form and solved using the Coupled Modified Strongly Implicit Procedure (CMSIP). Numerical experiments are carried out for various Reynolds numbers to verify the accuracy of the solution algorithm. Then the numerical simulations of lid driven flow inside the cavity is carried out for the unsteady case where the aspect ratio of the cavity is changed from 1 to 1.5 at a constant speed. It is concluded that the proposed model is successful in predicting the unsteady characteristics of the primary vortex and the secondary vortices inside a cavity with moving bottom.

Performance Assessment of Different Turbulence Models for a Dual Jet Flowing Over a Heated Sinusoidal Wavy Surface

2021 ◽  
pp. 1-31
Author(s):  
Tej Pratap Singh ◽  
Anupam Dewan
Keyword(s):  
Heat Transfer ◽  
Flow Characteristics ◽  
Maximum Amplitude ◽  
Turbulence Models ◽  
Wavy Surface ◽  
Heated Plate ◽  
Mixing Processes ◽  
Rans Turbulence Models ◽  
Fluid Flow Characteristics ◽  
Number Of Cycles

Abstract An enhancement in heat transfer is the key objective in any thermal system where an efficient cooling is needed. This requirement becomes more important for turbulent flow. A turbulent dual jet is associated with entrainment and mixing processes in several applications. This paper aims at enhancing the heat transfer rate by utilizing the wavy surface of a heated plate. Heat transfer and flow characteristics are studied using five low-Re RANS turbulence models, namely, Yang and Shih k-ε (YS), Launder and Sharma k-ε (LS), realizable k-ε, renormalization group k-ε (RNG) and shear-stress transport k-ω (SST) models. The amplitude of the wavy surface is varied from 0.1 to 0.8 for the number of cycles fixed to 7. The Reynolds number and offset ratio are set to 15000 and 3, respectively. An isothermal wall condition is used at the wavy wall. An experimental validation has been performed. An enhancement of 55.94% in heat transfer is achieved by the RNG k-ε model. Further, it is noticed that the YS model fails to predict the flow separation as the amplitude of the sinusoidal wavy surface increases. However, the SST model reveals that the flow separates when the amplitude increases beyond 0.6. The thermal-hydraulic performance (THP) is found to increase for the RNG model by approximately 13.9% for the maximum amplitude considered. As the profiles of the bottom walls change, various turbulence models predict different fluid flow characteristics.

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.

Dynamics and stability of the wake behind tandem cylinders sliding along a wall

2013 ◽  
Vol 722 ◽  
pp. 291-316 ◽  
Author(s):  
A. Rao ◽  
M. C. Thompson ◽  
T. Leweke ◽  
K. Hourigan
Keyword(s):  
Three Dimensional ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Two Dimensional ◽  
Feedback Cycle ◽  
Tandem Cylinders ◽  
Two Dimensional Flow ◽  
Shedding Frequency ◽  
Dimensional Instability ◽  
Unsteady Regimes

AbstractThe dynamics and stability of the flow past two cylinders sliding along a wall in a tandem configuration is studied numerically for Reynolds numbers ($\mathit{Re}$) between 20 and 200, and streamwise separation distances between 0.1 and 10 cylinder diameters. For cylinders at close separations, the onset of unsteady two-dimensional flow is delayed to higher $\mathit{Re}$ compared with the case of a single sliding cylinder, while at larger separations, this transition occurs earlier. For Reynolds numbers above the threshold, shedding from both cylinders is periodic and locked. At intermediate separation distances, the wake frequency shifts to the subharmonic of the leading-cylinder shedding frequency, which appears to be due to a feedback cycle, whereby shed leading-cylinder vortices interact strongly with the downstream cylinder to influence subsequent leading-cylinder shedding two cycles later. In addition to the shedding frequency, the drag coefficients for the two cylinders are determined for both the steady and unsteady regimes. The three-dimensional stability of the flow is also investigated. It is found that, when increasing the Reynolds number at intermediate separations, an initial three-dimensional instability develops, which disappears at higher $\mathit{Re}$. The new two-dimensional steady flow again becomes unstable, but with a different three-dimensional instability mode. At very close spacings, when the two cylinders are effectively seen by the flow as a single body, and at very large spacings, when the cylinders form independent wakes, the flow characteristics are similar to those of a single cylinder sliding along a wall.

Comparison of RANS Turbulence Models for Prediction of Film Cooling Performance

2008 ◽  
Author(s):  
Katharine L. Harrison ◽  
David G. Bogard
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Turbulence Models ◽  
Transfer Coefficients ◽  
Rans Turbulence Models ◽  
Adiabatic Effectiveness ◽  
Rsm Model

The realizable k-ε, standard k-ω, and RSM turbulence models were used to simulate flat plate film cooling experiments that are commonly described in literature. Adiabatic effectiveness simulations revealed that using the standard k-ω model resulted in the closest agreement with experimentally determined laterally averaged adiabatic effectiveness, but the worst agreement with centerline adiabatic effectiveness. Conversely, the realizable k-ε model agreed worst with experimental laterally averaged adiabatic effectiveness values and best with centerline values. Use of the anisotropic RSM model was not found to predict more realistic coolant spreading than the other models. Simulations to find heat transfer coefficients without film cooling showed good agreement with correlations for all three models, and the closest agreement resulted from using the realizable k-ε model. Heat transfer coefficient augmentation was also examined for two configurations: unit density ratio with and without upstream heating. Laterally averaged heat transfer coefficient augmentation simulations using all three turbulence models agreed well with experiments. However, the spanwise variation in heat transfer coefficient augmentation in all cases was greater than is typically seen experimentally.

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