Thermally Developing 3D Cross Flow Between Cross Corrugated Parallel Plates in Evaporative Coolers

2010 ◽  
Author(s):  
Ehsan Tavakoli ◽  
Reza Hosseini
Keyword(s):  
Pressure Drop ◽  
Flow Direction ◽  
Cross Flow ◽  
Navier Stokes ◽  
Parallel Plates ◽  
Main Emphasis ◽  
Saturation Efficiency ◽  
Finite Difference Discretization ◽  
Corrugated Plates ◽  
Energy Equations

The 3D cross flow between parallel corrugated plates with perpendicular directions of corrugation is numerically modeled as a laminar, incompressible, steady flow. The present work tries to investigate the thermally developing characteristics of the flow in this type of geometry, in the case of constant temperature on walls. The main emphasis is on introducing correlations for saturation efficiency and simply modeling the evaporation process within evaporative coolers with such geometries. The applied numerical method is the Chorin’s artificial incompressibility method and finite difference discretization is used to model the Navier-Stokes and energy equations in a structured mesh. The results show that saturation efficiency decreases with increase in Reynolds number. This also depends on the depth of evaporative media along the flow direction. Increasing the number of waves along the flow direction, results higher saturation efficiencies and also more pressure drop. For a specific saturation efficiency, the overall pressure drop decreases at higher amplitude to wavelength ratios. Also the overall pressure drop grows as the depth of the domain increases. The same trend is observed for experimental data of commercial evaporative pads.

VIV and WIV Suppression With Parallel Control Plates on a Pair of Circular Cylinders in Tandem

2009 ◽  
Author(s):  
Gustavo R. S. Assi ◽  
Peter W. Bearman
Keyword(s):  
Circular Cylinder ◽  
Drag Reduction ◽  
Flow Direction ◽  
Cross Flow ◽  
Offshore Structures ◽  
Circular Cylinders ◽  
Parallel Plates ◽  
Tandem Cylinders ◽  
Helical Strakes ◽  
Viv Suppression

Experiments have been carried out on two-dimensional devices fitted to a rigid length of circular cylinder to investigate the efficiency of pivoting parallel plates as wake-induced vibration suppressors. Measurements are presented for a circular cylinder with low mass and damping which is free to respond in the cross-flow direction. It is shown how VIV and WIV can be practically eliminated by using free to rotate parallel plates on a pair of tandem cylinders. Unlike helical strakes, the device achieves VIV suppression with 33% drag reduction when compare to a pair of fixed tandem cylinders at the same Reynolds number. These results prove that suppressors based on parallel plates have great potential to suppress VIV and WIV of offshore structures with considerable drag reduction.

Numerical investigation of vortex-induced vibration of an elastically mounted circular cylinder with One-degree of freedom at high Reynolds number using different turbulent models

2018 ◽  
Vol 233 (2) ◽  
pp. 443-453 ◽  
Author(s):  
Niaz Bahadur Khan ◽  
Zainah Ibrahim
Keyword(s):  
Reynolds Number ◽  
Flow Direction ◽  
Cross Flow ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Flow Around Cylinder ◽  
Reynolds Averaged Navier Stokes ◽  
Turbulent Models

This study presents numerical investigation for flow around cylinder at Reynolds number = 104 using different turbulent models. Numerical simulations have been conducted for fixed cylinder case at Reynolds number = 104 and for cylinder free to oscillate in cross-flow direction, at Reynolds number O (104), mass–damping ratio = 0.011 and range of frequency ratio wt = 0.4–1.4 using two-dimensional Reynolds-averaged Navier–Stokes equations. In the literature, the study has been conducted using detached eddy simulation, large eddy simulation and direct numerical simulation which are comparatively expensive in terms of computational cost. This study utilizes the Reynolds-averaged Navier–Stokes shear stress transport k-ω and realizable k-ε models to investigate the flow around fixed cylinder and flow around cylinder constrained to oscillate in cross-flow direction only. Hydrodynamic coefficients, vortex mode shape and maximum amplitude ( Ay/ D) extracted from this study are compared with detached eddy simulation, large eddy simulation and direct numerical simulation results. Results obtained using two-dimensional Reynolds-averaged Navier–Stokes shear stress transport k-ω model are encouraging, while realizable k-ε model is unable to capture the entire response branches. In addition, broad range of “lock-in” region is observed due to delay in capturing the transition from upper to lower branch during two-dimensional realizable k-ε analyses.

The Study of Combined Electroosmotic and Pressure Driven Flow in Wavy Nanochannels

2010 ◽  
Author(s):  
Naga Siva Kumar Gunda ◽  
Suman Chakraborty ◽  
Sushanta Kumar Mitra
Keyword(s):  
Flow Pattern ◽  
Stokes Equations ◽  
Flow Direction ◽  
Debye Length ◽  
Surface Profile ◽  
Base Flow ◽  
Navier Stokes ◽  
Parallel Plates ◽  
Pressure Driven Flow ◽  
Pressure Driven

Solid surfaces of micro/nanochannels exhibit a certain degree of roughness that is incurred during fabrication and/or adsorption of macromolecules. The presence of such roughness changes the flow pattern in electroosmotic flows (EOF). The present study investigates the effect of surface waviness on combined EOF and pressure driven flow (PDF) of an electrolyte solution, in a nanochannel having charged walls. The surface profile of the top and bottom walls vary either in a varicose or in a sinuous mode. The problem is solved by using the Perturbation model, a modified linearized disturbance Navier-Stokes equations, by assuming two-dimensional combined EOF and PDF between two parallel plates as base flow. By discretizing the linearized disturbance equations using the Chebyshev collocation method in the wall normal direction and Fourier transformation in the flow direction, the perturbed velocity components are calculated. The effects of electric double layer (EDL) and amplitude of wavy surface on the flow pattern are studied. The effects of overlapped EDL are also studied as one of the limiting case. The formation of circulation regions is observed in the varicose mode channel when the EOF and PDF are flowing in the opposite direction. The decrease in the number of circulation regions is ob served for the decrease in the value of average half height of the channel to debye length ratio (κ). Serpentine or triangular type waviness in the streamline velocity is observed in sinuous mode type channel when the EOF and PDF are in opposite directions. The increase in the waviness of the streamline velocity is observed for decrease in the value of κ and increase in the amplitude a when both EOF and PDF are flowing in the same direction.

scholarly journals Why the Coriolis force turns a wind farm wake clockwise in the Northern Hemisphere

2016 ◽  
Author(s):  
Maarten Paul van der Laan ◽  
Niels Nørmark Sørensen
Keyword(s):  
Coriolis Force ◽  
Turbulent Mixing ◽  
Wind Farm ◽  
Flow Direction ◽  
Cross Flow ◽  
Momentum Balance ◽  
Navier Stokes ◽  
Strong Wind ◽  
High Roughness ◽  
Turbine Wake

Abstract. The interaction between the Coriolis force and a wind farm wake is investigated by Reynolds-Averaged Navier-Stokes simulations, using two different wind farm representations: a high roughness and alternatively by 5 × 5 actuator disks. Surprisingly, the calculated wind farm wake deflection is opposite in the two simulations. A momentum balance in the cross flow direction shows that the interaction between the Coriolis force and the 5 × 5 actuator disks is complex due to turbulent mixing of veered momentum from above into the wind farm, which is not observed for the interaction between the Coriolis force and a roughness change. An additional simulation of a single actuator disk, operating in a shallow atmospheric boundary layer, confirms that the Coriolis force indirectly turns a wind turbine wake clockwise, as observed from above, due to the presence of a strong wind veer.

Vortex-Induced Vibration of Two Side-by-Side Cylinders With a Small Gap in Uniform Flow

2017 ◽  
Author(s):  
Adnan Munir ◽  
Ming Zhao ◽  
Helen Wu
Keyword(s):  
Stokes Equations ◽  
Flow Direction ◽  
Three Dimensional ◽  
Cross Flow ◽  
Circular Cylinders ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Gap Ratio ◽  
Vortex Induced Vibrations ◽  
Lock In

Vortex-induced vibrations of two elastically mounted and rigidly coupled circular cylinders in side-by-side arrangement in steady flow are investigated numerically. The vibration of the cylinders is limited to the cross-flow direction only. The three-dimensional Navier-Stokes equations are solved using the Petrov-Galerkin Finite element method and the equation of motion is solved using the fourth order Runge Kutta method. It is well known that when the gap between two stationary side-by-side cylinders is very small, the flow between the two cylinders is biased towards one cylinder and the lift force on each cylinder is significantly smaller than that of an isolated single cylinder. The aim of this study is to investigate the effect of a small gap ratio of 0.5 between the two cylinders on the lock-in regime and the amplitude of the vibration of two side-by-side cylinders in a fluid flow. Simulations are carried out for a constant mass ratio of 2, a constant Reynolds number of 1000 and a range of reduced velocities. It is found that in the lock-in range of the reduced velocity, the two cylinders vibrate about their balance position with high amplitudes. Outside the lock-in regime the flow from the gap becomes biased towards one cylinder, which is similar to that from the gap between stationary cylinders.

Numerical Investigation of the Natural Convection Flows for Low-Prandtl Fluids in Vertical Parallel-Plates Channels

2005 ◽  
Vol 73 (1) ◽  
pp. 96-107 ◽  
Author(s):  
Antonio Campo ◽  
Oronzio Manca ◽  
Biagio Morrone
Keyword(s):  
Natural Convection ◽  
Computational Procedure ◽  
Navier Stokes ◽  
Computational Domain ◽  
Parallel Plates ◽  
Nusselt Numbers ◽  
Aspect Ratios ◽  
Rate Maximum ◽  
Induced Flow ◽  
Energy Equations

Laminar natural convection of metallic fluids (Pr⪡1) between vertical parallel plate channels with isoflux heating is investigated numerically in this work. The full elliptic Navier-Stokes and energy equations have been solved with the combination of the stream function and vorticity method and the finite-volume technique. An enlarged computational domain is employed to take into account the flow and thermal diffusion effects. Results are presented in terms of velocity and temperature profiles. The investigation also focuses on the flow and thermal development inside the channel; the outcomes show that fully developed flow is attained up to Ra=103, whereas the thermal fully developed condition is attained up to Ra=104. Further, correlation equations for the dimensionless induced flow rate, maximum dimensionless wall temperatures, and average Nusselt numbers as functions of the descriptive geometrical and thermal parameters covering the collection of channel Grashof numbers 1.32×103⩽Gr∕A⩽5.0×106 and aspect ratios 5⩽A⩽15. Comparison with experimental measurements has been presented to assess the validity of the numerical computational procedure.

Transient Analysis of Natural Convection in a Horizontal Open Ended Cavity

2002 ◽  
Author(s):  
Assunta Andreozi ◽  
Oronzio Manca ◽  
Yogesh Jaluria
Keyword(s):  
Natural Convection ◽  
Stokes Equations ◽  
Chemical Vapor ◽  
Navier Stokes ◽  
Uniform Heat Flux ◽  
Temperature Profiles ◽  
Two Dimensional ◽  
Parallel Plates ◽  
Penetration Length ◽  
Energy Equations

The configuration of two horizontal parallel walls can be found in many applications, such as the cooling of electronic components, solar energy systems and chemical vapor deposition systems (CVD). In the present investigation a transient numerical analysis for laminar natural convection in air between two horizontal parallel plates, with the upper plate heated at uniform heat flux and the lower one unheated, is carried out by means of the finite volume method. The model was assumed to be two-dimensional. The full two-dimensional Navier-Stokes equations together with the continuity and energy equations are solved by a numerical scheme derived from a SIMPLE-like algorithm in an H-shaped domain. Results are presented in terms of velocity and temperature profiles, wall temperature profiles and the temporal behavior of several significant variables, such as the penetration length, is reported for different Rayleigh numbers and aspect ratio values.

scholarly journals Unsteady Heat Transfer from an Equilateral Triangular Cylinder in the Unconfined Flow Regime

2011 ◽  
Vol 2011 ◽  
pp. 1-13 ◽  
Author(s):  
Amit Dhiman ◽  
Radhe Shyam
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Prandtl Number ◽  
Flow Regime ◽  
Cross Flow ◽  
Navier Stokes ◽  
Central Difference ◽  
Simple Method ◽  
Energy Equations

Effects of Reynolds number on the heat transfer characteristics of a long (heated) equilateral triangular cylinder are investigated for the range of conditions Re = 50–150 (in the steps of 10) and Prandtl number = 0.71 (air) in the unconfined unsteady cross-flow regime. In order to simulate the present situation, the computational grid is created by using commercial grid generator GAMBIT and the numerical computations are carried out by using FLUENT (6.3). The SIMPLE method is used to solve continuity, Navier-Stokes and energy equations along with the appropriate boundary conditions. The second order upwind scheme is used to discretize the convective terms, while the central difference scheme is used to discretize the diffusive terms in the governing equations. The present results are in an excellent agreement with the literature values. The temperature isotherms and temporal history of Nusselt number are presented in detail. The local as well as time-averaged Nusselt numbers are calculated. The time-averaged Nusselt number increases with increasing Reynolds number for the fixed value of the Prandtl number. Finally, the present numerical results are used to develop the simple heat transfer correlation for the range of conditions covered here.

Numerical Investigation of Vortex-Induced Vibration (VIV) of a Circular Cylinder in Oscillatory Flow

2011 ◽  
Author(s):  
Ming Zhao ◽  
Liang Cheng ◽  
Tongming Zhou
Keyword(s):  
Circular Cylinder ◽  
Oscillatory Flow ◽  
Stokes Equations ◽  
Flow Direction ◽  
Cross Flow ◽  
Frequency Component ◽  
Degree Of Freedom ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Vortex Induced Vibration

Vortex-induced vibration (VIV) of a circular cylinder in oscillatory flow is investigated numerically in this study. The incompressible Reynolds-Averaged Navier-Stokes equations governing fluid flow around a circular cylinder are solved using Arbitrary Langrangian-Eulerian (ALE) scheme and Petrov-Galerkin finite element method. The equation of motion is solved for the displacements of the cylinder both in the inline and cross-flow directions. The numerical model is firstly validated against the experimental results of one-degree-of-freedom VIV in cross-flow direction. It is found that both VIV frequency and amplitude vary with reduced velocity for a fixed KC number. In most of the simulated cases the vibration comprises of multiple frequencies of different amplitudes. Each frequency component is multiple times of the frequency of the oscillatory flow. Two-degree-of-freedom VIV is investigated with the same parameters used in the one-degree-of-freedom case. By examining the XY-trajectory of the vibration, it if found that the vibration follows different trajectory for different KC numbers or reduced velocities.

Three-Dimensional Investigation of a Laminar Impinging Square Jet Interaction With Cross-Flow

2003 ◽  
Vol 125 (2) ◽  
pp. 243-249 ◽  
Author(s):  
L. B. Y. Aldabbagh ◽  
I. Sezai ◽  
A. A. Mohamad
Keyword(s):  
Flow Velocity ◽  
Three Dimensional ◽  
Cross Flow ◽  
Jet Impingement ◽  
Horseshoe Vortex ◽  
Navier Stokes ◽  
Complex Nature ◽  
Plate Spacing ◽  
Cross Flow Velocity ◽  
Energy Equations

The flow and heat transfer characteristics of an impinging laminar square jet through cross-flow have been investigated numerically by using the three-dimensional Navier-Stokes and energy equations in steady state. The simulations have been carried out for jet to cross-flow velocity ratios between 0.5 and 10 and for nozzle exit to plate distances between 1D and 6D, where D is the jet width. The complex nature of the flow field featuring a horseshoe vortex has been investigated. The calculated results show that the flow structure is strongly affected by the jet-to-plate distance. In addition, for jet-to-plate spacing of one jet width and for jet to cross-flow velocity ratios less than 2.5 an additional peak occurs at about three-dimensional downstream of the jet impingement point. For high jet to cross-flow ratios two horseshoe vortices form around the jet in the case of small jet-to-plate spacings.

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