Oscillatory Flow Induced Developing Convection in a Shallow Enclosure: Effect of Sinusoidal Bottom Wall Temperature

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Saeid R. Angeneh ◽  
Murat K. Aktas
Keyword(s):  
Heat Transfer ◽  
Oscillatory Flow ◽  
Stokes Equations ◽  
Control Volume ◽  
Acoustic Streaming ◽  
Fluid Motion ◽  
Side Wall ◽  
Convective Transport ◽  
Bottom Wall ◽  
Mean Flow

Abstract The influence of hydrodynamically developing nonzero mean acoustic streaming motion on transient convective heat transfer in an air-filled rectangular enclosure is studied numerically. The enclosure is two-dimensional with sinusoidal bottom wall spatial temperature distribution. The oscillatory flow under relatively large Womersley number regime conditions is actuated by the periodic vibrations of the enclosure side wall. The side walls of the enclosure are adiabatic, while the top wall is isothermal. The compressible form of the Navier–Stokes equations is considered to predict the oscillatory- and time-averaged mean flow fields. A control-volume method based explicit computational scheme is used to simulate the convective transport in the enclosure. The longitudinal and the transverse temperature gradients strongly affect the flow structure in the enclosure. The mean fluid motion alters the heat transfer behavior compared to the pure conduction.

Thermal Convection in an Enclosure With Sinusoidal Bottom Wall Temperature: Effect of Vibrating Side Wall

2012 ◽  
Author(s):  
Murat K. Aktas
Keyword(s):  
Wall Temperature ◽  
Stokes Equations ◽  
Control Volume ◽  
Fluid Motion ◽  
Side Wall ◽  
Convective Transport ◽  
Bottom Wall ◽  
Navier Stokes ◽  
Test Case ◽  
Mean Flow

The effects of a vibrating side wall on flow structure and heat transport in an air-filled two dimensional rectangular shallow enclosure with sinusoidal spatial bottom wall temperature distribution is studied numerically. The vibrating side wall induces an oscillating flow having nonzero mean component in the enclosure. The side walls of the enclosure are adiabatic. The top wall is isothermal and kept at initial temperature. The fully compressible form of the Navier–Stokes equations are considered to predict the oscillatory and time averaged mean flow fields. A control-volume method based, explicit computational scheme is used to simulate the convective transport in the enclosure. The simulation results of a test case for an unheated enclosure are compared with the existing literature for code validation. The sinusoidal temperature gradient of the bottom wall strongly affects the flow structures and velocities. The mean fluid motion significantly alters the overall heat transfer from the bottom wall.

Heat Transfer Enhancement by Irregular Acoustic Streaming in a Shallow Enclosure

2009 ◽  
Author(s):  
Murat K. Aktas ◽  
Turkuler Ozgumus
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Acoustic Streaming ◽  
Fluid Motion ◽  
Bottom Wall ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Left Wall ◽  
Time Marching ◽  
Transverse Temperature

The effects of classical and irregular acoustic streaming structures on convective heat transport in air-filled two dimensional rectangular enclosures are investigated numerically. The oscillatory fluid motion and the resulting streaming motion are driven by cyclic vibration of the enclosure left wall. The fully compressible form of the Navier – Stokes equations are employed to model the transport phenomenon in the enclosure. An explicit time-marching Flux-Corrected Transport (FCT) Algorithm is used to simulate the oscillatory flow field, streaming patterns and associated thermal convection in the enclosure. The vertical walls of enclosure are thermally insulated. The bottom wall is heated isothermally while the top wall is kept at the initial temperature. The transverse temperature gradients strongly affect the acoustic streaming velocities and structures. The irregular streaming significantly augments the heat transfer from the enclosure bottom wall.

Heat Transfer Enhancement by Acoustic Streaming in an Enclosure

2005 ◽  
Vol 127 (12) ◽  
pp. 1313-1321 ◽  
Author(s):  
Murat K. Aktas ◽  
Bakhtier Farouk ◽  
Yiqiang Lin
Keyword(s):  
Heat Transfer ◽  
Acoustic Waves ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Acoustic Streaming ◽  
Standing Waves ◽  
Side Wall ◽  
Temperature Fields ◽  
Vertical Side ◽  
Acoustic Standing Wave

Thermal convection in a differentially heated shallow enclosure due to acoustic excitations induced by the vibration of a vertical side wall is investigated numerically. The fully compressible form of the Navier-Stokes equations is considered and an explicit time-marching algorithm is used to track the acoustic waves. Numerical solutions are obtained by employing a highly accurate flux corrected transport algorithm. The frequency of the wall vibration is chosen such that an acoustic standing wave forms in the enclosure. The interaction of the acoustic standing waves and the fluid properties trigger steady secondary streaming flows in the enclosure. Simulations were also carried out for “off-design” vibration frequency where no standing waves were formed. The effects of steady second order acoustic streaming structures are found to be more significant than the main oscillatory flow field on the heat transfer rates. The model developed can be used for the analysis of flow and temperature fields driven by acoustic transducers and in the design of high performance resonators for acoustic compressors.

Micro Cooling Based on Acoustic Streaming

2008 ◽  
Author(s):  
Hongming Sun ◽  
Hang Guo
Keyword(s):  
Heat Transfer ◽  
Analytical Study ◽  
Stokes Equations ◽  
Acoustic Radiation ◽  
Acoustic Streaming ◽  
Fluid Motion ◽  
Radiation Force ◽  
Cooling Effect ◽  
Navier Stokes ◽  
Navier Stokes Equations

Heat transfer due to forced convection caused by acoustic streaming in microfluidic devices is shown to have potential in cooling effect. However, few studies are made for theoretically studying the fluid motion induced by the acoustic field and forced heat transfer for micro cooling in microdevices. In this paper, Navier-Stokes equations are first employed to study acoustic radiation force and acoustic streaming in microchannel actuated by ultrasonic vibration. Then, an analytical study of fluid motion acoustically induced and the temperature field in microchannel is investigated to determine the enhancement of cooling effect in microchannel with acoustic streaming.

Simulation of Acoustic Streaming in a Resonator

2004 ◽  
Author(s):  
Bakhtier Farouk ◽  
Murat K. Aktas
Keyword(s):  
Flow Field ◽  
Standing Wave ◽  
Oscillatory Flow ◽  
Stokes Equations ◽  
Acoustic Streaming ◽  
Flow Patterns ◽  
Vortical Flow ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Streaming Flow

Formation of vortical flow structures in a rectangular enclosure due to acoustic streaming is investigated numerically. The oscillatory flow field in the enclosure is created by the vibration of a vertical side wall of the enclosure. The frequency of the wall vibration is chosen such that a standing wave forms in the enclosure. The interaction of this standing wave with the horizontal solid walls leads to the production of Rayleigh type acoustic streaming flow patterns in the enclosure. All four walls of the enclosure considered are thermally insulated. The fully compressible form of the Navier-Stokes equations is considered and an explicit time-marching algorithm is used to explicitly track the acoustic waves. Numerical solutions are obtained by employing a highly accurate flux corrected transport (FCT) algorithm for the convection terms. A time-splitting technique is used to couple the viscous and diffusion terms of the full Navier-Stokes equations. Non-uniform grid structure is employed in the computations. The simulation of the primary oscillatory flow and the secondary (steady) streaming flows in the enclosure is performed. Streaming flow patterns are obtained by time averaging the primary oscillatory flow velocity distributions. The effect of the amount of wall displacement on the formation of the oscillatory flow field and the streaming structures are studied. Computations indicate that the nonlinearity of the acoustic field increases with increasing amount of the vibration amplitude. The form and the strength of the secondary flow associated with the oscillatory flow field and viscous effects are found to be strongly correlated to the maximum displacement of the vibrating wall. Total number of acoustic streaming cells per wavelength is also determined by the strength and the level of the nonlinearity of the sound field in the resonator.

Heat transfer from a circular cylinder by acoustic streaming

1967 ◽  
Vol 30 (2) ◽  
pp. 337-355 ◽  
Author(s):  
Peter D. Richardson
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Natural Convection ◽  
Circular Cylinder ◽  
Prandtl Number ◽  
Acoustic Streaming ◽  
Mean Flow ◽  
Wide Range ◽  
Transverse Oscillations ◽  
Streaming Flow

An analysis is described for convection from a circular cylinder subjected to transverse oscillations relative to the fluid in which it is immersed. The analysis is based upon use of the acoustic streaming flow field. It is assumed that the frequency involved is sufficiently small that the acoustic wavelength in the fluid is much larger than the cylinder diameter, and that there is no externally imposed mean flow across or along the cylinder. Solutions are presented which are appropriate for a wide range of Prandtl number, and the cases of small and of large streaming Reynolds number are distinguished. The analysis compares favourably with experiments when the influence of natural convection is small.

Heat Transfer Enhancement of a Backward-Facing Step Flow in a Duct by Static and Dynamic Devices

2007 ◽  
Author(s):  
Kyoji Inaoka ◽  
Kouji Kawakami ◽  
Yoshi Nishii ◽  
Mamoru Senda
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Large Scale ◽  
Fluid Motion ◽  
Side Wall ◽  
Transfer Enhancement ◽  
Backward Facing Step ◽  
Electromagnetic Actuators ◽  
Flow Recirculation ◽  
Flow Modification

Flow modification downstream of a backward-facing step has been tried in order to achieve heat transfer enhancement by introducing two kinds of devices, a triangle prism rib and electromagnetic actuators, on the step edge. The triangle rib attached to the side-wall corner makes the downward flow inclined and generates a circulation-like fluid motion behind it. Because both flows work effective in reducing the flow re-circulation caused behind the step, large heat transfer recovery is obtained near the side-wall. This advantage of the triangle rib remains effective when the flap actuations are imposed. Thus, the large-scale unsteady vortex intensively reduces the flow recirculation, the triangle rib with flap actuations attains the largest heat transfer recovery behind the step.

Turbulent Natural Convection in Partitioned Square Cavities with Different Lengths and Positions

2018 ◽  
Vol 877 ◽  
pp. 313-319
Author(s):  
A. Nouri-Borujerdi ◽  
F. Sepahi
Keyword(s):  
Natural Convection ◽  
Turbulent Flow ◽  
Stokes Equations ◽  
Control Volume ◽  
Bottom Wall ◽  
Staggered Grid ◽  
Viscous Effects ◽  
Left Wall ◽  
Turbulent Natural Convection ◽  
Upwind Schemes

The effect of partition on turbulent natural convection has been investigated numerically with different lengths and positions in an air filled square cavity. The top wall of the cavity is assumed to be cold and the other three walls are hot. Two-dimensional governing equations based on Reynolds-averaged Navier-Stokes equations are solved numerically by control volume method in a staggered grid manner. The iterative SIMPLE algorithm is also used to solve the discretized momentum equations to compute the intermediate velocity and pressure fields linked through the momentum equations. The hybrid differencing scheme which is based on a combination of central and upwind schemes is employed to discretize the convective and diffusion terms of the equations respectively. To describe the structure of turbulent flow which is changed due to the increasing importance of viscous effects, wall function was applied to simulate the turbulent flow. The results show that when the partition is placed on the top or bottom wall, the heat transfer rate through the bottom wall increases by increasing the partition length. The number of vortices established in the cavity depends on the partition length. Furthermore, when the partition is mounted on the left or right wall, only a small part of the top wall has a direct interaction with the left wall and the rest of that has an indirect interaction with the bottom wall.

Combined Natural Convection and Volumetric Radiation in a Horizontal Annulus: Spectral and Finite Volume Predictions

1999 ◽  
Vol 121 (3) ◽  
pp. 610-615 ◽  
Author(s):  
D.-C. Kuo ◽  
J. C. Morales ◽  
K. S. Ball
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Stokes Equations ◽  
Control Volume ◽  
Navier Stokes ◽  
Differential Approximation ◽  
Navier Stokes Equations ◽  
Influence Matrix ◽  
Potential Benefits ◽  
The Mathematical Model

Combined natural convection and radiation in a two-dimensional horizontal annulus filled with a radiatively participating gray medium is studied numerically by using a control-volume-based finite difference method and a spectral collocation method coupled with an influence matrix technique. The mathematical model includes the continuity equation, the incompressible Navier-Stokes equations, the energy equation, and the radiative transfer equation (RTE), which is modeled using the P1 differential approximation. Computed results for two Rayleigh numbers, Ra = 104 and Ra = 105, for several combinations of the radiation-conduction parameter, NR, and the optical thickness, τ, are presented. The differences observed in the predicted flow structures and heat transfer characteristics are described. Furthermore, an unusual flow structure is studied in detail, and multiple solutions are found. Finally, the potential benefits of applying spectral methods to problems involving radiative heat transfer are demonstrated.

Theoretical Distributions of Heat Transfer Downstream of a Backstep in Supersonic Turbulent Flow

1972 ◽  
Vol 94 (1) ◽  
pp. 87-94 ◽  
Author(s):  
J. P. Lamb ◽  
C. G. Hood
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Turbulent Flow ◽  
Wall Temperature ◽  
Control Volume ◽  
Convective Transport ◽  
Transport Processes ◽  
Independent Variables ◽  
Test Conditions ◽  
Wide Range

A physically perceptive model is presented for the flow field and convective transport processes in the vicinity of reattachment of a planar, supersonic, turbulent flow. Control volume methods are utilized extensively in the analysis and the restating integral equations are solved by various numerical search techniques. The analysis enables one to determine significant parameters in the flow field as well as the heat transfer distribution and associated wall temperature of the reattachment surface. Also presented is a general correlation of predicted results for the convection process in terms of pertinent independent variables. The correlated results are shown to agree with measurements for a wide range of test conditions.

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