Numerical Investigation of Slip Flows Through 2-D U-Shaped Microchannels

2016 ◽  
Author(s):  
Mostafa Shojaeian ◽  
Ali Koşar
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Slip Length ◽  
Slip Flow ◽  
Flow Characteristics ◽  
Slip Condition ◽  
Ansys Fluent ◽  
Micro Electro Mechanical Systems ◽  
Slip Flows ◽  
Solid Liquid Interface

Micro-electro-mechanical systems (MEMS) offer vast applications and those involving fluid flow/gas flows typically operate in the slip flow regime, where the normal non-slip condition assumptions for boundary conditions are not valid. In this study, two-dimensional numerical simulations of continuum and slip flows for U-shaped microchannels were performed to evaluate flow characteristics by means of the ANSYS-FLUENT software. In order to model slip condition existing at the solid-liquid interface of microchannels, a user defined subroutine was linked to the software. The effect of Reynolds number and geometric parameters such as the bend shape and the distance between legs on fluid flow and heat transfer characteristics were examined in detail. The computational results showed that increasing either the slip length or Reynolds number decreased the average friction factor, while the distance between legs does not have any effect on it. Moreover, it was found that the averaged Nusselt number would increase with Reynolds number and the slip length, but increasing the distance between legs decreased the averaged Nu for square bend compared to its negligible increase for circular bend.

Fluid Flow Characteristics of a Confined Slot Jet Without or With a Target Surface

2005 ◽  
Author(s):  
L. K. Liu ◽  
C. J. Fang ◽  
M. C. Wu ◽  
C. Y. Lee ◽  
Y. H. Hung
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Fluid Velocity ◽  
Flow Characteristics ◽  
Target Surface ◽  
Streamwise Velocity ◽  
Separation Distance ◽  
Experimental Investigations ◽  
Flow Parameters ◽  
Fluid Flow Characteristics

A series of experimental investigations with a stringent measurement method on the fluid flow characteristics of slot jet without or with a target surface have been successfully conducted. From all the fluid velocity data measured in the present study, the experimental conditions have been verified to be spanwise-symmetrically maintained and the results have been achieved in a spanwise-symmetric form. Three types of jet configuration without or with target surface are investigated: (A) Confined Slot Jet without Target Surfaces – the fluid flow parameters studied in the present investigation is the jet Reynolds number (ReD). Its ranges are ReD=506-1517. (B) Confined Slot Jet with Smooth Surfaces – the fluid flow parameters studied in the present investigation include the ratio of jet separation distance (H) to nozzle width (W) and the jet Reynolds number (ReD). The ranges of the relevant parameters are H/W=2–10 and ReD=504–1526. (C) Confined Slot Jet with Extended Surfaces – the fluid flow parameters studied include the ratio of jet separation distance (H) to nozzle width (W), the Reynolds number (ReD) and the ratio of extended surface height (Hes) to nozzle width (W). Their ranges are H/W=3–10, Hes/W=0.74-3.40 and ReD=501–1547. The flow characteristics such as the local mean streamwise velocity distribution, mean streamwise velocity decay along jet centerline, local jet turbulence intensity distribution, and turbulence intensities along jet centerline have been presented and discussed in the study.

Analysis of heat transfer and fluid flow of a slot jet impinging on a confined concave surface with various curvature and small jet to target spacing

2019 ◽  
Vol 29 (8) ◽  
pp. 2885-2910 ◽  
Author(s):  
Dandan Qiu ◽  
Lei Luo ◽  
Songtao Wang ◽  
Bengt Ake Sunden ◽  
Xinhong Zhang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Thermal Performance ◽  
Flow Characteristics ◽  
Target Surface ◽  
Surface Curvature ◽  
Content Type ◽  
Curvature Effects ◽  
Target Spacing

Purpose This study aims to focus on the surface curvature, jet to target spacing and jet Reynolds number effects on the heat transfer and fluid flow characteristics of a slot jet impinging on a confined concave target surface at constant jet to target spacing. Design/methodology/approach Numerical simulations are used in this research. Jet to target spacing, H/B is varying from 1.0 to 2.2, B is the slot width. The jet Reynolds number, Rej, varies from 8,000 to 40,000, and the surface curvature, R2/B, varies from 4 to 20. Results of the target surface heat transfer, flow parameters and fluid flow in the concave channel are performed. Findings It is found that an obvious backflow occurs near the upper wall. Both the local and averaged Nusselt numbers considered in the defined region respond positively to the Rej. The surface curvature plays a positive role in increasing the averaged Nusselt number for smaller surface curvature (4-15) but affects little as the surface curvature is large enough (> 15). The thermal performance is larger for smaller surface curvature and changes little as the surface curvature is larger than 15. The jet to target spacing shows a negative effect in heat transfer enhancement and thermal performance. Originality/value The surface curvature effects are conducted by verifying the concave surface with constant jet size. The flow characteristics are first obtained for the confined impingement cases. Then confined and unconfined slot jet impingements are compared. An ineffective point for surface curvature effects on heat transfer and thermal performance is obtained.

scholarly journals HEAT TRANSFER AND FLUID FLOW INSIDE DUCT WITH USING FAN-SHAPE RIBS

2021 ◽  
pp. 1-7
Author(s):  
Ahmed Yousif
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Ansys Fluent ◽  
Flow And Heat Transfer ◽  
Pitch Ratio ◽  
Flow Through ◽  
Energy Equations ◽  
Heat Transfers ◽  
Meshing Process

A 2-D computational analysis is carried out to calculate heat transfer and friction factor for laminar flow through a rectangular duct with using fan–shape ribs as a turbulator. The types of rib shapes are imported on the heat transfer rate and fluid flow in heat exchangers. The present study makes use of fan-shaped ribs with two arrangements. The first arrangement was downstream fan–shape ribs (case 1) and upstream fan–shape ribs (case 2) is investigated. A commercial finite volume package ANSYS FLUENT 16.1 is used for solving the meshing process with continuity, momentum, and energy equations respectively to investigate fluid flow and heat transfer across the ribs surface. The Reynolds number (Re) range of (400 – 2250) with different relative roughness pitch (p/H= 0.17, 0.22, 0.27 and 0.32) at constant rib high (e/H). The results show that the heat transfers and friction increase with using ribs also, the results show that heat transfer Directly proportional to pitch ratio and Reynolds number. The Nusselt number enhancement by (12% -29%).    

scholarly journals Aerodynamic Flow Visualisation Over Surfaces Using Smoke Separation Method from Ansys Fluent

2020 ◽  
Vol 5 (7) ◽  
pp. 32-35
Author(s):  
Virendra Talele ◽  
Niranjan Sonawane ◽  
Omkar Chavan ◽  
Akash Divate ◽  
Niraj Badhe ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
High Reynolds Number ◽  
Turbulence Modeling ◽  
Tracking System ◽  
Adverse Pressure Gradient ◽  
Point Particle ◽  
Flow Visualisation ◽  
Ansys Fluent ◽  
High Reynolds

In the present study, three workbench problem for turbulence modeling with high Reynolds number is used to determine the behavior of fluid flow around the surfaces. The cases for simulation is developed using Ansys workbench CFD fluent module. The computational results are obtained using solution sets of high Reynolds number with the LagrangianEulerian (LE) approach of point particle tracking system in Nevers stoke RANS Equation. The effect of flow pattern around the surface and its kinetic behavior of fluid is evaluated in post-process method of results. By observation, it has been tabulated that fluid flow separation is arousal at the corner end of all surfaces which happens due to evoking of a large adverse pressure gradient.

Numerical Simulation of Flow in a Wavy Wall Microchannel Using Immersed Boundary Method

2020 ◽  
Vol 13 (2) ◽  
pp. 118-125
Author(s):  
Mithun Kanchan ◽  
Ranjith Maniyeri
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Immersed Boundary Method ◽  
Stokes Equations ◽  
Flow Characteristics ◽  
Immersed Boundary ◽  
Solid Boundary ◽  
Wavy Wall ◽  
Dirac Delta ◽  
Boundary Method

Background: Fluid flow in microchannels is restricted to low Reynolds number regimes and hence inducing chaotic mixing in such devices is a major challenge. Over the years, the Immersed Boundary Method (IBM) has proved its ability in handling complex fluid-structure interaction problems. Objectives: Inspired by recent patents in microchannel mixing devices, we study passive mixing effects by performing two-dimensional numerical simulations of wavy wall in channel flow using IBM. Methods: The continuity and Navier-Stokes equations governing the flow are solved by fractional step based finite volume method on a staggered Cartesian grid system. Fluid variables are described by Eulerian coordinates and solid boundary by Lagrangian coordinates. A four-point Dirac delta function is used to couple both the coordinate variables. A momentum forcing term is added to the governing equation in order to impose the no-slip boundary condition between the wavy wall and fluid interface. Results: Parametric study is carried out to analyze the fluid flow characteristics by varying amplitude and wavelength of wavy wall configurations for different Reynolds number. Conclusion: Configurations of wavy wall microchannels having a higher amplitude and lower wavelengths show optimum results for mixing applications.

Fluid Flow Characteristics Around a Pair of Diamond-Shaped Cylinders in Side-by-Side and Tandem Arrangements

2011 ◽  
Author(s):  
Shuichi Torii ◽  
Noritugu Ueda ◽  
Zijie Lin
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Stokes Equations ◽  
Flow Characteristics ◽  
Time History ◽  
Flow Patterns ◽  
Separation Distance ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Gap Spacing

The present study deals with unsteady laminar fluid flow phenomena around a pair of diamond-shaped cylinders in free stream. Emphasis is placed on the effects of the Reynolds number, Re, and the ratio of cylinder separation distance to length of diamond-shaped cylinder, s/d, on the flow patterns in side-by-side and tandem arrangements. The Navier-Stokes equations are discretized using finite difference method to determine the time history of velocity vector in the flow field. The Reynolds numbers, Re, is ranged from 30 to 300 and gap spacing, s/d, is varied from 0.0 to 2.5 for side-by-side and 0.0 to 5.0 for tandem, respectively. The results are compared with the experimental results with the aid of flow visualization method. The study discloses that (i) the generations of Karman vortex streets behind the diamond-shaped cylinders are intensified with an increase in the Reynolds number, (ii) the categorized flow patterns in the wake region of the diamond-shaped islands are affected by s/d, and (iii) the vortex shedding frequency in the wake of diamond-shaped cylinders depends on both the gap spacing and the formation of the vortices.

scholarly journals Augmentation of Nanofluids Heat Transfer in a Circular Pipe with Coiled Tube Insert as Heat Source and Swirl Generator

2019 ◽  
Vol 7 (4.14) ◽  
pp. 365
Author(s):  
S. D. Salman ◽  
. .
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Characteristics ◽  
Vortex Generator ◽  
Ansys Fluent ◽  
Coiled Tube ◽  
Swirl Generator ◽  
Momentum And Heat Transfer ◽  
Fluid Flow Characteristics ◽  
Steady State Heat Transfer

This research present steady state heat transfer and fluid flow characteristics in concentric pipe with coiled tube insert for turbulent flow regime with metal oxide nanofluid using ANSYS-FLUENT 18.0 where the governing equations of mass, momentum and heat transfer were solved simultaneously, using the k-e two equations turbulence model. Copper was chosen as the as metal for the construction of pipe and the helical tube insert. Coiled tube with curvature to pitch ratio as 1 and 2.5 mm in diameter with 1% volume fractions of TiO2 and CuO Nanofluid with Reynolds number ranged from 4000-16000 were considered in this research. The heat generated from constant water temperature (80 °C) with constant flow rates in helical coil (Re=4000). The Result shows that the heat and friction coefficients conducted by vortex generator raised with Reynolds number and accretion of nanoparticle presence. Furthermore, the maximum rate of heat transfer with significant intension in friction coefficient has been produced TiO2 nanofluid by as compared with CuO and water.  

CFD Analysis of Flow and Performance Characteristics of a 90°curved Rectangular Diffuser: Effects of Aspect Ratio and Reynolds Number

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Rakesh Kumaraswamy ◽  
Karthikeyan Natarajan ◽  
R. B. Anand
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Aspect Ratio ◽  
Static Pressure ◽  
Performance Characteristics ◽  
Centrifugal Forces ◽  
Flow Uniformity ◽  
Ansys Fluent ◽  
Concave Wall ◽  
And Performance

Abstract The effect of aspect ratio (AS = 0.5, 1.0, 2.0) and Reynolds number (Re = 1, 2, 4, 8 × 105) on the flow and performance characteristics of a 90° curved rectangular diffuser was examined with the aid of the commercial CFD code ANSYS FLUENT. The results from computational analysis revealed the presence of stream vorticity indicative of secondary flow brought about by the curvature of the diffusing duct. As the fluid flow developed, the inertial core flow was pushed to the outer concave wall by overbearing centrifugal forces. The fluid flow sustained marginal changes with increasing aspect ratio and Reynolds number. However, the flow uniformity at the exit was enhanced. The rise in coefficient of static pressure (Cp) recovery and the drop in coefficient of total pressure loss (Closs) with increasing Reynolds number suggested improved diffuser performance. The flow uniformity index was found to be the highest for the diffuser of aspect ratio 1.

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