Numerical Study of External Flow over Ducts with Various Cross-Sections

2016 ◽  
Vol 366 ◽  
pp. 10-16 ◽  
Author(s):  
Erfan Maleki ◽  
Hani Sadrhosseini
Keyword(s):  
Cross Sections ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
External Flow ◽  
Two Dimensions ◽  
Wake Region ◽  
Reattachment Point ◽  
Cross Sectional ◽  
Low Reynolds Numbers ◽  
Stagnation Points

In this article a comprehensive numerical study is performed to compare the effect of fluid flow across a duct with various cross sectional shapes and with different velocities of the flow. Circular, elliptical and rectangular cross sections have been chosen for the ducts and air flows across them with four values of low Reynolds numbers in the range of Re = 1 to Re = 1000. Continuity and momentum equations with proper boundary conditions are solved in two dimensions. Streamlines, pressure distribution and Velocity profiles are obtained and creation of vortices, boundary layers, separation region, wake region, reattachment point and stagnation points are studied in detail and the results are compared for various cases. The value of the Reynolds number which the flow transits from steady to unsteady has been compared for the different cross sectional shapes.

The LBE Simulation and PIV Experimental Study on a Novel Viscous Pump

2005 ◽  
Author(s):  
Fan Yang ◽  
Shuhong Liu ◽  
Jinwei Li ◽  
Yulin Wu
Keyword(s):  
Boundary Condition ◽  
Unsteady Flow ◽  
Cross Sections ◽  
Lattice Boltzmann ◽  
Moving Boundary ◽  
Flow Problem ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Moving Boundary Condition

A numerical study and PIV investigation of flow in a novel viscous-based pumping device appropriate for microscale applications is described. The device, essentially consisting of a rotating cylinder eccentrically placed in a channel, is shown to be capable of generating a net flow. The two shape cross-sections of cylinders, the circular and four semi-elliptic lobed contour are studied, which is the steady and unsteady flow problem, respectively. The lattice Boltzmann equation (LBE) simulations at low Reynolds numbers are carried out to study the influence of various geometric parameters, which the results are compared with the PIV experiment ones. The unified solid curved wall boundary condition based on interpolation and the balance of momentum on the wall of the LBE simulation is used in steady and unsteady flow, and the moving boundary condition is also used in the latter. The numerical results indicated that the more effective pumping and better performance is obtained with the decrease of Reynolds number, as well as the increase regular degree of cylinder cross-section.

A numerical study on free-fall of a torus with initial inclination angle at low Reynolds numbers

2021 ◽  
Vol 107 ◽  
pp. 103389
Author(s):  
Tao Huang ◽  
Haibo Zhao ◽  
Sai Peng ◽  
Jiayu Li ◽  
Yang Yao ◽  
...  
Keyword(s):  
Inclination Angle ◽  
Numerical Study ◽  
Free Fall ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Low Reynolds

Numerical Study of Winglet at Low Reynolds Numbers

2013 ◽  
Author(s):  
Sina Pooladsanj ◽  
Mehran Tadjfar
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Vortex Flow ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Flow Zone ◽  
Low Reynolds Numbers ◽  
Structured Grid ◽  
Flow Field Characteristics ◽  
Wing Aspect Ratio

A numerical study has been performed to evaluate the aerodynamics coefficients of a winglet in the range of Reynolds numbers below 30,000. In this study some parameters on winglet design have been considered. The effect of winglet-tip airfoil thickness has been investigated on aerodynamics coefficients. In order to explore this effect, two different airfoils (NACA0002 and NACA0012) were employed at the winglet-tip. The influence of varying the winglet connection angle to the wing on aerodynamics coefficients and flow field characteristics in the vortex flow zone such as; circulation magnitude and vorticity magnitude in the vortex core have been studied. Six connection angles including 20°, 30°, 40°, 50°, 60° and 70° have been studied. Negative values of these angles have also been considered. In addition, the effect of changing wing aspect ratio on aerodynamics coefficients has been investigated. To solve the flow field around the studied geometry a fully structured grid was used which consists of 84 blocks.

scholarly journals Numerical and Experimental Study of Cross-Sectional Effects on the Mixing Performance of the Spiral Microfluidics

Micromachines ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1470
Author(s):  
Omid Rouhi ◽  
Sajad Razavi Bazaz ◽  
Hamid Niazmand ◽  
Fateme Mirakhorli ◽  
Sima Mas-hafi ◽  
...  
Keyword(s):  
Cross Sections ◽  
Numerical Study ◽  
Large Angle ◽  
Element Model ◽  
Channel Length ◽  
Cross Sectional ◽  
Flow Rates ◽  
Lab On Chip ◽  
Mixing Performance ◽  
Dean Flow

Mixing at the microscale is of great importance for various applications ranging from biological and chemical synthesis to drug delivery. Among the numerous types of micromixers that have been developed, planar passive spiral micromixers have gained considerable interest due to their ease of fabrication and integration into complex miniaturized systems. However, less attention has been paid to non-planar spiral micromixers with various cross-sections and the effects of these cross-sections on the total performance of the micromixer. Here, mixing performance in a spiral micromixer with different channel cross-sections is evaluated experimentally and numerically in the Re range of 0.001 to 50. The accuracy of the 3D-finite element model was first verified at different flow rates by tracking the mixing index across the loops, which were directly proportional to the spiral radius and were hence also proportional to the Dean flow. It is shown that higher flow rates induce stronger vortices compared to lower flow rates; thus, fewer loops are required for efficient mixing. The numerical study revealed that a large-angle outward trapezoidal cross-section provides the highest mixing performance, reaching efficiencies of up to 95%. Moreover, the velocity/vorticity along the channel length was analyzed and discussed to evaluate channel mixing performance. A relatively low pressure drop (<130 kPa) makes these passive spiral micromixers ideal candidates for various lab-on-chip applications.

Visualization of flow over a thick airfoil with circular cross-sectional riblets at low Reynolds numbers

2019 ◽  
Vol 22 (5) ◽  
pp. 877-888 ◽  
Author(s):  
Mehrdad Nafar-Sefiddashti ◽  
Mahdi Nili-Ahmadabadi ◽  
Behnam Saeedi-Rizi ◽  
Jalal Pourhoseini
Keyword(s):  
Reynolds Numbers ◽  
Cross Sectional ◽  
Low Reynolds Numbers ◽  
Thick Airfoil ◽  
Low Reynolds

Numerical Investigation on Turbulence Statistics and Heat Transfer of a Circular Jet Impinging on a Roughened Flat Plate

2021 ◽  
Vol 13 (4) ◽  
Author(s):  
Abdulrahman Alenezi ◽  
Abdulrahman Almutairi ◽  
Hamad Alhajeri ◽  
Abdulaziz Gamil ◽  
Faisal Alshammari
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Numerical Study ◽  
Roughness Element ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Target Plate ◽  
Cross Sectional ◽  
Flow Physics ◽  
Baseline Case

Abstract A detailed heat transfer numerical study of a three-dimensional impinging jet on a roughened isothermal surface is presented and is investigated from flow physics vantage point under the influence of different parameters. The effects of the Reynolds number, roughness location, and roughness dimension on the flow physics and heat transfer parameters are studied. Additionally, the relations between average heat transfer coefficient (AHTC) and flow physics including pressure, wall shear and flow vortices with thermodynamic nonequilibrium are offered. This paper studies the effect of varying both location and dimension of the roughness element which took the shape of square cross-sectional continuous ribs to deliver a favorable trade-off between total pressure loss and heat transfer rate. The roughness element was tested for three different radial locations (R/D) = 1, 1.5, and 2 and at each location its height (i.e., width) (e) was changed from 0.25 to 1 mm in incremental steps of 0.25. The study used a jet angle (α) of 90 deg, jet-to-target distance (H/D = 6), and Re ranges from 10,000 to 50,000, where H is the vertical distance between the target plate and jet exit. The results show that the AHTC can be significantly affected by changing the geometry and dimensions of the roughness element. This variation can be either an augmentation of, or decrease in, the (HTC) when compared with the baseline case. An enhancement of 12.9% in the AHTC was achieved by using optimal location and dimensions of the roughness element at specific Reynolds number. However, a diminution between 10% and 30% in (AHTC) was attained by the use of rib height e = 1 mm at Re = 50k. The variation of both rib location and height showed better contribution in increasing heat transfer for low-range Reynolds numbers.

Characterization of drag reduction performance over rotating microgrooves with different cross-sections

2019 ◽  
Vol 234 (6) ◽  
pp. 1746-1758
Author(s):  
Suping Wen ◽  
Wenbo Wang ◽  
Zhixuan Zhang
Keyword(s):  
Drag Reduction ◽  
Cross Sections ◽  
Turbulence Intensity ◽  
Reynolds Numbers ◽  
Cross Sectional ◽  
Dimensionless Velocity ◽  
Velocity Shift ◽  
Maximum Drag Reduction ◽  
Sectional Parameters

This paper presents a study of cross-sectional parameters and optimal drag reduction performance specifically for drag reduction in rotating microgroove applications. Rotating triangular microgrooves with nine asymmetrical and symmetrical cross-sections were numerically studied. In addition, a representative symmetrical rotating microgroove was experimentally tested. Positive asymmetrical microgrooves (including symmetrical microgrooves) were found to be sensitive to rotating Reynolds numbers and produced more significant drag reduction. Compared with a dimensioned asymmetry variable and other dimensionless parameters, the dimensionless asymmetry variable i+ could be used to describe drag reduction performance, which captured both the influence of microgroove cross-sectional asymmetry and turbulence intensity. A maximum drag reduction of up to 8.9% was obtained at 9.2 i+. With the exception of the torque, the velocity shift obtained from dimensionless velocity profiles could also be used to predict drag reduction performance, which has the potential for wider and more comprehensive application for any drag reduction technology.

Numerical study of instability mechanisms in a circular jet at low Reynolds numbers

2012 ◽  
Vol 64 ◽  
pp. 1-18 ◽  
Author(s):  
Trushar B. Gohil ◽  
Arun K. Saha ◽  
K. Muralidhar
Keyword(s):  
Numerical Study ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Low Reynolds

Navier-Stokes Simulations of a Novel Viscous Pump

1997 ◽  
Vol 119 (2) ◽  
pp. 372-382 ◽  
Author(s):  
M. C. Sharatchandra ◽  
Mihir Sen ◽  
Mohamed Gad-el-Hak
Keyword(s):  
Numerical Study ◽  
Slip Flow ◽  
Reynolds Numbers ◽  
Point Of View ◽  
Navier Stokes ◽  
Low Reynolds Numbers ◽  
Plate Spacing ◽  
Slip Effects ◽  
Finite Volume Approach ◽  
Flow Effects

A numerical study of flow in a novel viscous-based pumping device appropriate for microscale applications is described. The device, essentially consisting of a rotating cylinder eccentrically placed in a channel, is shown to be capable of generating a net flow against an externally imposed pressure gradient. Navier-Stokes Simulations at low Reynolds numbers are carried out using a finite-volume approach to study the influence of various geometric parameters. Slip effects for gas flows are also briefly investigated. The numerical results indicate that the generated flow rate is a maximum when the cylinder is in contact with a channel wall and that an optimum plate spacing exists. These observations are in excellent agreement, both qualitatively and quantitatively, with a previous experimental study. Furthermore, it is shown that effective pumping is obtained even for considerably higher Reynolds numbers, thereby extending the performance envelope of the proposed device to non-microscale applications as well. Finally, slip-flow effects appear to be significant only for Knudsen numbers greater than 0.1, which is important from the point of view of microscale applications.

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