Experimental Study of Drag Reduction on Circular Cylinder and Reduction of Pressure Drop in Narrow Channels by Using a Cylinder Disturbance Body

2014 ◽  
Vol 493 ◽  
pp. 198-203 ◽  
Author(s):  
Wawan Aries Widodo ◽  
Nuzul Hidayat
Keyword(s):  
Pressure Drop ◽  
Circular Cylinder ◽  
Drag Reduction ◽  
Drag Force ◽  
Bluff Body ◽  
Position Angle ◽  
Narrow Channel ◽  
Lower Side ◽  
Cross Sectional ◽  
Narrow Channels

This paper present the results of drag reduction on circular cylinder and reduction of pressure drop in narrow rectangular channels by using circular disturbance body. This study focused on the phenomenon when the flow through the arrangement of the circular cylinder, separation will occur at a specific point on a circular cylinder resulting drag force. When the separation can be delayed so that the resulting drag force will be smaller. This can be done in various ways, one of which is by using a cylinder disturbance body on the upper and lower side near the bluff body. This study will be conducted in a wind tunnel experiments which have narrow channels with a square cross-sectional area of 125 mm x 125 mm and a blockage ratio of 26.4% and 36.4%. Specimens used circular cylinder with 25 mm diameter (d/D= 0.16) and 37.5 mm (d/D= 0.107) as well as the circular disturbance body with a diameter of 4 mm. cylinder disturbance body placed on the upper and lower side with the position α=200 to 600 and spacing (δ=0.4 mm) to the main circular cylinder. Reynolds number based on the hydraulic diameter of 5.21×104 to 15.6×104. The results of this research show the effect of using circular disturbance body on circular cylinder and the characteristics of fluid flow on a narrow channel square cross section. At a certain position of the circular disturbance body provide value pressure drop reduction on narrow channels and drag reduction when compared to a single circular cylinder. From the experimental data presented in this paper it is observed that the position angle of circular disturbance body to reduce drag force on a circular cylinder and reducing the pressure drop in the channel are at angle 200 and 300 for D=25 mm, and 200, 300 and 400, respectively, for D= 37.5 mm then the best reduction for both cylinders are at an angle of 300.

Reduction of Drag Force on a Circular Cylinder and Pressure Drop Using a Square Cylinder as Disturbance Body in a Narrow Channel

2014 ◽  
Vol 493 ◽  
pp. 192-197 ◽  
Author(s):  
Wawan Aries Widodo ◽  
Randi Purnama Putra
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Wind Tunnel ◽  
Circular Cylinder ◽  
Drag Force ◽  
Bluff Body ◽  
Flow Characteristics ◽  
Narrow Channel ◽  
Square Cylinder ◽  
Cross Sectional

Many studies related with characteristics of fluid flow acrossing in a bluff body have been conducted. The aim of this research paper was to reduce pressure drop occuring in narrow channels, in which there was a circular cylindrical configuration with square cylinder as disturbance body. Another goal of this research was to reduce the drag force occuring in circular cylinder. Experimentally research of flow characteristics of the wind tunnel had a narrow channel a square cross-section, with implemenred of Reynolds number based on the hydraulic diameter from 5.21x104 to 1.56x105. Wind tunnel that was used had a 125x125mm cross-sectional area and the blockage ratio 26.4% and 36.4%. Specimen was in the form of circular cylinder and square cylinder as disturbance body. Variation of angle position was the inlet disturbance body with α = 200, 300, 400, 500 and 600, respectively. The results was obtained from this study was Reynolds Number value was directly linear with pressure drop there, it was marked by increasing of Reynolds number, the value was also increasing pressure drop. Additional information was obtained by adding inlet disturbance body shaped of square cylinder on the upstream side of the circular cylinder that could reduce pressure drop in the duct and reduce drag happening on a circular cylinder. The position of the optimum angle to reduce pressure drop and drag force was found on the inlet disturbance body with angle α = 300.

scholarly journals Drag Reduction of Circular Cylinder using Square Disturbance Body at 600 Angle by 2D Numerical Simulation Unsteady-RANS

2017 ◽  
Author(s):  
Rina ◽  
Ruzita Sumiati
Keyword(s):  
Circular Cylinder ◽  
Drag Force ◽  
Flow Separation ◽  
Bluff Body ◽  
Aerodynamic Force ◽  
Narrow Channel ◽  
Main Body ◽  
Transition Flow ◽  
Rans Models ◽  
Force Reduction

Drag is an aerodynamic force that appears when the flow past the bluff body circular cylinder. Drag strongly influenced by the flow separation point. One of the ways reducing the drag force that is to control the flow by placing the disturbance body on the upstream side at a certain angle. Previous research has found at 60º angle of flow separation is faster than a single cylinder that produced greater drag. Therefore, this research was conducted to reduce the drag force on the corner with disturbance dimension variation. This research was carried out numerically using a FLUENT 6.3.26 CFD software in 2D unsteady viscous-RANS models Turbulence Model-Shear-Stress Transport (SST) k-ω in a narrow channel. The geometry is simulated in a circular cylinder as the main body and the square cylinder as a disturbance body being placed in front of the main body by s/D ratio. Dimensions of disturbance body varied at (s) 0,1; 0,2; 0,3; 0,4 dan 0,5 mm with a gap (δ=0,4mm). Reynolds number based on the diameter of the cylinder, ie ReD 2,32x104. The simulation results show that the transition flow on shifting 60º SDB angle for all SDB dimensional variations do not produce turbulent. The optimum condition for the drag force reduction is s/D = 0.008 about 48 %.

scholarly journals STUDI NUMERIK PRESSURE DROP PADA SILINDER TANDEM DENGAN PENAMBAHAN SPLITTER PLATE DAN VORTEX GENERATOR DI PENAMPANG SEMPIT

Otopro ◽  
2021 ◽  
pp. 15-20
Author(s):  
Diastian Vinaya Wijanarko
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Circular Cylinder ◽  
Numerical Study ◽  
Vortex Generator ◽  
Splitter Plate ◽  
Blockage Ratio ◽  
Cross Sectional ◽  
The Cross

The numerical study of pressure drop on a tandem cylinder with the addition of a splitter plate and a vortex generator with the effect of a blockage ratio has been completed. The cross-sectional height and diameter of the cylinder in this study used H= 125 mm and D= 37.5 mm, respectively. The blockage ratio is 30%. The Reynolds number (Re) is 52100 ≤ Re ≤ 156000. The distance between cylinders is 5 to 8, where “s” is the distance from cylinder one to cylinder two. The dimensions of the splitter plate are L=D, L=1,5D, and L=2D where "L" is the length of the splitter plate, while the thickness in this study is 1, 75mm. The dimensions of the vortex generator in this study are used those of Hu, et al. [6]. The angle of the vortex generator is = 350 while the length of the vortex generator is H = 3 mm. All variations of this numerical study were carried out using the URANS (Unsteady Reynold Average Navier Stoke) method with a Reynolds number (Re) 52,100 Re 156,000. The smallest pressure drop value is obtained at the Reynolds number 52.100 for all variations, while the highest Reynolds number is obtained at Re 156.000. the addition of a splitter plate and a vortex generator, gives a higher pressure drop when compared to a circular cylinder.

Drag Reduction of Bluff Bodies by Surface Control Based on a Force Theory

2007 ◽  
Author(s):  
Shih-Hao Yang ◽  
Chien C. Chang ◽  
Chin-Chou Chu ◽  
Shi-Hua Liao ◽  
R. L. Chern
Keyword(s):  
Circular Cylinder ◽  
Drag Reduction ◽  
Bluff Body ◽  
The Body ◽  
Bluff Bodies ◽  
Rational Basis ◽  
Surface Control

In the present study, we show how drag reduction of a bluff body can be achieved on a rational basis of a force theory. The force theory indicates where is the best location to apply the surface control to minimize the drag on the body. In particular, the method of drag reduction is illustrated for flow around a circular cylinder. It is shown that drag reduction for the circular cylinder can be as efficient as 46.5%.

Numerical Effect of Airflow From a Lower Canopy (Bluff Body) Into an Upper Canopy in Steady and Turbulent Condition

2008 ◽  
Author(s):  
Mohammad J. Izadi
Keyword(s):  
Drag Force ◽  
Bluff Body ◽  
Cross Sectional Area ◽  
The Body ◽  
Bluff Bodies ◽  
Variable Cross ◽  
Sectional Area ◽  
Cross Sectional ◽  
Varied Form ◽  
Two Bodies

In this paper, a 3-D flow field around two bluff bodies in an incompressible fluid is modeled [1]. Formations of these two bodies are top to top (One on the top of the other) with respect to the center of each other. The lower on has a constant cross sectional area with a vent of air at its apex and the upper one has a variable cross sectional area with no vent on it. The vertical distances between the bluff bodies, the cross sectional area, and also the vent ratio of bluff bodies are varied here. Vertical distances of these two bodies are varied form zero to half, equal, double and triple the radius of the body with a vent on it (lower body). Flow condition is considered 3D, steady, turbulent, and incompressible. The drag force on each body and also the pressure around the two bodies are calculated. From the numerical results, it can be seen that, the drag force is constant over the range of zero to twenty percent of the vent ratios and for higher vent ratios when the upper bluff body is smaller than the lower one the drag force decreased, and it increased when the upper bluff body is larger than the lower one.

Minimum power consumption for drag reduction on a circular cylinder by tangential surface motion

2013 ◽  
Vol 715 ◽  
pp. 597-641 ◽  
Author(s):  
Ratnesh K. Shukla ◽  
Jaywant H. Arakeri
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Power Consumption ◽  
Drag Reduction ◽  
Drag Force ◽  
Potential Flow ◽  
Power Loss ◽  
Tangential Velocity ◽  
Two Dimensional ◽  
Tangential Surface

AbstractWe investigate the effect of a prescribed tangential velocity on the drag force on a circular cylinder in a spanwise uniform cross flow. Using a combination of theoretical and numerical techniques we make an attempt at determining the optimal tangential velocity profiles which will reduce the drag force acting on the cylindrical body while minimizing the net power consumption characterized through a non-dimensional power loss coefficient (${C}_{\mathit{PL}} $). A striking conclusion of our analysis is that the tangential velocity associated with the potential flow, which completely suppresses the drag force, is not optimal for both small and large, but finite Reynolds number. When inertial effects are negligible ($\mathit{Re}\ll 1$), theoretical analysis based on two-dimensional Oseen equations gives us the optimal tangential velocity profile which leads to energetically efficient drag reduction. Furthermore, in the limit of zero Reynolds number ($\mathit{Re}\ensuremath{\rightarrow} 0$), minimum power loss is achieved for a tangential velocity profile corresponding to a shear-free perfect slip boundary. At finite $\mathit{Re}$, results from numerical simulations indicate that perfect slip is not optimum and a further reduction in drag can be achieved for reduced power consumption. A gradual increase in the strength of a tangential velocity which involves only the first reflectionally symmetric mode leads to a monotonic reduction in drag and eventual thrust production. Simulations reveal the existence of an optimal strength for which the power consumption attains a minima. At a Reynolds number of 100, minimum value of the power loss coefficient (${C}_{\mathit{PL}} = 0. 37$) is obtained when the maximum in tangential surface velocity is about one and a half times the free stream uniform velocity corresponding to a percentage drag reduction of approximately 77 %; ${C}_{\mathit{PL}} = 0. 42$ and $0. 50$ for perfect slip and potential flow cases, respectively. Our results suggest that potential flow tangential velocity enables energetically efficient propulsion at all Reynolds numbers but optimal drag reduction only for $\mathit{Re}\ensuremath{\rightarrow} \infty $. The two-dimensional strategy of reducing drag while minimizing net power consumption is shown to be effective in three dimensions via numerical simulation of flow past an infinite circular cylinder at a Reynolds number of 300. Finally a strategy of reducing drag, suitable for practical implementation and amenable to experimental testing, through piecewise constant tangential velocities distributed along the cylinder periphery is proposed and analysed.

scholarly journals Microfiber Coating for Drag Reduction by Flocking Technology

Coatings ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 464 ◽  
Author(s):  
Mitsugu Hasegawa ◽  
Hirotaka Sakaue
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Circular Cylinder ◽  
Drag Reduction ◽  
Flow Separation ◽  
Bluff Body ◽  
Rigid Surface ◽  
Smoke Flow ◽  
Flexible Fibers ◽  
Transition Delay

The biomimicry of using a hair-like structure is introduced as a drag reduction coating. The hair-like structure consists of an array of microfiber that is introduced as a passive drag reduction device. An effective flow control for a transition delay or a flow attachment is expected via an interaction or counteraction of flexible fibers, compared to the existing passive methods that use a solid or rigid surface device. The effect of the microfiber coating on drag reduction over a bluff-body was experimentally investigated using a circular cylinder in a wind tunnel at Reynolds number of 6.1 × 104. A drag reduction of 32% was obtained when the microfiber coating with a length of 0.012D was located at 40° from the stagnation point. Smoke flow visualization showed that flow separation delay was induced by the microfiber coating when the drag reduction occurred.

Drag Reduction of a Bluff Body by Grooves Laid Out by Design of Experiment

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Seong-Ho Seo ◽  
Chung-Do Nam ◽  
Jung-Young Han ◽  
Cheol-Hyun Hong
Keyword(s):  
Optimal Design ◽  
Circular Cylinder ◽  
Drag Reduction ◽  
Bluff Body ◽  
Wake Flow ◽  
Design Parameters ◽  
Mean Velocity ◽  
Smooth Cylinder ◽  
Layer Flow ◽  
Parameter Values

In this study, we used the Taguchi method to derive the optimal design parameters for the grooves formed on the upper surface of a circular cylinder. Using the derived values of the optimal design parameters, we created grooves on diphycercal the surfaces of a circular cylinder and analyzed the wake flow and the boundary-layer flow of the circular cylinder. The streamwise time mean velocity and turbulence intensity of the wake flow field were used as the characteristics. Based on these characteristics, the optimal design parameter values were selected: n = 3, k = 1.0 mm (k/d = 2.5%), and θ = 60 deg. When the grooved cylinder was used, the streamwise time mean velocity in the wake of the cylinder showed 12.3% recovery, the wake width was reduced by 18.4% compared to the results from the smooth cylinder and we had 28.2% drag reduction from that of smooth cylinder. Also, the flow on the smooth cylinder separated at around 82 deg but the flow separation on a grooved cylinder appeared beyond 90 deg, that reducing the drag.

scholarly journals Effects of Streamlining a Bluff Body in the Laminar Vortex Shedding Regime

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Ritvik Dobriyal ◽  
Maneesh Mishra ◽  
Markus Bölander ◽  
Martin Skote
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Shape Factor ◽  
Bluff Body ◽  
The Body ◽  
Cross Sectional ◽  
Shape Factors ◽  
Rear Part ◽  
Lift And Drag

Abstract Two-dimensional flow over bluff bodies is studied in the unsteady laminar flow regime using numerical simulations. In previous investigations, lift and drag forces have been studied over different cross-sectional shapes like circles, squares, and ellipses. We aim to extend the previous research by studying the variation of hydrodynamic forces as the shape of the body changes from a circular cylinder to a more streamlined or a bluffer body. The different body shapes are created by modifying the downstream circular arc of a circular cylinder into an ellipse, hence elongating or compressing the rear part of the body. The precise geometry of the body is quantified by defining a shape factor. Two distinct ranges of shape factors with fundamentally different behavior of lift and drag are identified. The geometry constituting the limit is where the rear part ellipse has a semi-minor axis of half the radius of the original circle, independent of the Reynolds number. On the other hand, the vortex shedding frequency decreases linearly over the whole range of shape factors. Furthermore, the variation of the forces and frequency with Reynolds number, and how the relations vary with the shape factor are reported.

Microchannels in series connected via a contraction/expansion section

2002 ◽  
Vol 459 ◽  
pp. 187-206 ◽  
Author(s):  
WING YIN LEE ◽  
MAN WONG ◽  
YITSHAK ZOHAR
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Flow Direction ◽  
Pressure Sensors ◽  
Narrow Channel ◽  
Narrow Channels ◽  
Pressure Losses ◽  
Transition Section ◽  
In Series ◽  
Straight Segments

Fluid flow in microdevices consisting of pairs of microchannels in series was studied. The dimensions of the channels are about 40 μm × 1 μm × 2000 μm for the wide and about 20 μm × 1 μm × 2000 μm for the narrow channels. Pairs of wide and narrow channels, with integrated pressure sensors, are connected via transition sections with included angles varying from 5° to 180°. Minor pressure losses (not due to friction) were studied by passing nitrogen through the channels under inlet pressures up to 60 p.s.i. Each device was tested in the contraction mode, flow from wide to narrow channel, and in the opposite expansion mode, flow from narrow to wide channel. Mass flow rate was first measured as a function of the overall pressure drop. The detailed pressure distribution along the straight segments and around the transition section was then measured in order to understand the flow pattern. The Reynolds number for these flows is less than 1, suggesting the flow to be of the Hele-Shaw type with no separation such that the results for all the devices should be similar. However, the flow rate was found to decrease and the pressure loss to increase significantly with increasing included angle of the transition section, regardless of the flow direction. Flow separation due to the transition sections, if indeed there is any, cannot explain the large pressure drop since the kinetic energy is negligible.

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