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Journal of Engineering Technology Volume 3, Issue 2, July, 2015, Pages. 158-173

Numerical Investigation of Drag Reduction Using

Electromagnetic

Reza Soleimanpour1* and Kazem Kalantari

2

1,2- MSc of Mechanical Engineering, Kish International Branch, Islamic Azad Univesity,

Kish Island, Iran

Abstract. In recent years, numerous experimental and numerical methods

have been used for drag reduction. One of the most effective methods to

reduce drag and turbulent boundary layer control is applying the

electromagnetic. The aim of this project is to reduce drag and increase lift by

using the electromagnetic effect. Various studies conducted by researchers in

the field using electromagnetic drag reduction are investigated. In addition,

the use of electromagnetic modes to reduce the drag of a flat plate using

numerical methods and software CFX and comsol simulated. Research

carried out by different people, as well as simulations show that the drag

reduction of up to 50 percent through the use of electromagnetic forces to the

fluid is possible.

Keywords: Hydrofoil, flow separation, dragforce, electromagnetic, CFX.

1 Introduction

One of the effective methods to reduce drag and turbulence boundary control

is using electromagnetic, or properly is forces caused by the

electromagnetic. It should be noted that if a fluid such as water that has

electrical conductivity, passes from the electromagnetic field, forces that is

knownLorentz force applied to it, this force is applied in different ways in

order to reduce drag.In most studies, direction ofLorentz force was in fluids

direction that has actually acted as an accelerator in the fluid direction and as

an electromagnetic pump [1]. Gailitis and Lielausis [quotedfrom reference

[6] was the first group who used Lorentz force to control fluid. In

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Journal of Engineering Technology Volume 3, Issue 2, July, 2015, Pages. 158-173

theiranalysis, they appliedLorentzforce to the fluid laminar boundarylayer in

fluid direction in order to create a thrust force and also prevent

fromtransferring of laminar boundary layer to turbulent layer and increasing

of thethickness of boundary layer [quoted from reference 2]. Shtern and

Nosenchuckshowed that the Blasius profile of boundary layer when the

Lorentzforce is appliedit become more stable.

Nosenchuck and his team [quoted from [7] studied viscous drag reduction on

Boundarylayer, usingLorentzforce, In their experiments , Lawrence force is

in perpendicular direction to the wall and perpendicular to the flow direction.

Their aim has been drag reductionbycontrolling turbulenceBoundary layer.

The results were not showing drag reduction and could not achieve the

resultsby applying Lorentz forcein drag reduction.Bandyopadhyayand

Castanoplaced arrangement of the electrodes and magnets as Henoch, but

considereddirection of flow perpendicular to the Lawrence force. They

connected electrodes to an alternating current that causes the Lawrence force

applied to the fluid, shift with flow frequency.

In fact, an oscillatory force is applied to the fluid and as the same as the

surface of the object that fluid is moving has a swinging motion. Simulations

show 30 percent of drag reduction that of course depends on the current

frequency, or in other words the Lorentz force. The cause of drag reductionis

turbulence reduction ofBoundary layer through combining

ofvortexresonance in Boundary layer and also applied Lorentzforce, but in

laboratory method they could not reach the amount of drag reduction

obtained in the simulation. In the laboratory method, they obtained only 3%

of drag reduction [quoted from reference 9].

2 Statement of the problem

Thisstudy has been evaluatedairfoil NACA 0012 geometry. In order to draw

the desired geometry in Gambit software, the following equation was used.

First, using this relationship and ratio x / c between 0 to 1 and chord one,

about 100 data obtained with different coordinates , saved in TEXT format ,

called in the Gambit software and then is drawing. In this software,

afterdrawing of lines, meshing(channeling) of computing field is discussed.

The final form of the descriptive geometry is in the form of (1). The

boundary conditions used for the computational domain of the boundary

condition is pressure far field.

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Journal of Engineering Technology Volume 3, Issue 2, July, 2015, Pages. 158-173

2 3

4

0.298222773 0.127125232

.594689181 0.357906 0.291984971

0.105174696

x x

c c

x xy c o

c c

x

c

Figure. 1. Geometry of a NACA 0012 with chord equal 1

After drawing of geometry and meshing in related geometry Gambit

software, it is called in CFX software. To simulate, the initial conditions is

required, to do so, the data in the paper [41] was applied as table (1).

Table.1. the initial conditions used in the simulation

entrance

speed(m/s) 05

density(kg/m3) 352/1

temperature(oC) 35

viscosity(kg/ms) 71218/1

Mach 10/5

3 Independence of the results from meshing

In each simulation, in order to ensure computational domain and

independence of meshing solutions must ensure proper meshing. In this

regard, the airfoil has been evaluated using different meshing and comparing

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Journal of Engineering Technology Volume 3, Issue 2, July, 2015, Pages. 158-173

the results to predict the lift coefficient on the angle of attack of 2 degree,

and the results for (2) is given. As seen, the results for a lattice of up to

70,000 predict almost equal results, so the same number of lattice will be

used to continue the work.

Figure. 2. Study of meshing and the independence solution results from the number of

lattice

4 Authentication method

Figure (3) shows the lift coefficient at different angles of attack for the

boundary conditions mentioned in the table (1) and its comparison with the

data in the paper [41]. As you can see, the results of the simulation for angles

of attack higher than 6, gradually is increasing the error. The reason for this

difference may be due to segregation, which occurring during the flow, the

model could not predict it. The process for different turbulence models and

meshing more than 70000 has been investigated and still has erroneous

results. Hence it is evident that CFX software for this case study does not

predict a good outcome. So considering the purpose of this project which is

the use of electromagnetic force, and taking into account the capability of

COMSOL software, as described here the COMSOL software is used.

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Journal of Engineering Technology Volume 3, Issue 2, July, 2015, Pages. 158-173

Figure. 3. Comparing the results of CFX software and experimental data

5 Computational domain

In order to predict the flow behavior in COMSOL software, the intended

computational domain was in the form of figure (4) respectively. It is seen

that the computing field about 200 times the chord that is equal 1/8 (Figure

(5)) is drawn in the back and about 100 times in the front of airfoil. The

implied Boundary conditions are based on the figure. The initial conditions

used based on the table (2) with the exception that the Reynolds number of

the basic chord is 6 106.

Figure. 4. computational domain for simulation in COMSOL software

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Journal of Engineering Technology Volume 3, Issue 2, July, 2015, Pages. 158-173

Figure. 5. Airfoil NACA0012 under reviewing

As mentioned above, the computational domain is built with 200 times chord

in the back and 100 times in front of airfoil. For this field, meshing has been

established in the form of (6). It is observed that the field has regularly

meshing.

Figure. 6. Meshing of computational domain in COMSOL software

6 Solution validation

In order to validate solutions and also COMSOL software, according to

figure (7) and (8 and comparing of the results for the lift and pressure

coefficient is discussed. As you can see, the reported results to the angle of

attack were 14 degrees and it is obvious that the results of the simulation are

consistent with high accuracy on the data in the paper [41]. Thus, according

to these results, it is obvious that the method is suitable for simulation.

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Journal of Engineering Technology Volume 3, Issue 2, July, 2015, Pages. 158-173

Figure. 7. Comparison of numerical result (continuous line) with experimental data

(symbols) for air to predict lift coefficient

Figure. 8. Calculating of numerical coefficient (solid line) and its comparison with

experimental data (symbols)

Considering that the aim of the study is drag reduction and since due to flow

separation at high angles of attack also drag is increasing, studies should be

done especially at this point. In this regard, Figure (9) shows the speed

contour at 14 degrees of angle of attack. It is observed that the flow lines

have fractures due to the angle of attack. It is added there is flow separation

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