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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

    on top o