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Air microbubbles drag reduction

Submitted to :

Prof.Dr/ Hassan el gamal

Prof.Dr/ Rola afify

Prof.Dr/ Khaled el sherbiny

Prof.Dr/ Kamel el shorbagy

Prof.Dr/ kamal abdelaziz

Submitted by :

Amr sameh Mohamed

Youssef Mohamed morsy

Amr adel ali

Mohamed ali mostafa

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Outline :

  • Drag force

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  • Air microbubbles

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  • Ship resistance

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  • Components

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  • Conclusion and results

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Drag Force ( Total resistance ) :

  • Definition
  • Types of drag force ( total resistance )

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Reddy

Rw

RF

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RT = RF + Rw + Reddy

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Drag reduction techniques:�( microgrooves, coatings, addictive injections (such as polymer, surfactant and microbubbles)

  • Why using microbubbles ?

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What is air microbubbles:

  • A microbubble is a gas cavity in liquid. The gas can be air, nitrogen, or a high molecular weight gas.

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Drag reduction by injection of microbubbles:

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Micro-Bubble Characteristics:

  • Bubble size :

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  • Location of micro bubbles :

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Ship resistance

wave making resistance

Eddy resistance

Friction resistance

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Wave making resistance

  • Waves
  • Pressure field
  • Drag force

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Wave pattern

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  • The bow and stern wave systems generated by a ship

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Wave pattern generated by a moving object in the water

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Ship wave resistance

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Decrease wave making resistance

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Attaching bulbous bow

  • Primary wave
  • Secondry wave
  • Reduce drag force
  • Reduce 7% in fuel consumption

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Frictional resistance

The frictional resistance depends on:

1.the size of the wetted area,

2.surface roughness,

3.Viscosity

Represent 70-85% of the ship total resistance

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Friction resistance reduction

  • Using Air lubrication injection
  • Reduce up to 11%

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resistance calculations

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Prochaska's method

Y=mX+c

Cv=(1+K)Cf

Cw=Ct-Cv

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Components�

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stand �

  • A stand of steel with a box to include the water also to fix motor , pump and inverter .

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motor�

  • A motor (3 phase) to convert the electrical power to a mechanical power with a moving parts

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coupling �

  • A coupling is a device that is used to connect two shafts together for power transmission.

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pump�

  • pump, a device that expends energy in order to raise, transport, or compress fluids.

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inverter�

  • Electric motor speed control. Inverter circuits designed to produce a variable output voltage range are often used within motor speed controllers.

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load cell�

  • A load cell is adevice that is used to measure weight and ,con sequently , the forces exerted , both in compression and in teraction .
  • Also : transducer which converts force into a measurable electrical output.

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hx711�

  • It as built-in a preamplifier that is used to amplify low voltage signals.

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arduino�

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two ships�

  • A two design of ships which made to avoid drag reduction one of the ships depend in compreesed air which cases air micro bubbles and the second is a normal ship with special bow.

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directions sheet�

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compressor

  • an instrument or device for compressing something.

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pressure Regulators(controller)�

  • It is a device to controll the amount of compressed air

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Experimental steps & Output

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Experimental steps & Output

  • Relative motion
  • Actually, the sea is constant while the ships are move in it
  • In Experiment, the ships are constant while the water is move in tank

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Experimental steps & Output

  • Type of experimental
  • Uncompressed air ship (black ship)
  • Compressed air ship (white ship)

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Uncompressed air ship (black ship)�

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Relation between frequency &force�for black ship

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Force (mN)

0

0

0.0788

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0.0875

43

0.15

45

0.3

49

0.351

53

0.365

55

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Compressed air ship (white ship)�

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Relation between frequency &force�for white ship

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Relation between air flow rate & force�for white ship

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Layer of air micro bubbles

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Conclusion

  • The compressed ship is better than the uncompressed ship
  • Less drag force
  • Less fuel consumption

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Thank you