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Boundary Layer Control with Injection and Suction Through a Porous Wall

Boundary Layer Control with Injection and Suction Through a Porous Wall. By Crisen McKenzie. Why Control Boundary Layer. Preventing flow separation Controlling flow turbulence Heat transfer Increasing/Decreasing drag. Suction of the Boundary Layer. Decreases thickness of boundary layer

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Boundary Layer Control with Injection and Suction Through a Porous Wall

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  1. Boundary Layer Control with Injection and Suction Through a Porous Wall By Crisen McKenzie

  2. Why Control Boundary Layer • Preventing flow separation • Controlling flow turbulence • Heat transfer • Increasing/Decreasing drag

  3. Suction of the Boundary Layer • Decreases thickness of boundary layer • Increases heat transfer from body to fluid • Delays flow separation • Allows for less turbulent flow • Decreases maximum velocity downstream of flow

  4. Blowing Into Boundary Layer • Increases thickness of boundary layer • Decreases heat transfer • Allows for more turbulent flow • Flow separation occurs sooner • Greater maximum velocity of downstream to the flow

  5. ANALYSIS

  6. Fluent • 2D Pipe flow with Suction/Injection Pipes located normal to fluid flow • Three conditions • Normal • Suction • Injection

  7. Flow Control Apparatus 3 1 0.4 m 2 • Inlet • Outlet • Suction Pipes

  8. Regular Pipe flow • Regular Poiseuille flow • Inlet Pressure: 10 kPa • Outlet Pressure: ambient

  9. Regular Mainstream Flow w/ No Outer Disturbances Boundary Layer Thickness

  10. Suction Boundary Conditions • Regular poiseuille flow • Inlet pressure: 10 kPa • Outlet pressure: ambient • Suction pipe pressure: -1kPa

  11. Normal vs. Suction Increased velocity close to wall Boundary Layer Thickness Boundary Layer Thickness Velocity(m/s) Velocity(m/s)

  12. Injection Boundary Conditions • Regular poiseuille flow • Inlet pressure: 10 kPa • Outlet pressure: ambient • Injection pipe pressure: 1 kPa

  13. Normal vs. Injection Decreased velocity close to wall Boundary Layer Thickness Boundary Layer Thickness Velocity(m/s) Velocity(m/s)

  14. Velocity Graphs Injection Suction

  15. Cross-sectional View of Velocity Profile 1 m Down Pipe

  16. Cross-sectional View of Velocity Profile 1 m Down Pipe Tube Wall

  17. Turbulence Boundary Layer Injection Suction

  18. Cross-Sectional View of Turbulence 1 m Down Pipe

  19. Cross-Sectional View of Turbulence 1 m Down Pipe Tube Wall

  20. Heat Transfer • Lower skin friction Cf means lower heat transfer

  21. Heat Transfer Graph Injection Suction Tw = 100 K T∞ = 300 K

  22. Applications • Preventing flow separation on wing. • Decreasing parasitic drag on wing. • Keeping turbine blades cool • Decreasing boundary layer interference in wind tunnels. • etc

  23. Conclusion • Controlling boundary layer can be very powerful when used. • Used quite heavily in the aerospace environment. • Both Suction and Blowing have their Pros and Cons and Used for different applications

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