Sunday, 19 August 2018

Potential Flow

“When a flow is both frictionless and irrotational, pleasant things happen.” – F.M. White, Fluid Mechanics 4th ed.

potential flow
irrotational flow, a potential flow is characterized by an irrotational velocity field

in potential flow, velocity is described as gradient of velocity potential (P182 fundametal of aerodynamics, Andersion)

The irrotationality of a potential flow is due to the curl of the gradient of a scalar always being equal to zero.

Features

  • potential flow describes the velocity field as the gradient of a sclar function: the velocity potential.
  • viscosity = 0
  • frictionless, μ = 0
  • potential flow could be incompressible or compressible

Assumptions

  • irrotational flow

Why is irrotational flow called potential flow? because irrotational flows can be described by the velocity potential, φ

1 potential flow vs inviscid flow

(The terms potential flow and inviscid flow are almost synonymous and are frequently used interchangeably( panton, incompressible flow)

2 Applications

  • potential flow is a valid approximation for several applications,
    • flow around aircraft
      • For instance, in computational fluid dynamics, one technique is to couple a potential flow solution outside the boundary layer to a solution of the boundary layer equations inside the boundary layer.
    • groundwater flow
    • acoustics
    • water waves
    • electroosmotic flow

3 Limits

  • In flow regions where vorticity is known to be important,

such as wakes and boundary layers, potential flow theory is not able to provide reasonable predictions of the flow

4 References

Chapter 6: Ideal Flow. Kundu, fluid mechanics Chapter 18: Ideal Flows in a Plane Panton, Ronald L. Incompressible Flow. 4th ed. Wiley, 2013. ISBN: 9781118013434. file:///c:/akmkemin/Backup/academic_theory_books/potential-flow file:///c:/akmkemin/Backup/academic_theory_books/potential-flow/Potential-Flow-Theory-mit.pdf

Created: 2018-08-19 Sun 18:42

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