fluid dynamics Flashcards
What is the edge facing the direction of flow on a flat plate called?
The leading edge.
What is the rear edge of a flat plate in the direction of flow called?
The trailing edge.
Near the leading edge of a flat plate, what type of boundary layer is formed?
The boundary layer is wholly laminar.
For a laminar boundary layer, what is the velocity distribution?
The velocity distribution is parabolic.
How does the thickness of the boundary layer (δ) change with distance from the leading edge x?
δ increases with distance from the leading edge x.
What happens to the boundary layer as δ increases with x?
More fluid is slowed down by the viscous boundary, becomes unstable, and breaks into a turbulent boundary layer over a transition region.
In a turbulent boundary layer on a smooth boundary, what remains laminar?
A very thin layer called the laminar sublayer.
What are the velocity distributions in the turbulent boundary layer?
Log law or Prandtl’s one-seventh power law.
How does the boundary layer thickness δ change as the free stream velocity U increases?
δ decreases as U increases.
How does δ change as kinematic viscosity (ν) increases?
δ increases as kinematic viscosity (ν) increases.
What is the relationship between τ₀ and δ?
τ₀ ≈ µ (U / δ).
How does τ₀ change as x increases in a laminar boundary layer?
τ₀ decreases as x increases.
When the boundary layer becomes turbulent, how does τ₀ behave with increasing x?
It shows a sudden increase and then decreases with increasing x.
What happens to boundary layer growth when U increases in the downward direction?
Boundary layer growth is reduced.
What occurs when U decreases in the downward direction?
Flow near the boundary is further retarded, boundary layer growth is faster and is susceptible to separation.
