Why does a laminar boundary layer become turbulent?

When the velocity was low, the dyed layer remained distinct through the entire length of the large tube. When the velocity was increased, the layer broke up at a given point and diffused throughout the fluid’s cross-section. The point at which this happened was the transition point from laminar to turbulent flow.

How does laminar flow change to turbulent flow?

As the Reynolds number increases, such as by increasing the flow rate of the fluid, the flow will transition from laminar to turbulent flow at a specific range of Reynolds numbers, the laminar–turbulent transition range depending on small disturbance levels in the fluid or imperfections in the flow system.

Can a boundary layer go from turbulent to laminar?

It has been shown experimentally that quite large departures occur from the universal inner-law velocity distribution in the presence of severe favourable pressure gradients in turbulent boundary layers and that these departures are associated with the tendency for the turbulent boundary layer to revert to a laminar …

How does a turbulent boundary layer form?

A boundary layer may be laminar or turbulent. Thus there is an exchange of mass, momentum and energy on a much bigger scale compared to a laminar boundary layer. A turbulent boundary layer forms only at larger Reynolds numbers. The scale of mixing cannot be handled by molecular viscosity alone.

Why are turbulent boundary layers thicker?

This means that because of the greater velocity gradient at the wall the frictional shear stress in a turbulent boundary is greater than in a purely laminar boundary layer.

What becomes turbulent flow?

Laminar–turbulent transition For flow in a pipe of diameter D, experimental observations show that for “fully developed” flow, laminar flow occurs when ReD < 2300 and turbulent flow occurs when ReD > 2900.

Why is turbulent boundary layer thicker than laminar boundary layer?

. This means that because of the greater velocity gradient at the wall the frictional shear stress in a turbulent boundary is greater than in a purely laminar boundary layer.

Why does boundary layer separation occur?

The phenomenon is termed as separation of boundary layer. Separation takes place due to excessive momentum loss near the wall in a boundary layer trying to move downstream against increasing pressure, i.e., , which is called adverse pressure gradient.

What do you mean by laminar and turbulent boundary layer?

There are two different types of boundary layer flow: laminar and turbulent. Laminar boundary layer flow. The laminar boundary is a very smooth flow, while the turbulent boundary layer contains swirls or “eddies.” The laminar flow creates less skin friction drag than the turbulent flow, but is less stable.

What is the difference between laminar and turbulent layer?

A boundary layer may be laminar or turbulent. A laminar boundary layer is one where the flow takes place in layers, i.e., each layer slides past the adjacent layers. This is in contrast to Turbulent Boundary Layers shown in Fig.6.2 where there is an intense agitation.

Where is the flow in the plate boundary layer laminar?

Near the leading edge of the surface of the plate, where the thickness is small, the flow in the boundary layer is laminar though the main flow is turbulent.

What is the transition zone of a turbulent boundary layer?

It will lead to a transition from laminar to turbulent boundary layer. This small length over which the boundary layer flow changes from laminar to turbulent will be termed as transition zone. BC, in above figure, indicates the transition zone.

What is a laminar zone?

Length of the plate from the leading edge up to which laminar boundary layer exists will be termed as laminar zone. AB indicates the laminar zone in above figure. Length of the plate from the leading edge up to which laminar boundary layer exists i.e. laminar zone will be determined with the help of following formula as mentioned here.