Boundary layer, in fluid mechanics, thin layer of a flowing gas or liquid in contact with a surface such as that of an airplane wing or of the inside of a pipe. The fluid in the boundary layer is subjected to shearing forces.

This condition states that the velocity of the fluid at the solid surface equals the velocity of that surface. The result of this condition is that a boundary layer is formed in which the relative velocity varies from zero at the wall to the value of the relative velocity at some distance from the wall.

The momentum of the flat plate is zero and the momentum of the uniform flow has a finite value. When the incoming uniform flow flows over a flat plate, the fluid particles near the plate will stick to the plate (no-slip condition). And hence the boundary layer thickness increases as the fluid moves downstream.

Aerodynamic forces are generated between the fluid and the object. This creates a thin layer of fluid near the surface in which the velocity changes from zero at the surface to the free stream value away from the surface. Engineers call this layer the boundary layer because it occurs on the boundary of the fluid.

When a fluid stream encounters a solid surface that is at rest, the fluid velocity assumes a value of zero at that surface. The velocity then varies from zero at the surface to some larger value sufficiently far from the surface. The development of a boundary layer is caused by the no-slip condition.

In fluid dynamics, Stokes problem also known as Stokes second problem or sometimes referred to as Stokes boundary layer or Oscillating boundary layer is a problem of determining the flow created by an oscillating solid surface, named after Sir George Stokes.

Separation of boundary layer is caused by presence of adverse pressure gradient.

Methods of preventing the separation of boundary layer: Streamlining the body shape. Tripping the boundary layer from laminar to turbulent by provision of surface roughness. Sucking the retarded flow.

What is D’Alembert’s Paradox? Explanation: D’Alembert’s Paradox states that for an incompressible and inviscid flow potential flow, the drag force is equal to zero. The fluid is moving at a constant velocity with respect to its relative fluid.

The wake is the region of disturbed flow (often turbulent) downstream of a solid body moving through a fluid, caused by the flow of the fluid around the body.

In an imaginary fluid that has no friction (an inviscid fluid), there would be no drag, the entropy does not change, and the flow would be reversible. For example, a cylinder in the flow of an inviscid fluid has no vortex shedding and it has no drag, contrary to our practical experience.

Frictional drag comes from friction between the fluid and the surfaces over which it is flowing. The wake is very small, and the drag is dominated by the viscous friction inside the boundary layers. However, as the angle of attack increases, the pressure gradients on the airfoil increase in magnitude.

Because of viscous losses, the stagnation pressure in the wake is lower than the stagnation pressure at the front of the cylinder. However, it has* a higher pressure than the fluid that is moving outside of the wake.

Explanation: cyclone. A cyclone is formed by a very low-pressure system with very high-speed winds revolving around it. The low-pressure region is called the eye of the cyclone.

In meteorology, a low-pressure area, low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. Low-pressure systems form under areas of wind divergence that occur in the upper levels of the atmosphere. The formation process of a low-pressure area is known as cyclogenesis.

Wake lows form due to adiabatic warming in the wake of mature squall lines at the back edge of their rain shields, where evaporative cooling is unable to offset warming due to atmospheric subsidence, or downward motion.

The area of enhanced winds this evening is the result of what is known as a “wake low.” A wake low sometimes forms in the wake of a thunderstorm complex like we had earlier. It is quite rare to experience one this intense.

A low pressure system has lower pressure at its center than the areas around it. Winds blow towards the low pressure, and the air rises in the atmosphere where they meet. A high pressure system has higher pressure at its center than the areas around it. Winds blow away from high pressure.

So what is a “wake low”? It’s a small area of low pressure that sometimes develops behind a line of thunderstorms. The wake low forms about 30-50 miles behind the storms in a spot where the air is warming up. This creates a strong contrast between the wake low and an area of high pressure located along with the storms.

A heat burst is caused when a shower or thunderstorm weakens over a layer of dry air. The air, however, continues to descend towards the surface due to the momentum it has already acquired. As dry air descends through the atmosphere compression due to increasing atmospheric pressure causes the air to warm.

Multicell storms may produce hail, strong winds, brief tornadoes, and/or flooding. A squall line is a group of storms arranged in a line, often accompanied by “squalls” of high wind and heavy rain. Squall lines tend to pass quickly and are less prone to produce tornadoes than are supercells.

A derecho (pronounced similar to “deh-REY-cho” in English, or pronounced phonetically as ” “) is a widespread, long-lived wind storm associated with a band of rapidly moving showers or thunderstorms variously known as a squall line, bow echo, or quasi-linear convective system.

This theory proposed that the main inflow into a cyclone was concentrated along two lines of convergence, one ahead of the low and another trailing behind the low. The trailing convergence zone was referred to as the squall line or cold front.

The different types of storms are hailstorms, ice storms, snowstorms, thunderstorms, wind storms, hurricanes, and tornadoes.

Types of storms

• Blizzards.
• Hail.
• Heavy rain.
• Ice storms.
• Lightning.
• Thunderstorms.
• Wind.

A very strong wind is called storm.