# Applications

We use the new theory presented under Fluid Mechanics to explain a variety of phenomena of slighly viscous fluid flow. In particular we discover the true mechanisms of drag and lift arise in slightly viscous fluids such as air and water, and thus uncover the secrets of flying, sailing, swimming and ball sports, and the action of propellers and turbins, which are not revealed in fluid mechanics literature and education.

### Why It Is Possible to Fly

A new explanation is presented of how a wing generates large lift with small drag, based on computing turbulent solutions to the incompressible Euler equations. It is seen that the same mechanism which generates drag from low-pressure streamwise vorticity at the trailing edge, redistributes the pressure over the wing surface and thereby generates lift. It is shown that the classical explanation by Kutta-Zhukovsky is purely fictional and does not describe real physics of gliding flight.

### Why It Is Possible to Sail

We explain how the sail and keel of a sailing boat, both acting like wings, together pull/drive the boat forward in beating at 35-45 degrees against the wind. We explain the somewhat different action of a sail and a symmetric wing like a keel, with the angle of attack of a sail 15-25 degrees and of a keel 5-10 degrees. We show that classical explanations are incorrect.

### Why a Frisbee Flies so Well

We explain how the rotation of a frisbee makes the frisbee into an efficient airfoil generating substantial lift at small drag. The rotation makes the boundary layer turbulent which delays separation and thereby increases lift and reduces drag.

### Why a Propeller Gives Thrust

We explain how the blade of a rotating propeller by acting like a wing generates lift and drag with a forward axial component giving thrust at the expense of tranversal angular components of lift and drag requiring torsion of the propeller axis.

### Why Paragliding Is Possible

We explain how the flow of air around a 20 squaremeter parafoil generates enough lift to carry a man. We give evidence that classical explanations are incorrect.

### Why Phelps’ Dolphin Kick Works

We give a scientific explanation of why the Dolphin Kick of Michael Phelps is so efficient.

### Why a Helicopter Can Fly

We explain how the rotor blades of a helicopter acting like a pair wings generate lift and the expense of torsion of the rotor axis to overcome drag.

### Why Birds Can Fly

We explain gliding and flapping flight of birds based on computing turbulent solutions of the Navier-Stokes equations. We show that classical explanations are incorrect.

### Why Bumblebees Can Fly

We present a new explanation of the generation of lift during a wing stroke of flapping flight based on computing turbulent solutions of the Navier-Stokes equations at moderate to large Reynolds numbers. The new theory suggest a resolution of the enigma of why bumblebees can fly.

### How a Wind Turbine Works

We explain how the flow of air around the rotor blades of a wind turbine creates a lift force, which turns the rotor around its axis and drives a generator of electric energy.

### How a Wing Paddle Works

We explain how the motion of a wing paddle through water generates lift pulling the paddle forward-outward thus giving additional forward thrust.

### How a Boomerang Flies

We explain how the rotation of a boomerang generates non-uniform lift causing precession making it return after traveling a long distance.

### Why a Topspin Tennis Ball Curves Down

We present, based on computing turbulent solutions of the Navier-Stokes equations, a new explanation of the Magnus effect causing a topspin tennis ball to curve down and a backspin curve up. We also explain the reverse Magnus effect causing a backspin table tennis ball to curve down. We show that the classical explanation of the Magnus effect based on potential flow with circulation is non-physical and thus incorrect.

### Why Wingsuit Flying Is Possible

We explain why wingsuit flying with a lift/drag ratio of 2-3:1 is possible.

### Aerodynamics of Discus Throw

We explain how the rotation of a discus makes it into a reasonably efficient airfoil generating substantial lift at a lift/drag ratio ~ 3, thus increasing the length of the throw with 5-10 meters. The rotation makes the boundary layer turbulent which delays separation at the high angle of attack in descent.

### The Disastrous Theory of the Andree Arctic Expedition

Can you steer a balloon by drag-ropes?