This section details CFD simulations on multi-element thin airfoils. This would be applicable to personal gliders that utilize wings made of thin cloth or nylon material, such as wing suits and the Kitewing.
The Kitewing is very interesting to me because it is a personal (passive) lift surface. It is designed to be used as a land sail for use with skiing, skateboarding, and other forms of personal land locomotion.
The wing suit is essentially parachute material worn over the body to turn the body into a wing. I have not seen much of it in practical use, but it is popular with extreme sports athletes.
A typically cited practical glide ratio is 2:1. This means for every 1 unit of length the body falls, the body goes forward 2 units of length. As the ratio increases, steady level flight (i.e. real flight) is approached. Of course, steady level flight cannot be achieved until a source of power is present to overcome the power consumed by drag.
Let's analyze a wing suit descent with a free body diagram.
In a steady (constant velocity, non-accelerating) descent, gravitational energy is converted to kinetic energy to overcome drag. The free-body diagram below can be made.
Remember that lift and drag are always normal and parallel forces with the freestream, respectively. It is not a totally arbitrary rule, but grounded in the physics of of how wings work, i.e. the deflection of oncoming air.
If we tilt the whole diagram so that flight velocity is horizontal, we see that gravity becomes a thrust in the new transformed diagram. For a steady descent, the gravitational force balances out the drag and lift.
The Kitewing is very interesting to me because it is a personal (passive) lift surface. It is designed to be used as a land sail for use with skiing, skateboarding, and other forms of personal land locomotion.
The wing suit is essentially parachute material worn over the body to turn the body into a wing. I have not seen much of it in practical use, but it is popular with extreme sports athletes.
A typically cited practical glide ratio is 2:1. This means for every 1 unit of length the body falls, the body goes forward 2 units of length. As the ratio increases, steady level flight (i.e. real flight) is approached. Of course, steady level flight cannot be achieved until a source of power is present to overcome the power consumed by drag.
Let's analyze a wing suit descent with a free body diagram.
In a steady (constant velocity, non-accelerating) descent, gravitational energy is converted to kinetic energy to overcome drag. The free-body diagram below can be made.
Remember that lift and drag are always normal and parallel forces with the freestream, respectively. It is not a totally arbitrary rule, but grounded in the physics of of how wings work, i.e. the deflection of oncoming air.
If we tilt the whole diagram so that flight velocity is horizontal, we see that gravity becomes a thrust in the new transformed diagram. For a steady descent, the gravitational force balances out the drag and lift.
Let's define the following symbols.
Then we can get the following trigonometric and aerodynamic equations.
For steady descent, the following conclusion can be drawn.
So we see that the lift-to-drag ratio of the wing suit will determine the glide ratio in a steady descent. This is a result commonly derived for a gliding plane.