Gliding is the simplest form of animal flight, and soaring is a special form of gliding. [1]
"Gliding is powered by Gravity"
gravity-powered flight where the movement of the glider always has a downward tilt. [1]
https://eaglepubs.erau.edu/introductiontoaerospaceflightvehicles/chapter/climbing-ceiling-gliding/
The resultant aerodynamic force (R) must balance the weight (W).
For achieve this balance, the direction of motion (freestream direction) must be tilted by the glide angle with respect to the horizontal reference.
Since the glide angle is determined by the L:D ratio, L:D ratio is the key parameter of gliding. L:D ratio equals <horizontal distance>:<vertical distance> covered during a given time.
Smaller size of a flyer leads to lower Re and lower L:D ratio in general. Check out the relevant link by clicking the button on the right.
For L:D ratio < 2. gliding is only slightly better than falling. [1]
Ascending without flapping wings using energy in the atmosphere (rising air currents etc.).
Ex) vulture, albatross, eagle, stork, hawks
Ex) sailplane
The usual trick is to find air that is rising as fast or faster than the glider's sinking speed. [1]
Static Soaring
using Updraft
Dynamic Soaring
Thermal
Continuous Chimney
Discrete Ring Thermal
Ridge Lift (Slope Lift)
Hawk Ridge, Minnesota, US
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Using the boundary layer formed over the ocean surface.
Fly in with momentum --> Soar up facing wind --> at the top of the BL, turn away and glide down riding the wind --> Fly in again with the gained momentum --> ...
high wing loading is beneficial for dynamic soaring, where penetrating the wind with some momentum is required.
low wing loading is beneficial for thermal soaring, where the body gets to be "floated" and resulting low speed is advantageous to stay in circular track inside the narrow thermal.