👉 The entrance fluid, also known as the entrainment fluid, is a layer of air that surrounds and flows over an object moving through a fluid, such as water or air. This fluid layer forms due to the difference in velocity between the object and the surrounding fluid, creating a boundary layer where the fluid gradually transitions from the object's surface to the free stream. The entrance fluid plays a crucial role in reducing turbulence and drag by smoothing out flow separation, especially at the leading edge of the object. It acts as a buffer, allowing for a more gradual change in flow direction and minimizing abrupt transitions that can cause significant resistance.
