Fluids
Opposition to movement is a multi-fold process. The surfaces of encounter between the swimmer and the fluid provide resistance to efficient motion. Energy is sucked off as fluids change from laminar to turbulent flow. Flow may also become diverted inward creating rotations called vortices that project downstream from the swimmer.Drag depends on inertia (the tendency to stay put). Inertia is proportional to mass. Fluid density or mass per unit volume is the important factor for our discussion.Drag comes in two important varieties. Form drag is determined by shape. Friction drag is determined by the nature of the surface. Friction is discussed in terms of viscosity or how readily one layer slips past another.An important concept in the study of aerodynamics conce
In fact, molecules are in constant random motion. Air molecules travel faster over the top to meet molecules moving underneath at the trailing edge. The figure shows the computed streamlines around an airfoil. The part of the theory about Bernoulli's equation and a difference in pressure existing across the airfoil is correct. The faster the movement, the thinner the stationary layer. It is easiest to visualize a streamline if we move along with the body (as opposed to moving with the flow). Why should they? Molecules have no "knowledge" of their neighbors - they're inanimate. Large and small swimmers experience very difference dynamic environments in the same fluid. Since the streamline is traced out by a moving particle, at every point along the path the velocity is tangent to the path. Measured flows traveling over the top of a lifting airfoil do move faster than those going underneath. Since no mass passes through the surface of the airfoil (or cylinder), the surface of the object is a streamline. A streamline is a path traced out by a massless particle as it moves with the flow. The flow proceeds from left to right. But they travel much faster than the speed required to have the molecules meet up at the back end.
Common topics in this essay:
,
stationary layer,
molecules near,
thickness stationary layer,
thickness stationary,
thinner stationary layer,
speed faster,
meet molecules,
drag determined,
shape friction,
trailing edge,
thinner stationary,
travel faster,
|
Acceptance Essays
