Objects in fluids have forces and motions {fluid dynamics}|.
thrust
Forward force {thrust, fluid} pushes objects through fluid.
drag
Friction {drag} retards moving objects in fluid. Drag rises as velocity increases.
velocity
If thrust stays constant, velocity rises and drag increases, until force balance makes no more acceleration, at terminal velocity. Example is feather falling through air under gravity.
energies
At pipe points, energies are kinetic energy from fluid flow, potential energy from liquid standing in open pipes, and/or energy from outside forces and pressures. Pipe fluids have energy conservation, by Bernoulli's theorem. For streamline flow, sum of pressure P and kinetic energy KE per volume V is constant: P + (KE / V) = constant. P * V = PE, so (PE / V) + (KE / V) = KE + PE = constant total energy.
pressure
Outside force can exert pressure on fluid. Force moves fluid small distance, and kinetic energy distributes throughout fluid, increasing fluid pressure. Outside pressure P is kinetic energy per volume and is force F times distance s divided by volume V: P = KE / V = (F * s) / V.
depth
At fluid depth, gravity causes pressure. Stationary pressure P is potential energy per volume and is density d times gravity acceleration g times depth h: P = PE / V = (m*g*h) / V = (m/V) * g * h = d * g * h.
flow
Fluid flow causes kinetic energy, which exerts pressure in flow direction. Directed pressure P is kinetic energy divided by volume and is half density d times velocity v squared: P = KE / V = (0.5 * m * v^2) / V = 0.5 * (m/V) * v^2 = 0.5 * d * v^2.
Physical Sciences>Physics>Dynamics>Fluid
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Date Modified: 2022.0224