Velocity Gradient (Mixing)
Calculate the mean velocity gradient (G) in rapid-mix and flocculation chambers, G = √(P ÷ (μ × V)), from the dissipated power (W), the water dynamic viscosity (Pa·s) and the chamber volume (m³). The result, in s⁻¹, measures mixing intensity: rapid mixing needs high G (700–1000 s⁻¹) to disperse the coagulant, while flocculation uses low G (20–70 s⁻¹) to promote floc collision and growth without breaking them. Enter power, viscosity and volume.
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Gradiente de velocidade (mistura)
Na coagulação-floculação, a intensidade da agitação é tão importante quanto a dose de produto químico, e ela é medida pelo gradiente de velocidade médio G, definido por Camp e Stein como G = √(P ÷ (μ × V)): a raiz quadrada da potência dissipada P (W) dividida pela viscosidade dinâmica da água μ (Pa·s) vezes o volume da câmara V (m³). O resultado, em s⁻¹, descreve o quanto camadas vizinhas de água deslizam umas sobre as outras. As duas etapas pedem regimes opostos: a mistura rápida precisa de G alto (700–1000 s⁻¹), uma agitação violenta e curta para dispersar instantaneamente o coagulante e desestabilizar as partículas coloidais; já a floculação precisa de G baixo (20–70 s⁻¹), uma agitação suave e prolongada que promove a colisão e o crescimento dos flocos sem rompê-los — flocos grandes e densos decantam melhor. O produto G·t (gradiente × tempo) também é usado como critério de projeto. Informe a potência, a viscosidade e o volume da câmara.
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