Fluid Mechanics

08/04/26 Wed 11:38am

$$\tau \propto \frac{du}{dy}$$

shear stress is directly proportional to strain rate

$$\tau =\mu \frac{du}{dy}$$

where $\mu$ is

Fluid

• Laminar
• Turbulent

$$R_e<2000\text{ Laminar}$$ $$R_e>4000\text{ Turbulent}$$ $$R_e=\frac{\rho Vd}{\mu }\approx \frac{Vd}{\frac{\rho }{\mu }}\approx \frac{Vd}{\vartheta }$$

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forcce on elemental area is

$$F=\tau \times 2\pi r\times dx$$