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The coefficient of drag for a sphere in Stokes' law quantifies the drag or resistance experienced by a sphere moving through a fluid at low Reynolds numbers (Re < 0.2). This simplified formula applies to creeping flow conditions where viscous forces dominate.
The calculator uses the Stokes' law equation:
Where:
Explanation: This formula applies specifically to spherical objects in laminar flow conditions where inertial forces are negligible compared to viscous forces.
Details: Calculating the drag coefficient is essential for understanding fluid resistance on spherical objects, designing particle separation systems, analyzing sedimentation rates, and studying microscopic particle behavior in fluids.
Tips: Enter the Reynolds number (must be greater than 0). The calculator is valid for Reynolds numbers less than 0.2, where Stokes' law applies accurately.
Q1: Why is this formula limited to Re < 0.2?
A: For Reynolds numbers above 0.2, inertial effects become significant and the simple Stokes' law relationship no longer accurately describes the drag behavior.
Q2: What are typical applications of this formula?
A: This formula is commonly used in aerosol science, sedimentation analysis, microfluidics, and studying the motion of small particles in viscous fluids.
Q3: How does sphere size affect the drag coefficient?
A: For a given Reynolds number, the drag coefficient remains constant regardless of sphere size, as the relationship is purely dependent on the flow characteristics.
Q4: What happens at higher Reynolds numbers?
A: At higher Reynolds numbers, more complex drag coefficient formulas are needed that account for both viscous and inertial effects on the flow around the sphere.
Q5: Can this formula be used for non-spherical objects?
A: No, this specific formula applies only to perfect spheres. Non-spherical objects have different drag coefficient relationships.