The Knuckleball Problem

Presented by: Patrick Figaro Lino Gutierrez Jacob Hedden Lan Nguyen

Introduction Important topics related to explaining the knuckleball Turbulent flow vs. Laminar Flow Reynold’s Number Friction Factor and Drag force

Problem Statement A knuckleball is a type of baseball pitch that is thrown without any spin on the ball. The seams cause flow transitions over the spherical surface so that the baseball (diameter D=3 in) moves in an unpredictable manner in response to varying drag and lift. If the best speed to throw a knuckleball is about 85 mph, determine the Reynold’s number for transition. Compare your value to the data in chapter 9

Solution Given: v= 85 mph D= 3 in 85 mph 3 in.

Find: Assumptions: Plan: The Reynold’s number T=80°F P=1 atm rAir= .0735 lbm/ft3 Plan: Use Fig 3.4.3 to find viscosity Then use Re= (rvD)/m

Solution: Unit Conversions

From Fig 3.4.3

For a sphere,

Discussion: