Unit 35: Turbulent Flow & Reynold’s Number
Practice Problems
Note: problem difficulty is ranked using a star system.
(*) One-star problems are fundamental to the unit, and can be done relatively quickly. Use these problems to introduce yourself to the material.
(**) Two-star problems are more difficult, and require an understanding of one or two key concepts. Use these problems to test your understanding of the material.
(***) Three-star problems are the most difficult, and require some creative thinking in addition to a deep familiarity with multiple key concepts. Use these problems to challenge yourself; if you can complete one of these, you’re on your way to mastering the material.
*Q35.1) Calculate the Reynold’s number of water flowing through a pipe of radius 1cm at an average speed of 10 m/s. Would the water be turbulent?
**Q35.2) Find the maximum speed at which water can flow through a pipe of radius 2cm while maintaining lamenar (aka streamline) flow.
**Q35.3) Find the maximum flow rate at which sap can flow through a spout of diameter 1cm while maintaining lamenar (aka streamline) flow. Sap has a viscosity five times that of water and a specific gravity of 1.2.
***Q35.4) Consider the tapering pipe shown below, with its narrow end having one sixth the cross-sectional area of its wider end.
a) If a fluid were to flow through this pipe, what would be the ratio of the fluid’s Reynold’s number at the narrow end to that of the wide end?
b) At which end would the fluid have the higher likelihood of being turbulent?