This course includes a review of the Manning equation, along with presentation of equations for calculating the cross-sectional area, wetted perimeter, and hydraulic radius for flow of a specified depth in a pipe of known diameter. The Manning equation can be used for uniform flow in a pipe, but the Manning roughness coefficient needs to be considered variable, dependent upon the depth of flow. Equations are also given for calculating the Manning roughness coefficient, n, for a given depth of flow in a pipe of known diameter. Numerous worked examples illustrate the use of these equations together with the Manning equation for partially full pipe flow. A sample spreadsheet for making partially full pipe flow calculations is included with this course and its use is discussed and illustrated through worked examples.

Topics: Following the completion of this course, the student will be able to: calculate the cross-sectional area of flow, wetted perimeter, and hydraulic radius for less than half full flow at a given depth in a pipe of given diameter. calculate the cross-sectional area of flow, wetted perimeter, and hydraulic radius for more than half full flow at a given depth in a pipe of given diameter. use Figure 3 in the course material to determine the flow rate at a given depth of flow in a pipe of known diameter if the full pipe flow rate is known or can be calculated. use Figure 3 the course material to determine the average water velocity at a given depth of flow in a pipe of known diameter if the full pipe average velocity is known or can be calculated. calculate the Manning roughness coefficient for a given depth of flow in a pipe of known diameter, with a known Manning roughness coefficient for full pipe flow. use the Manning equation to calculate the flow rate and average velocity for flow at a specified depth in a pipe of specified diameter, with known pipe slope and full pipe Manning roughness coefficient. calculate the normal depth for a specified flow rate of water through a pipe of known diameter, slope, and full pipe Manning roughness coefficient. carry out the calculations in the above learning objectives using either U.S. units or S.I. units. use the spreadsheet included with this course to make partially full pipe flow calculations.

Note from Author: After completing this course you will have knowledge about the equations for calculating area, wetted perimeter, and hydraulic radius for partially full pipe flow and equations for calculating the Manning roughness coefficient at a given depth to diameter ratio, with a known value of the Manning roughness coefficient for full pipe flow. Practice in the use of the Manning equation for a variety of partially full pipe flow calculations will be gained through several worked examples. 

Intended Audience: for hydrologists, civil engineers, hydraulic engineers, highway engineers, environmental engineers and mechanical engineers.

Publication Source: Harlan H. Bengtson, PhD, PE