The wetted perimeter is the perimeter of the cross sectional area that is "wet." The term wetted perimeter is common in Civil Engineering

Civil engineering

Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including works like roads, bridges, canals, dams, and buildings...

, Environmental Engineering

Environmental engineering

Environmental engineering is the application of science and engineering principles to improve the natural environment , to provide healthy water, air, and land for human habitation and for other organisms, and to remediate polluted sites...

 and heat transfer

Heat transfer

Heat transfer is a discipline of thermal engineering that concerns the exchange of thermal energy from one physical system to another. Heat transfer is classified into various mechanisms, such as heat conduction, convection, thermal radiation, and phase-change transfer...

 applications; it is associated with the hydraulic diameter. Engineers commonly cite the cross sectional area of a river.

This can be defined mathematically:


Where is the length of each surface in contact with the aqueous body.

In open channel flow

Open channel flow

Open-Channel Flow, a branch of Hydraulics, is a type of liquid flow within a conduit with a free surface, known as a channel. The other type of flow within a conduit is pipe flow. These two types of flow are similar in many ways, but differ in one important respect; the free surface...

, the wetted perimeter is defined as the surface of the channel bottom and sides in direct contact with the aqueous body. Friction

Friction

Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...

 losses typically increase with an increasing wetted perimeter, resulting in a decrease in heat. In a practical experiment, one is able to measure the wetted perimeter with a tape measure weighted down to the river bed to get a more accurate measurement

Measurement

Measurement is the process or the result of determining the ratio of a physical quantity, such as a length, time, temperature etc., to a unit of measurement, such as the metre, second or degree Celsius...

.

See also

• Hydrological transport model
  Hydrological transport model
  An hydrological transport model is a mathematical model used to simulate river or stream flow and calculate water quality parameters. These models generally came into use in the 1960s and 1970s when demand for numerical forecasting of water quality was driven by environmental legislation, and at...
  
  
• Manning formula
  Manning formula
  The Manning formula, known also as the Gauckler–Manning formula, or Gauckler–Manning–Strickler formula in Europe, is an empirical formula for open channel flow, or free-surface flow driven by gravity...
  
  
• Hydraulic radius