Hydraulics/Fluid Mechanics a.y. 2020-2021
PIPE FLOWS : LOCAL HEAD LOSSES
Prof. Stefania Espa
DICEA-SAPIENZA UNIVERSITY OF ROME
CIVIL AND INDUSTRIAL ENGINEERING
BATCHELOR IN SUSTAINABLE BUILDING ENGINEERING
RIETI
All images uploaded are for educational purposes
, PIPE FLOWS - LOCAL (MINOR) HEAD LOSSES: Introduction
In pipe systems we need usually to consider devices as valves and/or change in
geometry/direction like (sudden) enlargements, contractions, inlets,
outlets, bends. All these situations cause local (concentrated) head losses,
referred to as minor losses.
Why ? Each of these elements causes a change in the magnitude and/or the
direction of the velocity vectors and hence results in a loss. In general, if the
flow is gradually accelerated by an element, the losses are very small;
relatively large losses are associated with sudden enlargements or
contractions because of the separated regions that result (a separated flow
occurs when the primary flow separates from the wall)
These losses are usually evaluated as a function of the kinetic head hL=KV2/2g;
where values of K have been determined experimentally for the various
fittings and geometry changes of interest in piping systems (examples). When
the pipe is ‘long’ enough (need to be defined!) this losses can be neglected.
PIPE FLOWS : LOCAL HEAD LOSSES
Prof. Stefania Espa
DICEA-SAPIENZA UNIVERSITY OF ROME
CIVIL AND INDUSTRIAL ENGINEERING
BATCHELOR IN SUSTAINABLE BUILDING ENGINEERING
RIETI
All images uploaded are for educational purposes
, PIPE FLOWS - LOCAL (MINOR) HEAD LOSSES: Introduction
In pipe systems we need usually to consider devices as valves and/or change in
geometry/direction like (sudden) enlargements, contractions, inlets,
outlets, bends. All these situations cause local (concentrated) head losses,
referred to as minor losses.
Why ? Each of these elements causes a change in the magnitude and/or the
direction of the velocity vectors and hence results in a loss. In general, if the
flow is gradually accelerated by an element, the losses are very small;
relatively large losses are associated with sudden enlargements or
contractions because of the separated regions that result (a separated flow
occurs when the primary flow separates from the wall)
These losses are usually evaluated as a function of the kinetic head hL=KV2/2g;
where values of K have been determined experimentally for the various
fittings and geometry changes of interest in piping systems (examples). When
the pipe is ‘long’ enough (need to be defined!) this losses can be neglected.
