184
P. Liu
Fig. 3.11 Long distance oil pipeline
3.2.8 Flow Induced Vibration (Hydroelastic Problem)
When the liquid flows through the solid side wall, it can cause the vibration
of the side wall under some conditions, which in turn, changes the flow characteristics. The theory of the interaction between liquid, water, and solid is
called hydroelastic theory.
3.3 One-Dimensional Flow Theory
and Mechanical Energy Loss
3.3.1 Theory of One-Dimensional Flow
In hydraulics, if the flow coordinates s and time t are taken as independent variables, the hydraulic elements such as velocity and pressure can be
expressed as (s, t) functions, thus the so-called one-dimensional flow theory
is proposed. If a microelement area dA perpendicular to the streamline is
taken in the flow field, a microelement flow tube can be formed through
the perimeter of the microelement surface as the streamline, as shown in
Fig. 3.12. A beam of liquid filled with a microchannel is called a beam.
According to the principle that streamline cannot intersect, the flow in the
microelement flow tube will not flow outward through the flow tube wall,
and the flow outside the flow tube will not flow inward through the flow tube
wall. When the liquid flow is constant, the shape and position of the micro
flow tube do not change with time. However, in the case of unsteady flow,
P. Liu
Fig. 3.11 Long distance oil pipeline
3.2.8 Flow Induced Vibration (Hydroelastic Problem)
When the liquid flows through the solid side wall, it can cause the vibration
of the side wall under some conditions, which in turn, changes the flow characteristics. The theory of the interaction between liquid, water, and solid is
called hydroelastic theory.
3.3 One-Dimensional Flow Theory
and Mechanical Energy Loss
3.3.1 Theory of One-Dimensional Flow
In hydraulics, if the flow coordinates s and time t are taken as independent variables, the hydraulic elements such as velocity and pressure can be
expressed as (s, t) functions, thus the so-called one-dimensional flow theory
is proposed. If a microelement area dA perpendicular to the streamline is
taken in the flow field, a microelement flow tube can be formed through
the perimeter of the microelement surface as the streamline, as shown in
Fig. 3.12. A beam of liquid filled with a microchannel is called a beam.
According to the principle that streamline cannot intersect, the flow in the
microelement flow tube will not flow outward through the flow tube wall,
and the flow outside the flow tube will not flow inward through the flow tube
wall. When the liquid flow is constant, the shape and position of the micro
flow tube do not change with time. However, in the case of unsteady flow,