What is the difference between subcritical and supercritical flow?

Subcritical flow is dominated by gravitational forces and behaves in a slow or stable way. It is defined as having a Froude number less than one. Supercritical flow is dominated by inertial forces and behaves as rapid or unstable flow.

What is control section in open channel flow?

In open channel flow control section is a section where for a given discharge the depth of flow is known or it can be controlled. So the control section for subcritical flow will be at downstream location and the control section for supercritical flow will be at the upstream location.

What is control section?

[kən′trōl ‚sek·shən] (computer science) The smallest integral subsection of a program, that is, the smallest unit of code that can be separately relocated during loading. The part of a central processing unit that controls other sections of the unit.

Why an elementary wave can move upstream in subcritical flow?

In subcritical flow a disturbance travelling at a celerity C can move upstream and downstream because the wave celerity C is larger than the flow velocity V (i.e. V/C<1). All rapid flows are controlled by the upstream flow conditions.

What is the meaning of subcritical?

Definition of subcritical 1 : less or lower than critical in respect to a specified factor. 2a : of insufficient size to sustain a chain reaction a subcritical mass of fissionable material.

Why trapezoidal section is most economical?

The most economical section of a trapezoidal channel is one which has hydraulic mean depth equal to half the depth of flow. The discharge through a channel of trapezoidal section is maximum when the sloping side is equal to half the width at the top.

What is the difference between open channel flow and pipe flow?

Open Channel Flow is a type of fluid flow in a conduit with a free surface open to the atmosphere. The pipe flow is a type of flow within a closed conduit. The maximum velocity occurs at the center of the pipe. HGL(Hydraulic Gradient Line ) coincides with the water surface line.

What is gradually varied flow?

Gradually Varied Flow. ○ In this section we consider gradually varied. flow (GVF), which is a form of steady. nonuniform flow characterized by gradual variations in flow depth and velocity (small slopes and no abrupt changes) and a free surface that always remains smooth (no discontinuities or zigzags).

When the depth of flow remain same at every section along the open channel is said to be a?

Figure 5-5. A uniform open-channel flow: the depth and the velocity profile is the same at all sections along the flow.

Why do hydraulic jumps occur?

A hydraulic jump occurs when the upstream flow is supercritical (F>1). To have a jump, there must be a flow impediment downstream. Water depth increases during a hydraulic jump and energy is dissipated as turbulence. Often, engineers will purposely install impediments in channels in order to force jumps to occur.

What is subcritical fluid?

Subcritical water is liquid water under pressure at temperatures above usual boiling point, 100 °C (212 °F). It is also known as “subcritical water” or “pressurized hot water.” At subcritical state, water is maintained in liquid form by apply pressure.

What is the control section for a subcritical flow?

So control section for subcritical flow is at downstream location. In a Subcritical flow the disturbance can travel upstream side, hence the u/s condition can change. So the downstream section will act as a control section. In a Suupercritical flow the disturbance cannot travel upstream side ,hence the u/s condition cannot change.

Can a disturbance travel upstream in a supercritical flow?

Conversely, a disturbance cannot travel upstream in a supercritical flow because the celerity is less than the flow velocity (i.e. V/C > 1). Hence supercritical flows can only be controlled from upstream (i.e. upstream flow control ). All rapid flows are controlled by the upstream flow conditions.

How do comcomputations proceed from upstream to downstream?

Computations must proceed at the same time from the upstream end (supercritical flow) and from the downstream end (subcritical flow). Near the break in grade, there is a transition from a supercritical flow to a sub-critical flow.

What is the difference between downstream and upstream flow control?

This is called a downstream flow control. Conversely, a disturbance cannot travel upstream in a supercritical flow because the celerity is less than the flow velocity (i.e. V/C > 1). Hence supercritical flows can only be controlled from upstream (i.e. upstream flow control ).