F ASES Y N IVELES DE A CTIVACIÓN

The Gradually Varied Flow tab comprises an input section on the left and an output, or results, section on the right. There is also a Direction drop-down list:

• Direction—This drop-down list lets you choose whether you are solving for the

Upstream Depth or the Downstream Depth, as follows:

– Given Upstream—When you choose this option, the Upstream Depth is an

input variable and the gradually varied flow analysis will solve for down- stream depth.

– Given Downstream—When you choose this option, the Downstream Depth

is an input variable and the gradually varied flow analysis will solve for upstream depth.

Input:

• Downstream Depth—Distance from water surface to low point of channel

bottom at the downstream end of the channel.

• Upstream Depth—Distance from water surface to low point of channel bottom at

the upstream end of the channel. • Length—The length of the channel.

• Number of Steps—The number of segments per profile that the channel is

divided into based on its starting and goal depth. In unbounded cases, the number of steps is used to determine the marching interval, but not as strictly as in a bounded profile. This input is required by the direct step method that is used in the gradually varied flow analysis. It is recommended that the value entered here be at least five for accuracy. Increasing this number will increase the accuracy of the hydraulic grade calculation, but will increase the calculation time.

Output:

• Profile Description—The profile classification within the channel.

Note: More information about the various profile types can be found in “Profile Classification” on page 5-149.

• End Depth/Rise—Distance from water surface to low point of channel bottom at

the end of the channel.

• Normal Depth/Rise—Average distance from water surface to low point of

channel bottom along the length of the channel.

• Downstream Velocity—Linear measure of flow rate at the downstream end of the

channel, given in units of length over time.

• Upstream Velocity—Linear measure of flow rate at the upstream end of the

channel, given in units of length over time.

• Channel Slope—Longitudinal slope in the channel. Also, the vertical drop

divided by the channel length.

• Discharge—Volumetric rate of flow, given in units of length (cubed) over time.

3.9

Pipe Worksheet Dialog Boxes

The available pipe worksheets are as follows: • “Pressure Pipe Dialog Box”

• “Circular Pipe Dialog Box”

• “Box Pipe Worksheet Dialog Box”

• “Elliptical Pipe Section Dialog Box”

• “Irregular Section Dialog Box”

3.9.1

Pressure Pipe Dialog Box

The Pressure Pipe worksheet dialog box comprises an input section on the left and an output, or results, section on the right.

Additionally, a Messages tab is included in each worksheet. The top section of this tab displays informational calculation messages, while the bottom section lets you enter any explanatory notes that you wish to be associated with the worksheet.

Input:

• Pressure at 1—Measured or computed pressure at section 1 in Bernoulli's Equa-

tion.

• Pressure at 2—Measured or computed pressure at section 2 in Bernoulli's Equa-

tion.

• Elevation at 1—Measured or computed elevation at section 1 in Bernoulli's

• Elevation at 2—Measured or computed elevation at section 2 in Bernoulli's

Equation.

• Length—Distance from section 1 to section 2 measured along the channel center-

line in Bernoulli's Equation.

• Roughness Coefficient—Average height of roughness particles in the channel.

• Diameter—The inside diameter of a circular channel.

• Discharge—Volumetric rate of flow, given in units of length (cubed) over time.

• Kinematic Viscosity—(This input is only available when one of the Darcy-Weis-

bach Friction methods is used)—Viscosity divided by the mass density given in units of length (squared) over time, hence the term kinematic. Viscosity is a prop- erty measuring the fluid resistance to shear. For example, molasses and tar have relatively high viscosity and water and air relatively low viscosity.

• Specific Weight—(This input is only available when one of the Darcy-Weisbach

Friction methods is used) The weight of a unit volume of a substance. Output:

• Headloss—Loss of energy grade over a longitudinal channel distance.

• Energy Grade at 1—Energy (total energy of flow with reference to a datum.

Computed for closed channels as the sum of channel centerline height above datum, piezometric height, and the velocity head. Computed for open channels as the sum of channel invert height above datum, the flow depth, and velocity head) of flow at section 1 in Bernoulli's Equation.

• Energy Grade at 2—Energy (total energy of flow with reference to a datum.

Computed for closed channels as the sum of channel centerline height above datum, piezometric height, and the velocity head. Computed for open channels as the sum of channel invert height above datum, the flow depth, and velocity head) of flow at section 2 in Bernoulli's Equation.

• Hydraulic Grade at 1—Hydraulic grade of flow at section 1 in Bernoulli's Equa-

tion.

• Hydraulic Grade at 2—Hydraulic grade of flow at section 2 in Bernoulli's Equa-

tion.

• Flow Area—Cross sectional area of flow.

• Wetted Perimeter—Perimeter of flow that travels against a solid boundary. For a

partially full pipe, the wetted perimeter includes all of the flow perimeter except for the top segment, which has a free surface.

• Velocity—Linear measure of flow rate given in units of length over time.

• Velocity Head—Energy due to the velocity of a liquid.

• Friction Slope—Slope of the energy grade line (sum of base elevation, velocity

• Friction Factor—Friction coefficient used in the Darcy-Weisbach (Colebrook-

White) Formula.

• Reynolds Number—Ratio of viscous forces relative to inertial forces.

3.9.2

Circular Pipe Dialog Box

The following controls make up the circular pipe worksheet dialog box:

• Solve For—This drop-down list lets you select the variable that you are solving

for. The variable that is chosen will appear yellow (read-only) in the list of avail- able input fields.

• Friction Method—This drop-down list lets you select the friction method that

will be used to calculate the worksheet. The Darcy-Weisbach method requires an additional input variable (Kinematic Viscosity) and generates additional output (Friction Factor and Reynolds Number).

• Messages—A Messages tab is included in each worksheet. The top section of this

tab displays informational calculation messages, while the bottom section lets you enter any explanatory notes that you wish to be associated with the worksheet. This dialog box comprises the following tabs: