Fluid Flow Analysis

Application Overview:

• See Fluid Flow Analysis Setup for details on user input options for this application.  

• For general details on running an application, selecting and displaying output variables, see Running DEW Applications.  

• The Available Output Variables for the application are described in the last section of this topic.

Fluid Flow is the core application for the DEW hydraulic model solution.  Hydraulic modeling capabilities are incorporated in DEW to create interdependent system analyses that offers increased levels of details, enhancing design simulation and operational response capabilities for:

• Emergency Management

• Mission Prioritization

• Readiness Deployment

DEW provides the standard features commonly found in hydraulic modeling applications:

• Choice of Darcy-Weisbach, Hazen-Williams, or Manning calculations for pipe headloss.

• Supports multiple time-dependent nodal fluid loads (demands)

• Supports pressure-dependent flow demands

• Models common valves & fittings

• Supports constant and variable speed pumps and allows tracking of pump energy/costs

• Supports simple and rules-based tank operations, i.e. empty/fill cycles.

• Supports irregular shaped storage tanks, allowing user input of tank curves

Application Run / Results:

See Running DEW Applications for general details on running the application, selecting and displaying output variables.

• Fluid Flow calculates Pressures and Flows throughout the distribution network for the selected time point.

• If more than one time point is selected, the Fluid Flow results apply to the earliest time point selected.  

• If no time points are selected, Fluid Flow runs for the first time point.
   

• Fluid Flow may be set to run with Hazen-Williams, Darcy-Weisbach, or Manning pipe headloss calculations.
   

Hazen-Williams:

• Empirical pressure drop calculation relating (per unit length) pipe headloss to flow, pipe diameter, and the Hazen-Williams pipe coefficient (i.e. C-factor).

• Commonly used for water distribution, fire sprinkler, and irrigation systems.  

• Relatively accurate for water at temperatures from 40-75oF under turbulent flow conditions (Reynolds#>105)

• Not valid for hot water systems or for those using other working fluids.

Darcy-Weisbach:

• Theoretically based calculation relating (per unit length) pipe headloss to flow, pipe diameter, and the Darcy friction factor, which is dependent on pipe roughness and Reynolds number.

• Valid for all fully-developed, steady-state, and incompressible fluid flow systems for any known temperature, as viscosity and flow characteristics are incorporated into the friction factor determination.  

• The standard application utilizes the Swamee-Jain approximation for the Darcy friction factor calculation.   

Manning:

• Empirical pressure drop calculation relating (per unit length) pipe headloss to flow, hydraulic radius, and the Manning roughness coefficient.  

• Most commonly used for gravity-driven, open-channel flows.  

Fluid Flow results are developed from various user-specified sources:

• Customer demands (i.e. entered fluid loads) define flow rates leaving the network

• Tank levels and resultant hydraulic grade determine whether tank is at steady state, emptying, or filling

• Pumps define the operating pressure at specific locations in the system

• Control Valve settings define set operating pressures or flows at specific points in system

• Load scaling modifies defined loading by defined scale factor, either entered directly or calculated from actual measurement data.  

Displayed results can be color-coded into the drawing using variable range display to indicate:

• Hydraulic Grade Line regions (or pressure zones)

• Volumetric or Mass Flow Rates

• Pipe Velocities

• Pipe Sizes

The Fluid Flow application can also flag user-specified equipment and system operating limit violations.  

• Fluid Flow flags violations of user-defined operating pressure limits (low or high) by attaching a message to the out-of-range components.

• Fluid Flow also flags high-velocity regions, with messages attached to pipes where the average fluid velocity exceeds the user-defined limit.  

For details regarding any other specific component interactions related to this application, see component of interest in the Component Library.  

Available Output Variables:

For general details on running an application, selecting and displaying output variables, see Running DEW Applications.  The output variables available for display from the Fluid Flow application are described in the following table.