# Presentation: 372576

## Improving Contaminant Mixing Models For Water Distribution Pipe Networks

**Improving Contaminant Mixing Models For Water Distribution Pipe Networks**

**Siri Sahib S. Khalsa**
**University of Virginia**
**Charlottesville, VA**
**khalsa@virginia.edu**

**Clifford K. Ho**
**Sandia National Laboratories**
**Albuquerque, NM**
**ckho@sandia.gov**

**Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under Contract DE-AC04-94AL85000.**

**Problem**

**Development of New Mixing Model**

**Objective:** Predict concentrations resulting from two pipe flows intersecting at a junction

**Objective and Approach**

**   ****Implementation and Data Testing**

**Ongoing Research**

**Conclusions**

- Mixing in a cross junction is incomplete and physically bounded by predictions of the complete-mixing and bulk-mixing models
- Our new models have been implemented into EPANET, and results show significant improvement in contaminant transport predictions

- Employ computational fluid dynamics software to study contaminant mixing in cross junctions, develop a new mixing model, and implement it into EPANET

- Understanding and predicting solute transport through water distribution pipe networks are important to mitigate potential contamination events

- Much of the water distribution industry relies on the Environmental Protection Agency’s water quality simulation software (EPANET)

- However, EPANET incorrectly assumes contaminants mix instantaneously and completely in junctions, leading to potentially inaccurate transport predictions

- Use laboratory data to test and improve our new mixing model

**   ****Flow Simulation**

- 3-D simulations with computational fluid dynamics software reveal incomplete mixing within junctions, contrary to the assumption of the current mixing model

- Equal Flow Rates

- Unequal Flow Rates

- Bulk fluid momentum is retained in the mixing process
- Our new mixing model honors bulk advective transport as a lower bound to the amount of mixing in a junction
- A mixing parameter is used to scale the results between the complete-mixing and bulk-mixing model predictions

- Tracer Inlet

- Clean Inlet

- Tracer Inlet

- Clean Inlet

- The new mixing model was implemented into EPANET and used to predict contaminant concentrations at various sensor locations in laboratory pipe networks

**3x3 Network: Tracer Inlet Flow Rate > Clean Inlet Flow Rate**

**New Mixing Model Solution**

**Original EPANET Solution**

**Original EPANET Solution**

**New Mixing Model Solution**

**3x3 Network: Clean Inlet Flow Rate > Tracer Inlet Flow Rate**

- Predictions by EPANET implemented with the new mixing model agree with laboratory measurements when appropriate mixing parameters are used

**Sensor**

**Sensor Concentrations in 3x3 Network**

**Sensor**

**Normalized Concentration**

**Sensor Concentrations in 3x3 Network**

**Clean Inlet Flow Rate > Tracer Inlet Flow Rate**

- Analysis of mixing behavior in other pipe-junction configurations

- U Junction

- Double-T Junction

- Inverse modeling to calibrate combined mixing model to pipe-network data

- Development of mixing parameter regressions as functions of different flow conditions

- Working with the Environmental Protection Agency to implement and distribute our new models

- ContaminatedWater

- Clean Water

- Validation of combined mixing model using both large-scale and laboratory pipe-network data

**Normalized Concentration**

**Tracer Inlet Flow Rate > Clean Inlet Flow Rate**