# Laminar Flow Past a 90° T-Junction

In this application, AcuSolve is used to simulate laminar flow through a channel with two outlets forming a T-junction. AcuSolve results are compared with experimental results adapted from Hayes and others (1989). The close agreement of AcuSolve results with experimental results validates the ability of AcuSolve to model cases with multiple outlet paths.

## Problem Description

The problem consists of air flowing past a T-junction in a channel, as shown in the following image, which is not drawn to scale. Air enters the channel with an average velocity of 0.667 m/s and travels past the T-junction 2.0 m from the inlet. A portion of the flow will travel out of the branch of the channel due to the pressure difference between the bulk flow and the outlet of the branch.

## AcuSolve Results

The AcuSolve solution converged to a steady state and the results reflect the mean flow conditions. As the air flows past the junction, a portion of it is diverted into the branch. A small recirculation region develops at the top of the junction and collapses before the flow exits the domain through the right branch.
The experimental value for the fraction of flow exiting the top branch of the channel is presented with the corresponding AcuSolve result in the following table.
Table 1.
Experimental fractional flow AcuSolve fractional flow Percent deviation from experimental
Fractional flow exiting the upper branch 0.887 0.883 0.451

## Summary

The AcuSolve solution compares well with experimental results for flow past a T-junction. In this application, flow is driven by a fixed flow rate at the inlet to the main branch. A portion of the flow from the main branch is diverted into the right branch of the T-junction, giving rise to recirculation just downstream of the junction. This recirculation collapses before the flow exits the side branch. The AcuSolve result for fractional flow exiting the top branch is within 0.451 percent of the experimental results.

## Simulation Settings for Laminar Flow Past a 90° T-Junction

AcuConsole database file: <your working directory>\T_junction_laminar\T_junction_laminar.acs

Global

• Problem Description
• Analysis type - Steady State
• Turbulence equation - Laminar
• Auto Solution Strategy
• Relaxation factor - 0.2
• Material Model
• Air
• Type - Constant
• Density - 1.0 kg/m3
• Viscosity - 0.003333 kg/m-sec

Model

• Volumes
• Fluid
• Element Set
• Material model - Air
• Surfaces
• Inflow
• Simple Boundary Condition
• Type - Inflow
• Inflow type - Average Velocity
• Average velocity - 0.6667 m/sec
• Max_Z
• Simple Boundary Condition - (disabled to allow for periodic conditions to be set)
• Min_Z
• Simple Boundary Condition - (disabled to allow for periodic conditions to be set)
• Outflow
• Simple Boundary Condition
• Type - Outflow
• T_Out
• Simple Boundary Condition
• Type - Outflow
• Walls
• Simple Boundary Condition
• Type - Wall
• Periodics
• Periodic 1
• Periodic Boundary Condition
• Type - Periodic

## References

R. E. Hayes, K. Nandkumar, and H. Nasr-El-Din. "Steady Laminar Flow in a 90 Degree Planar Branch". Computers and Fluids 17(4): 537-553. 1989.