Computing Mizing Elbow

Volumetric Geometry/Domain Preparation   |   Pressure based & Steady   |   Turbulence (k-omega SST)   |   Data Post-Processing

Minor Project - Mixing Elbow,
Flowthermolab
18/08/2025

Project Overview

This project presents a steady-state CFD analysis of a Mixing Elbow to investigate:

• Flow mixing behavior
• Velocity distribution
• Temperature profile
• Outlet uniformity

Problem Statement

Perform a Pressure-Based, Steady-State CFD Simulation to analyze mixing inside a pipe elbow with two inlets:

Inlet	Velocity	Temperature
Big Inlet	20 m/s	60oC
Small Inlet	30 m/s	100oC
Outlet	Pressure Outlet	-

Objective:

• Study velocity field behavior
• Analyze temperature mixing
• Evaluate outlet flow uniformity
• Suggest flow control improvements

Software Used

1.   Ansys Space-Claim ------- Geometry Cleanup and refinement
2.   Ansys Fluent Mesher ----- Mesh / Grid Generation
3.   Ansys Fluent ------------- Computation
4.   Ansys Post Processor ---- Post Processing
5.   MATLAB ------------------ Data Analysis & Scientific Plots

Methodology

1. Geometry Cleanup and refinement

• Cleaned provided geometry for computation
• Internal flow domain extracted for simulation.

Domain prepared (Mixing Elbow)

2. Mesh Details

• Surface mesh max size: 7 mm
• Curvature normal angle: 12^o
• 2 cells per gap
• First layer height: 0.00022168 mm
• Y+ ≈ 1
• 12 boundary layers (growth rate: 1.01)
• Poly-Hexcore volumetric meshFocused on mesh refinement at: Valve throat, Valve seat, and Valve lift region.
• Mesh Statistics:
  • Nodes: 142,154
  • Elements: 52,776

Meshed Domain (Number of Elements: 52776)

3. Solver Settings

Parameter	Setting
Solver Type	Pressure-Based
Time	Steady
Turbulence Model	k-ω SST
Material	Water (Liquid)
Inlet Velocities	20 m/s & 30 m/s
Inlet Temperatures	60°C & 100°C
Outlet	Pressure Outlet
Discretization	Second Order Scheme
Residuals & Monitors	Area-weighted average temperature at outlet Area-weighted average velocity at outlet Mass flow rate balance
Initialization	Hybrid
Iterations	~2000 (Converged ~250)

4. Results

1. Velocity Contours

• For Velocity Contours:
  • Figure below shows how the flow velcoity changes at it transists from 2 inlets to outlet.
  • Red color shows max velocity points/regions & blue color shows the least, lengends can be seen on left center of all images

Velocity Streamlines, Vectors & Contours (Flow Doamin XY plane)

Temperature Contours

• For Temperature Contours:
  • Figure below shows that velocity contours and velocity vectors highlighting the flow direction and velocity changes.
  • Figure 4 shows Temperature at inlet 1 is 60^oC and at inlet 2 is 100^oC, as the flow progress the mixing of temperature can be observed.
  • Red color shows max temperature points/regions & blue color shows the least, lengends can be seen on left center of all images

Temperature Contours at outlet

Velocity and Temperature Profiles

• For Velocity & Temperature Profiles:
  • Line Coordinates at which the profile data points are extracted: (101.6, 203.2, 9.331), (203.2, 203.2, 1.5553). This line is at the outlet plane.
  • Temperature at 102.1 mm is 333.15 K and at 203.2 mm is 341.31 K. Maximum Temperature at 188.9 mm is 354.18 K
  • Maximum Velocity at 188.4 mm is 25.877 m/s

Temperature & Velocity Profile at Outlet

Discussion & Future Scope

There are two inlet same liquid i.e. water at different velocity (Inlet1 = 20m/s and Inlet2 = 30m/s) and temperature (Inlet1 = 60 degree Celsius and Inlet2 = 100 degree Celsius) are injected in the pipe and undergoes mixing and at Outlet generating:

• Mass Flow Average temperature = 336.507 K
• Max. Temperature at Mid-Section Line = 354.18 K

Mixing Elbow Problem was solved, and results were analyzed. Below is conclusion of findings:

• Maximum temperature recorded is 354.18 K and is not uniform over the entire Outlet of Pipe.
• From the Velocity and Temperature Contour it can be concluded that the flow is not mixed properly.

Temperature and Velocity recorded at outlet:

• Area Average of Temperature at outlet = 336.111 K
• Area Average of Velocity at outlet = 21.8739 m/s
• Mass Flow Average of Temperature on outlet = 336.507 K
• Mass Flow Average of Velocity on outlet = 22.1749 m/s

FLOW CONTROL STRATEGIES:

METHOD	MIXING EFFICIENCY INCREASES	PRESSURE DROP PENALTY
HELICAL STATIC MIXER	+50–70%	+15–20%
PULSATING FLOW	+30–50%	+5%
ACOUSTIC EXCITATION	+20–40%	Negligible

QUANTITATIVE COMPARISON METHODS:

METHOD	MECHANISM	PROS	CONS
CO-FLOW INJECTION	Secondary fluid injection	Simple implementation	Requires extra plumbing
ELECTROHYDRODYNAMICS	Electric field-induced vortices	No moving parts	High voltage needed
MAGETIC STIRRING	Ferrofluid + rotating magnets	Precise control	Limited to conductive fluids

Final Recommendation:
Reduce Smaller inlet Velocity (More CFD Simulations to identify the right velocity) and use Helical Static mixer

Recommended Repository Structure

CFD-Study-Globe-Valve/
│
├── README.md
├── Geometry image
├── Mesh images
├── Fluent_Case_Files
├── Results & Data

Author:
Ansh Vishal,
Aerospace Engineer
anshvishal215@gmail.com
LinkedIn