OpenFOAM CFD — Laminar Flow Maldistribution Mitigation

Chevron vs Teardrop Sheet Insert Geometries

A comparative CFD study using OpenFOAM 12 (foamRun / incompressibleFluid) to evaluate two sheet insert geometries — chevron and teardrop — for mitigating flow maldistribution in a laminar channel flow.

---

Problem Statement

Flow maldistribution (non-uniform velocity across a cross-section) reduces the effectiveness of heat exchangers, reactors, and filtration systems. This study evaluates surface-mounted protrusions on a thin sheet as passive flow distributors.

---

Cases

Case	Insert Geometry	Description
laminar_sheet_chevron	Triangular chevron	Sharp apex pointing upstream, 120 mm wide × 200 mm long × 10 mm tall
laminar_sheet_teardrop	Biconvex teardrop	Streamlined lens shape (intersection of 2 circles r=145 mm), 10 mm tall

Both cases share identical flow conditions:

• Channel: 200 mm × 1000 mm, height 97 mm
• Fluid: Air, ν = 1.563 × 10⁻⁵ m²/s
• Inlet: Uniform U = 0.5 m/s
• Re ≈ 3.2 (deeply laminar)
• Mesh: ~142,000 cells (snappyHexMesh, surface refinement level 2)
• End time: 10 s

---

Key Results

Metric	Chevron	Teardrop	Winner
Velocity Uniformity Index (γ)	0.7263	0.7269	Teardrop
Coefficient of Variation (CoV)	0.4510	0.4496	Teardrop
Stagnation fraction	7.55%	5.39%	Teardrop −29%
Max lateral spread (Ux)	0.099 m/s	0.157 m/s	Teardrop +58%
Max vertical mixing (Uz)	0.092 m/s	0.137 m/s	Teardrop +50%
Pressure drop	0.122 Pa	0.113 Pa	Teardrop −7.4%

→ Teardrop wins 6–1. The streamlined biconvex shape avoids the blunt-body separation wake that the sharp chevron creates, resulting in better lateral redistribution, less stagnation, and lower pressure penalty.

---

Comparative Plot

---

Full Postprocessing Report

See cfd_maldistribution_report.md for detailed analysis including velocity distributions, pressure field stats, physical interpretation, and design recommendations.

---

Geometry Files

The insert geometries are defined in OpenSCAD:

• laminar_sheet_chevron/sheet_chevron.scad
• laminar_sheet_teardrop/teardrop.scad

---

Repository Structure

├── laminar_sheet_chevron/       # Chevron insert case
│   ├── 0/                       # Initial conditions (U, p, T)
│   ├── constant/                # Physical properties, mesh
│   ├── system/                  # controlDict, fvSchemes, fvSolution, snappyHexMeshDict
│   └── sheet_chevron.scad       # Insert geometry (OpenSCAD)
├── laminar_sheet_teardrop/      # Teardrop insert case
│   ├── 0/                       # Initial conditions (U, p, T)
│   ├── constant/                # Physical properties, mesh
│   ├── system/                  # controlDict, fvSchemes, fvSolution, snappyHexMeshDict
│   └── teardrop.scad            # Insert geometry (OpenSCAD)
├── cfd_maldistribution_report.md   # Detailed postprocessing report
├── cfd_maldistribution_analysis.png # Comparative plots
└── README.md

Note: Time-step field data (U, p, phi) and zip archives are excluded via .gitignore due to file size.

---

Software

• OpenFOAM 12
• OpenSCAD (geometry generation)

Author

goatnath — 2026