Fluid Flow and Heat Transfer in ANSYS Fluent | Conjugate Heat Transfer

Main Ideas / Concepts Conveyed

• The video demonstrates how to model conjugate heat transfer (CHT) in ANSYS Fluent:
  • Heat is generated volumetrically inside a heated solid cylinder.
  • Air flows through/around the cylinder and carries heat away via convection.
  • The outer surfaces of the solid interact thermally with the surrounding fluid through interfacial heat transfer.
• It presents an end-to-end ANSYS workflow:
  • Geometry creation (ANSYS SpaceClaim) → Meshing → Fluent setup/solve → CFD-Post visualization

Methodology (Step-by-Step Workflow)

1) Geometry Setup (SpaceClaim)

Create the heated solid cylinder

• Create a circle on the GX plane using chosen dimensions.
• Pull/extrude the cylinder in both directions.
• Example dimension mentioned: 30 mm.

Create the outer air domain

• Add an outer rectangle-based region to represent the surrounding flow space.
• Create a new plane slightly away from the outer cylinder surface to separate solid and fluid regions.
• Use Define rectangle from Center to maintain symmetry.
• Pull/extrude the outer flow geometry mainly in the bottom direction (not both).

Handle overlapping solid/fluid geometry

• Use a sectional plane to inspect the interior and confirm overlaps.
• Resolve overlaps using Combine / Boolean operations:
  • Order matters:
    1. Select outer geometry
    2. Use cutter
    3. Select inner geometry
• This produces multiple parts; delete duplicates (e.g., the duplicated inner part) if needed.
• Final parts:
  • Heated solid cylinder
  • Outer air flow domain

Name boundary surfaces

• Create Named Selections under Groups:
  • Inlet (named selection)
  • Outlet (named selection)
  • Wall for outer surfaces (default no-slip wall condition)

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2) Meshing Workflow (ANSYS Meshing)

Import geometry

• Import using Import Geometry as a single file (default options).

Local sizing near the solid–fluid interface

• Enable local sizing to properly capture interfacial heat transfer.
• Choose size control type: face size.
• Apply it to the heated cylinder surface (inner solid).
• Set target/element size to about 500 microns.
• Then:
  • Generate surface mesh
  • Optionally set minimum sizing (keep maximum default)
  • Adjust growth rate if required

Define shared topology / interfaces

• Use the option appropriate for a solid + fluid geometry (the “third option” as described).
• Set s-topology method: joint intersect.
  • joint intersect: overlaps of similar-shape/size surfaces
  • interface connect: when interfaces are defined on both sides (fluid and solid)

Update boundaries and create regions

• Click Update boundaries.
• Create air fluid region outside.
• Define two regions total:
  • Inner solid (heated cylinder)
  • Outer air flow region

Add boundary layers

• Choose a growth option like grow on solid–fluid interface.
• Increase layer count to improve capture of heat transfer/flow physics.
• Example: 10 layers.

Generate volume mesh

• Click Generate volume mesh.
• Expect refinement near interfaces due to:
  • local sizing + boundary layers
• Mesh size mentioned: ~1+ million cells (approximately).

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3) Fluent Setup (Solution)

Study type

• Use Steady State.

Enable physics

• Enable the Energy equation (required for conjugate heat transfer).

Turbulence model

• Keep laminar (for simplicity).

Materials

• Use default materials:
  • Air for the fluid
  • Aluminum for the solid (heated cylinder)

Cell zone setup

• Assign zones properly:
  • Air zone → fluid region
  • Aluminum zone → solid region

Operating condition

• Use the default operating condition.

Boundary conditions

• Inlet:
  • Velocity inlet
  • Specify velocity magnitude
  • Default temperature option mentioned
• Outlet:
  • Pressure outlet
• Walls:
  • No-slip (default)
  • Thermal condition: zero flux at walls (as stated; can be changed)

Interfacial conditions

• No special manual interface setup required.
• The shared topology / Fluent handles interface heat transfer.

Heat generation in the solid (key CHT feature)

• For the heated cylinder (solid zone), add an energy source:
  • SOURCES / energy source term
  • Number of energy sources: 1
  • Heat generation type: constant volumetric heat generation
  • Example value mentioned: 2 million (units implied by Fluent’s volumetric heat generation setting)

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4) Initialization, Iteration, and Visualization During Solve

Initialization

• Use hybrid initialization.

Solution controls

• Mentioned numerical approach: PISO time-step method (even though the case is steady-state).
• Define:
  • number of iterations
  • reporting intervals
  • profile update intervals

Optional contour monitoring during calculation

• Set up contours to visualize during iterations:
  • Create a plane (example: Y=0 plane described as “Y plane … as XAL to Z” / “plane 5”)
  • Plot Temperature
  • The solid may be invisible at first, then appears as the solution progresses

Run the solve

• Click Calculate and iterate until convergence.

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5) CFD-Post Post-Processing

Refresh/open CFD-Post

• After Fluent completes, refresh/open CFD-Post.

Visualization workflow

• Create planes (examples):
  • Symmetry 1 plane on XY/GX with Y=0 (as described)
  • Symmetry 2 perpendicular plane
• Create contours
  • Variable: Temperature
  • Use local range / location selection on each plane
• Create volume rendering
  • Render temperature/energy-related distribution across all domains
  • Visualize energy transfer between fluid and solid

Main Lessons Summarized

Conjugate heat transfer in ANSYS Fluent requires:

• Proper solid + fluid geometry separation
• A mesh refined near the solid–fluid interface (local sizing + boundary layers)
• Enabling the Energy equation
• Defining volumetric heat generation inside the solid
• Correct inlet/outlet and solid/fluid thermal boundary settings
• Using CFD-Post to visualize temperature fields and energy transfer

Speakers / Sources Featured

• Unnamed tutorial instructor (speaking throughout the video)
• Software/toolchain referenced as sources:
  • ANSYS SpaceClaim
  • ANSYS Meshing
  • ANSYS Fluent
  • ANSYS CFD-Post
• Links referenced:
  • A previous DesignModeler-based CHT video (mentioned as being in the description)
  • A separate resource/video explaining the s-topology “joint intersect” method (referenced in the description)