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Geometry modelling

Key principles and recommendations

• Use the 3D tab as a tool to visually verify your input.
  • For highly complex geometries the 3D view in the zone form provides the accurate representation.
• Once the user is comfortable with the software, it's often a good idea to test the modeled geometry by generating a coarse mesh. This requires rapid navigation through the various stages of the software workflow.
• Equipment, lighting and occupants needs to be assigned to created geometries. Assigning geometries to CFD roles is described in section Thermal and airflow input. If not assigned, they will be modelled using default settings.
• Building bodies is one of the tools for creating geometry for the CFD domain.
• The zone will be the gross boundary for your CFD domain. Thickness of constructions (walls etc.) has no affect on the geometry of the CFD domain.

Import CAD

• Sketchup-files, SKP:
  • 3D tab -> Right-click -> Import CAD. 
  • Use properties to place object in x, y, z.
• OBJ files from Samples folder in IDA ICE:
  • Right-click a zone surface for placement -> Import CAD ->  C:\"ice folder"…\Samples\3d_objects\.
  • Use properties to place object in x,y,z.

Quick object placement in 3D tab: Press and hold the 'Ctrl' key, then left-click and drag your imported object to the desired position.

Extruded parts

• Double-click (open) a zone surface as base for the extruded part. In "Palette" drag and drop "Extruded geometry".
  • Use properties for x and y coordinates
  • Open the object for input of; distance from surface & depth (z)

Air terminals - define geometry and modify inlet and outlet areas

• Add terminals by opening a surface of a zone in 3D tab and drag and drop either a "Supply terminal" or a "Exhaust terminal" from the "Palette" on the left side.
  • Position it by draging it or using "Properties" to the left. 
• Supply terminal:
  Either keep a round basic supply terminal (enables control of inflow angles) or enable geometry (disables control of inflow angles but enables 3D shape of terminal)
  • Basic:
    • In General tab of the supply terminal set the terminal area (m²).
  • Geometric (extruded) representation:
    • Enable geometry in CFD tab for supply terminal
    • Enter values for surface offset, rotation and size
• Exhaust terminal:
  • Basic:
    • In General tab of the exhaust terminal set the terminal area (m²)
  • Geometric (extruded) representation:
    • Enable geometry in CFD tab for exhaust terminal
    • Enter values for surface offset, rotation and size
• Modifying area of air terminals:
  • If an extruded geometry is blocking a part of an inlet or a outlet of a terminal, that area of the air terminal will be ignored when the meshing operation starts. I.e. this is a way of modifying and fine-tuning the geometry that will be used in the CFD simulation. 
  • If all inlet and/or outlet areas are blocked the simulation will not produce reasonable nor correct result. In most cases this will cause an error message.

The Introduction Exercise

The goal of this exercise

The goal of the exercise is to model and simulate a simple case where cold downdraught from a tall window is prevented by a convector.

Animation tab must be enabled in IDA ICE

To visualize CFD results, the 64-bit Animation tab must be enabled.

• Options -> Preferences -> General -> Check "Use 64-bit diagram and animation (Beta)
• Restart IDA ICE -> Animation tab now visible when IDA ICE is restarted.

The Introduction Exercise - Geometry modelling

Building and zone

• Start a default building.
• Click on tab "Floor plan"
• Click on the zone and under "Properties" set height (size, z) to 4 m.

Window

• Click on tab "3D"
• Left-click the window object in the 3D view and under Properties set y min value to 0 (zero) and y size value to 3.5.

Occupant

• Right-click the floor of the zone in the 3D tab. Left-click and hold and move the mouse to navigate in the 3D view.
• Click "Import CAD"
• From the folder your ICE software is installed: ...\"Your folder"\Samples\3d_objects\
  • Choose "manequin-standing" and click "Open"
  • Left-click on the person object and under Properties set x=25.3, y=1, z=0.

Convector

• Double-click the floor of the zone in the 3D tab.
• Click "Palette" to the left.
  • Drag and drop an "Extruded geometry" to the floor area.

• Left-click the Extruded geometry, and click "Properties" to the left.
  • Set x size to 1.1, y size to 0.15, x min to 0.73 and y min to 0.15 (m).
• Double-click the Extruded geometry and set "Distance from surface" to 0.1 m and "Depth" to 0.2 m. "Depth" in this case will be the height of the convector.
• Look at the resulting geometry in the 3D tab.

Air terminals

• In 3D tab, double-click the East inside wall. Under "Palette" to the left drag and drop an Exhaust terminal to the upper center of the wall (according to image below). Close the window.
• Double-click the smallest inside wall (North wall) and drag and drop a Supply terminal to the upper center of the wall (according to image below).

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