Natural Convection

Discussion created by 1-1NHKU5 on Jun 15, 2008
Just getting started with FW. Went through the tutorial and it all made sense.

...now I have a problem.

I am simulating an aluminum heatsink under natural convection. The assembly consists of an empty enclosure with a hole on the bottom and another on the top, directly above it.

Inside is the heatsink. The channels between the fins are aligned vertically, in other words, if air flow from bottom to top it will flow between the fins. The holes are larger than the heatsink. The heatsource is applied to the surface opposite where the fins are.

I've setup lids on both openings. Both lids are configured as pressure openings at Environment Pressure.

I've enabled Gravity for the simulation.

The goal is max heatsink temperature.

OK, that's the setup. Here's the problem:

When I display the flow trajectory along the Y axis (vertical) FlowWorks says that air is flowing downward rather than the opposite. The heatsink has over 200W going into it...it'd be impossible for natural convection to flow downward.

Obviously there's something wrong with my configuration. Any secrets to setting-up a simple natural convection simulation?