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Initial conditions are the starting values in the domain. The closer the initial conditions are to the result values, the less time the simulation will take to solve. You should have an idea of what values you’re expecting but if you don’t know or don’t care to estimate them, you can leave the default values as they are. Expand the Initial conditions section by clicking the plus sign in a box on the left. Gauge pressure can probably be left as zero. For velocity most of our simulations were run at 20 m/s (but if you are interested in a different speed simply use your speed instead). This means that most of the domain will have air moving close to a speed of 20 m/s, with some regions with faster moving air and other regions with slower moving air. So I use an initial velocity of -20 m/s in the z direction. For κ and ω, there are ways to estimate these values that can be found online. The values first estimate that I found were gave values of 0.303 m2/s2 and 2.871 s-1, however I have also seen an estimate that gives values closer to 4e-4 m2/s2 and 20 s-1. Both sets of values work, although the 2nd set of values are supposedly more appropriate for external aerodynamics, according to the source that published them.
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It might be worth reviewing what’s happening in the domain. When driving a car with no wind, the air is mostly stationary and the car is moving at a velocity u. (Not all the air is stationary though, as some air is displaced by the car’s motion.) However, you may have noticed that I talk about the air moving, rather than the car moving. When simulating something like this, it’s common to use the car as your frame of reference. This means that the car will have a velocity of 0, while the air (and the road) will be travelling with a velocity of -u. |
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After the simulation finishes, you’ll want to process the results to make them easier to understand and interpret.