We research the aerodynamics of the vehicle. Usually, there exists turbulence, which will cause the time-varying measurement of the force. The unsteady flow field determines we could not get a definite result. Often, we get a rough result. However, this time I calculate the force with CFD (computational fluid dynamics).
However, due to the numerical error, there are some apparent flaws in the results. For example:
- The force coefficient is $0.00076$. However, in the physical world, we usually have two digits after the decimal point. Should I change $0.00076$ to $0$?
- One of the net forces should be $0$ because two forces $F_1$ and $F_2$ of the same size but opposite direction will cancel each out. However, because of numerical error again, $F_1 = 0.28$ and $F_2 = -0.27$ (after I keep only two digits after decimal point), which results in a net force of $0.01$. Should I leave it as $0.01$, or change it into $0$?
The numerical method produces too precise result, and they are too good to be true. In practice, it is impossible to get such a precise result. I have compared one of the results with the experimental results and found that there is 10% error between them.