Often the models and equations rely on making assumptions in order to simplify the problem (cue the joke about physicist and the spherical cow). This is one of the reasons thing are designed with tolerances and safety factors.
Software like CAD and particularly Computational Fluid Dynamics (CFD) packages can simulate the problem but at least with CFD you would typically perform other types of verification such as wind tunnel tests etc.
or Heat Exchanger efficiency calculations (https://en.wikipedia.org/wiki/Logarithmic_mean_temperature_d...) etc.
Often the models and equations rely on making assumptions in order to simplify the problem (cue the joke about physicist and the spherical cow). This is one of the reasons thing are designed with tolerances and safety factors.
Software like CAD and particularly Computational Fluid Dynamics (CFD) packages can simulate the problem but at least with CFD you would typically perform other types of verification such as wind tunnel tests etc.