Bernoulli's Principle applies (apart from friction and viscosity etc.) to both the air and the fuel, so that the pressure reduction in the air flow tends to be proportional to the square of the intake airspeed, and the fuel in the main jets will obtain a speed as the square root of the pressure reduction so the two will be proportional to each other. If the pressure reduction is taken as from a change of area along the air flow rather than from ambient pressure to the fuel entry point the effect can be described as the Venturi effect, but that is simply a derivation from the Bernoulli principle at two positions. The actual fuel and air flows are more complicated and need correction. This might be done variously at lower speeds or higher speeds, or over the whole range by a variable emulsion device to add air to the fuel after the main jets/s. In SU and other (e.g. Zenith-Stromberg) variable jet carburetors, it was mainly controlled by varying the jet size.
Bernoulli's Principle applies (apart from f.riction and viscosity etc.) to both the air and the fuel, so that the pressure reduction in the air flow tends to be proportional to the square of the intake airspeed, and the fuel in the main jets will obtain a speed as the square root of the pressure reduction so the two will be proportional to each other. If the pressure reduction is taken as from a change of area along the air flow rather than from ambient pressure to the fuel entry point the effect can be described as the Venturi effect, but that is simply a derivation from the Bernoulli principle at two positions. The actual fuel an,d air flows are more complicated and need correction. This might be done variously at lower speeds or higher speeds, or over the whol?e range by a variable emulsion device to add air to the fuel after the main jets/s. In SU and oth.er (e.g. Zenith-Stromberg) variable jet carburetors, it was mainly controlled by varying the jet size.