One thing that has always puzzled me is the fact that in a venturi, air accelerates as it approaches the narrow part of the structure. there are those that argue with the fact that pressure has to raise first , because as we all know, acceleration has to be caused by an increased force ( raised pressure) However, being true to what ive learned over the years, im sticking to the law and equations of bernoulli and trying to figure out how air accelerates, as pressure goes down as the entrance to the narrow part of the venturi has less and less volume. we all know bernoulli's equation of pressure energy, (air pressure) kinetic energy(speed and mass) and potential energy (density, height), all being equal for the flow on both sides of the venturi. one thing i have heard is that the air molecules are vibrating (moving around) at near 1000mph speeds, so when the air molecules hit the sides of the entrance of the venturi, the molecules pointed in the right direction speed up the flow, and the others are bouncing off the sides back into the flow.. so, the air molecules get spaced apart, the pressure drops and the speed increases... the opposite happens on the reverse side (the diffuser side) where the air flow hits the greater volume, the speed decreases, and the pressure increases.. so, its kind of like a chicken and egg situation. does the lower molecules getting spaced out due to the converged flow, speed them up, so is less mass, with the same force that they started with at the entrance? in other words to keep consistent with newtons 2nd law, the force says the same, but the mass went down, so the speed could go up. or is it a newton 3rd law where the pressure does go up as the air is compressed at the mouth of the venturi, causing an equal and opposite reaction of the air to accelerate based on the increased force at the mouth of the venturi (this doesnt seem right as we know, the pressure always goes down and flow speeds up. over an airplane wing, there is a similar paradox. the air does get compressed at the leading edge, and is that higher edge what feeds the higher speed, lower pressure air flow over the top of the wing? i dont think so, as you would think the under flow speed would accelerate, yet it doesnt. so, what causes the faster flow over the wing... the fact that the laminar flow, is taking a longer path, so it needs to accelerate to keep the same mass flow rate over it? this causes the molecules to space out and speed up? so, the force stays the same, the mass value or density goes down, and the velocity goes up. (where it goes back to the original speed as it comes off the wing at the rear.) the confusion for most is that its the fast moving air that creates the lower pressure , when in fact , its really the change of the speed of the air that reduces or increases the pressure of the flow field..