(Aditya asked)

Answer:

There is a relation between pressure and velocity of flow in fluids.

Bernoulli’s principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid’s potential energy.

Bernoulli’s principle can be derived from the principle of conservation of energy. This states that, in a steady flow, the sum of all forms of mechanical energy in a fluid along a streamline is the same at all points on that streamline. This requires that the sum of kinetic energy and potential energy remain constant. Thus an increase in the speed of the fluid occurs proportionately with an increase in both its dynamic pressure and kinetic energy, and a decrease in its static pressure and potential energy. (Courtesy: Wikipedia http://en.wikipedia.org/wiki/Bernoulli%27s_principle)

But there is some misconception in the question you asked.

Smoke rising in a straight path from a cigarette is undergoing laminar flow. After rising a small distance, the smoke usually changes to turbulent flow, as it eddies and swirls from its regular path.

 Ref: http://www.grc.nasa.gov/WWW/K-12/airplane/bern.html