The perfect beer pour is a matter of some debate; in the United States and in Southern England, we typically prefer a small amount of head with the maximal amount of beer whereas in other areas of Europe, a beer should be served with a large froth head, and in other areas still, the amount of head is dictated by the type and style of beer. One thing that is agreed upon, however, is that the angle over which the beer is poured is an essential component in ensuring that the beer's froth (and thus taste) is optimal.

Image Source: The Perfect Pour: Beer Foam Physics and the Art of Dispensing Beer

    Generally the beer should be poured (regardless of whether from tap, can, or bottle) with the glass held at approximately 45˚ initially and gradually shifting to perpendicular to a table or flat surface on which to rest. The reason fore the initial angled tilt of the glass is to promote a greater surface area of liquid to wash over the glass, which in turn allows a greater amount of CO2 to fall out of solution of the brew. This action also reduces the final velocity with which the fluid will impact the bottom of the glass, thereby minimizing the buildup of froth which will prevent the beer from becoming "too heady too quickly." From there, the angle is adjusted to a straight pour to promote the formation of beer head to taste.

     One may consider the angle of a beer pour essential in controlling the vorticity of the fluid; in fluid dynamics, vorticity is a vector quantity which tells us the tendency of a fluid particle to rotate about a particular point. Vorticity is given by the equation:

$ω = ∇ × V$ 

where $ω$ is the curl of the of the fluid, V is the flow velocity, and $∇$ is the del operator. In minimizing the overall fluid vorticity, one minimizes the agitation of the fluid particles, and thus directly minimizes the amount of CO2 falling out of brew solution. As such, the angle plays the greatest role in controlling the vector agitation of beer particles.