flow around a cylinder

Lift, or downforce as its known in the motor racing world, is the force generated perpendicular to the direction of travel for an object moving through a fluid (gas or liquid). The same effect occurs when a fluid moves over a stationary object, such as an airfoil in a wind tunnel. Airfoils are the most efficient shapes found so far that can generate lift while at the same time minimizing drag. Drag is an unavoidable consequence of an object moving through a fluid. Drag is the force generated parallel and in opposition to the direction of travel for an object moving through a fluid. Drag can be broken down into the following two components: L = CL . A . qinf & D = CD . A . qinf

where: L is the lift force, CL is the dimensionless lift coefficient, D is the drag force, CD is the dimensionless drag, coefficient, A is a reference area

qinf = 1/2 rhoinf . Vinf2

where: rhoinf is the free stream fluid density Vinf is the free stream fluid speed he force on a single mesh element is defined as: Fi = (pi . ni + taui) . Ai

where: pi is the pressure at the center of the element taui is the wall shear stress at the center of the element Ai is the element area ni is the element normal direction i is the ith element