The drag coefficient is a function of several parameters like shape of the body, Reynolds Number for the flow, Froude number, Mach Number and Roughness of the Surface. The characteristic frontal area - A - depends on the body.

(1) can be written: C (~/) -- ½P CDo ( 1 ~- k ~/) where ~P is measured in radians (2) Here A is the train frontal area, CDO is the total aerodynamic drag coefficient at zero yaw, k is the yaw correction factor and p is air density. This site lists some values for the coefficient of friction for ice. According to Eq (5), the aerodynamic drag coefficient of the train model can be calculated as C x = 0.3504. For l=400 m, corresponding to the length of 16 trains, about 90% of the previous termaerodynamicnext term drag is attributed to the friction drag on the middle part of the train… The coefficient of rolling friction for a wheel-rail interface is approximately 0.001, while the coefficient of static friction for a steel-on-steel interface is approximately 0.5. How Efficient is a Freight Train?

The drag coefficient is a unit-less value that denotes how much an object resists … Therefore, it requires far less force to move a rail car with freely moving wheels than one with the wheels locked. The total aerodynamic drag term in eqn.

Objects drag coefficients are mostly results of experiments.

For ice skates on ice, it seems the value could be as low as 0.005.