A numerical study is made of a flow in a cylinder with a rotating wavy endwall disk. The aim is to describe differences in the flow fields when there is sinusoidal wavy obstacle characterized by amplitude(a) and wave number(N). The Ekman number(Ek) is set to $10^{-4}$ and the aspect ratio(R/H) fixed to 1. For 40 combinations of amplitude(a) and wave number(N),numerical results are acquired. As endwall disk roughness(aN) increases, the azimuthal velocity component(v) increases drastically. Also, the Primary volume flow rate($Q_p$) does.
The reason of activating θ directional flow is based on increasing of torque(T) transported by endwall disk as roughness(aN) increases. The torque coefficients($C_T$) vary linearly as endwall disk roughness has lager value. The torque coefficients($C_T$) are determined by normal azimuthal velocity gradients(dv/dn) and surface area elements(ds). As roughness increases, surface area elements(ds) help to increase torque(T), but velocity gradients(dv/dn) do not. Synthetically, torque increases by surface area increasing effect and it causes activation of swirling motions in a cylinder.
