Animprovedlow-Reynolds-number k‐~modelisadoptedto predictturbulente owswitha nonstationary boundary.Theperformanceoftheadoptedmodelise rstcontrastedwithdirectnumericalsimulationdataoftheturbulent plane Couette ‐Poiseuille e ow. Detailed e ow structure is captured accurately by the model, in particularthe reduction of theshearstress and, hence, the turbulent kinetic energy due to thepresence of the moving wall. The validity of the present model in computing complex e ows within rotating disk cavities is further examined. Flows with two different rotational Reynolds numbers are investigated, and the predicted mean and turbulence results are also contrasted with measurements. The ine uence of rotation on the e owe eld and turbulence modeling is investigated by sensitizing the turbulence model coefe cient to rotational Richardson number, and the effect is found to be marginal. Because the internal e ow structure of the rotating disk cavities is induced by the diffusive transport of thetangential momentum from therotorinto theinterior, thepredicted thickness of the Ekman layer isfound to be critical to the correct predictions. The adopted model reproduces correctly the gradual thickening of the Ekman layers from small to large radii, which is due to the transition from laminar to turbulent regimes, especially on the rotor side within the disk cavities. The elevated level of turbulence on the stator side compared to that on the rotor side is also predicted correctly by the present model.