INVESTIGATION OF PREDICTIVE METHODS FOR FLOW RESISTANCE IN CHANNEL WITH ASYMMETRIC RIB ARRANGEMENTS UNDER ROTATING CONDITION

Turbine blade cooling demands vary between the leading and trailing surfaces. To achieve a refined design of blade cooling structures and maximize the utilization of cooling air, an asymmetric ribbed structure design method is proposed. The prediction of resistance is a crucial issue that urgently needs to be addressed in the design of this structures. Numerical simulation (Large Eddy Simulation) is adopted to investigate the flow characteristics and resistance properties of straight channels with asymmetric (different rib spacing) and symmetric rib arrangements, within the range of Re=30000 and Ro=0-0.5. The ribbed channel’s friction factor is analyzed under rotating condition. The asymmetric effects within the rotating ribbed channel and the mechanism of rotational impact on the flow are revealed, and a predictive method for the flow resistance in rotating asymmetric ribbed channels is summarized and proposed. Placing asymmetric ribs on the wall causes the airflow to shift and squeeze toward positions of lower resistance, creating a "rib-induced pushing effect" and leading to a trend of resistance between wall surfaces moving towards equilibrium development. Affected by this effect, the peak streamwise velocity shifts towards the side without ribs by 11% in single-sided ribbed channel under stationary conditions. In double-sided ribbed channels, the peak streamwise velocity increases by 13% compared to a smooth channel. Under rotational conditions, the Coriolis force effect acts in conjunction with the rib-induced propulsion effect on the airflow, resulting in regular flow within the channel. Therefore, the Coriolis force effect and ribbed-induced pushing effect are the main factors affecting the flow resistance in the rotating asymmetric rib channel, and the flow resistance coefficient in the rotating asymmetric ribbed channel can be judged according to their magnitude. In this paper, a method for predicting the flow resistance of asymmetric ribs is proposed, considering the coupled effects between wall surfaces.