Dynamic stall under large Reynolds numbers and large reduced frequencies has a significant effect on the performance of the wind turbine blades,helicopter rotors,etc.So the dynamic stall physics of the NACA0012 airfoi...Dynamic stall under large Reynolds numbers and large reduced frequencies has a significant effect on the performance of the wind turbine blades,helicopter rotors,etc.So the dynamic stall physics of the NACA0012 airfoil under a large Reynolds number of Re=1.5×106 was studied using experimental and numerical methods.The reduced frequency range was k=0.035-0.1.The unsteady flow field in dynamic stall was studied in detail by using the transient pressure measurement and the numerical simulation based on the unsteady Reynolds-averaged Navier-Stokes(URANS)equation.And the time-frequency characteristics of the dynamic stall were studied using the wavelet analysis.The study showed that the aerodynamic performance during the dynamic stall was dominated by the shear layer vortex(SLV)and the leading edge vortex(LEV),and the phase difference between the SLV and the LEV was the key factor in the exist-ence of the bimodal characteristics of the aerodynamic force/moment.There was a significant linear correlation between the negative peak of the vortex-induced Cp and the Cn in the reduced frequency range studied in this paper.During the convection of the near-wall LEV to the trailing edge,the high-frequency features firstly decay,and the multi-scale structures of the LEV become more significant as the reduced frequency gradually increases.展开更多
The objective of this paper is to derive the analytical solution of the EOQ model of multiple items with both demand-dependent unit cost and leading time using geometric programming approach. The varying purchase and ...The objective of this paper is to derive the analytical solution of the EOQ model of multiple items with both demand-dependent unit cost and leading time using geometric programming approach. The varying purchase and leading time crashing costs are considered to be continuous functions of demand rate and leading time, respectively. The researchers deduce the optimal order quantity, the demand rate and the leading time as decision variables then the optimal total cost is obtained.展开更多
基金the Key Laboratory of Flow Visualization and Measurement Techniques,AVIC Aerodynamics Research Institute(XFX20220502)the foundation of National Key Laboratory of Science and Technology on Aerodynamic Design and Research(No.61422010401).
文摘Dynamic stall under large Reynolds numbers and large reduced frequencies has a significant effect on the performance of the wind turbine blades,helicopter rotors,etc.So the dynamic stall physics of the NACA0012 airfoil under a large Reynolds number of Re=1.5×106 was studied using experimental and numerical methods.The reduced frequency range was k=0.035-0.1.The unsteady flow field in dynamic stall was studied in detail by using the transient pressure measurement and the numerical simulation based on the unsteady Reynolds-averaged Navier-Stokes(URANS)equation.And the time-frequency characteristics of the dynamic stall were studied using the wavelet analysis.The study showed that the aerodynamic performance during the dynamic stall was dominated by the shear layer vortex(SLV)and the leading edge vortex(LEV),and the phase difference between the SLV and the LEV was the key factor in the exist-ence of the bimodal characteristics of the aerodynamic force/moment.There was a significant linear correlation between the negative peak of the vortex-induced Cp and the Cn in the reduced frequency range studied in this paper.During the convection of the near-wall LEV to the trailing edge,the high-frequency features firstly decay,and the multi-scale structures of the LEV become more significant as the reduced frequency gradually increases.
文摘The objective of this paper is to derive the analytical solution of the EOQ model of multiple items with both demand-dependent unit cost and leading time using geometric programming approach. The varying purchase and leading time crashing costs are considered to be continuous functions of demand rate and leading time, respectively. The researchers deduce the optimal order quantity, the demand rate and the leading time as decision variables then the optimal total cost is obtained.
