

مجله مكانيك سيالات كاربردي
Journal Of Applied Fluid Mechanics
ISSN 17353572
دوماهنامه داراي رتبه علمي  پژوهشي (علوم پايه) به زبان انگليسي
سال يازدهم، شماره 6




 Simulation of a Standard Store Separated from Generic Wing M. Sheharyar *, E. Uddin , Z. Ali, Q. Zaheer,A. Mubashar Pages 15791589 Abstract Full Text [PDF 1054KB]   Evaluation of store separation experimentally is expensive; time consuming and dangerous as human risks are involved. This results in development of computational methods to simulate the store separation. Store separation studies include store separation simulation and determination of linear and angular displacements of store under the influence of complex and nonuniform flow field of parent aircraft. In order to validate the methodology، the unsteady CFD results، obtained by coupling six degrees of freedom (6DOF) with flow solver، are compared with experimental results. Major trends are captured which are consistent with experimental results. Variation in store trajectory has been evaluated with different combinations of forward and rearward ejection forces. By increasing the magnitude of forward ejection force vertical displacement increases and store separates more safely from the wing. Moreover، effects of varying parent wing configuration on store trajectory has also been analyzed by incorporation of leadingedge flaps (LEFs). Store always separates in nose down condition due to LEFs which increases vertical displacement of store and thus safety related to store separation is enhanced.
Keywords: Store separation, Six degree of freedom, Trajectory simulation, Coupling of flow solver, Ejection forces, CFD analysis, Leading edge flap
  
 Smoothed Particle Hydrodynamics Method for ThreeDimensional Open Channel Flow Simulations D. Lَpez*, T. Ramos, P. Sلnchez, R. Marivela, R. Dيaz J. J. Rebollo F. R. Andrés, V. Cuellar, M. De Blas,J. L. Garcيa Pages 15991611 Abstract Full Text [PDF 930KB]   To date، the Smoothed Particle Hydrodynamics (SPH) method has been successfully applied to reproduce the hydrodynamics behind threedimensional flowstructure interactions. However، as soon as the effect of flow resistance becomes significant، the results obtained are not consistent with observations. This is the case for open channel flows (OCF)، in which the water surface is largely influenced by the boundary friction. The roughness generated by the current boundary condition methodologies is solely numerical and cannot be associated to physical values of friction. In light of this challenge، the authors present a novel formulation for the friction boundary condition. The new implementation includes an additional shear stress at the boundaries to reproduce roughness effects، allowing for the adequate threedimensional simulation of open channel flows using the SPH method. Finally، in order to reduce the high computational cost، typical of the Lagrangian models، without interfering in the representativeness of the SPH simulations، a criterion to define the adequate fluid particle size is proposed.
Keywords: Smoothed Particle Hydrodynamics (SPH), Open Channel Flow (OCF), Threedimensional Simulations, Bed roughness, Boundary friction methodology, Computational Fluid Dynamics (CFD)
  
 Energy Extraction Performance Improvement of a Flapping Foil by the Use of Combined Foil A. Boudis *, A. Benzaoui, H. Oualli, O. Guerri, A. C. Bayeul,Lainé, O. Coutier Delgosha Pages 16511663 Abstract Full Text [PDF 1570KB]   In this study، numerical investigations on the energy extraction performance of a flapping foil device are carried out by using a modified foil shape. The new foil shape is designed by combining the thick leading edge of NACA0012 foil and the thin trailing edge of NACA0006 foil. The numerical simulations are based on the solution of the unsteady and incompressible NavierStokes equations that govern the fluid flow around the flapping foil. These equations are resolved in a twodimensional domain with a dynamic mesh technique using the CFD software ANSYS Fluent 16. A User Define Function (UDF) controls the imposed sinusoidal heaving and pitching motions. First، for a validation study، numerical simulations are performed for a NACA0012 foil undergoing imposed heaving and pitching motions at a low Reynolds number. The obtained results are in good agreement with numerical and experimental data available in the literature. Thereafter، the computations are applied for the new foil shape. The influences of the connecting area location between the leading and trailing segments، the Strouhal number and the effective angle of attack on the energy extraction performance are investigated at low Reynolds number (Re = 10 000). Then، the new foil shape performance was compared to those of both NACA0006 and NACA0012 baseline foils. The results have shown that the proposed foil shape achieves higher performance compared to the baseline NACA foils. Moreover، the energy extraction efficiency was improved by 30.60% compared to NACA0006 and by 17.32% compared to NACA0012. The analysis of the flow field around the flapping foils indicates a change of the vortex structure and the pressure distribution near the trailing edge of the combined foil compared to the baseline foils.
Keywords: Flapping foil, Energy extraction, Power coefficient, Combined foil, CFD
  
تاريخ انتشار: 24/8/97 تلفن: 33915271 (031)
تاريخ درج در سايت: 22/8/97
شمار بازديدکنندگان اين شماره: 284




