Aerodynamics of V/STOL flight , Aerodynamics of V/STOL flight , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Aerodynamics of V/STOL flight

Efficient accelerators for PSO in an inverse design of multi-element airfoils

This paper presents a sensitivity and uncertainty analysis of the under-track loudness for a low-boom concept aircraft that has been modified to include small-scale surface deformations placed along the centerline of the aircraft’s underside. The small-scale surface deformations, or bumps, were defined using a one-dimensional Gaussian function and inverse distance weighting interpolation. The near-field solution of the low-boom concept aircraft was predicted by the in-house CFD solver UNS3D. Sonic boom propagation and loudness calculations were done by the NASA codes sBOOM and LCASB. The predicted near-field solution and loudness of the baseline aircraft geometry were found to be in excellent agreement with previously published CFD predictions of the same geometry. A surrogate model, based on radial basis functions, of the PLdB loudness metric was created with respect to the height and length of the bumps to perform the sensitivity and uncertainty analysis based on the discreet CFD data. It was found that the aircraft was relatively insensitive to bumps with a height less than 2 cm, and most sensitive to bumps with heights equal to or greater than 3 cm. The location and amplitude of the region of largest sensitivity was found to vary with respect to the length of the bump. Uncertainties in the bump lengths and height were introduced into the problem formulation and propagated using Monte Carlo sampling. The impact of the uncertainty in only bump height, only bump length, and in both bump length and height on the uncertainty of the loudness was examined. It was found that, by itself, the uncertainty in the height of the bump resulted in higher uncertainties in the loudness than when only considering the uncertainty in the length of the bump. Accounting for the uncertainties in both the length and height of the bump resulted in significantly higher variation of under-track loudness, but with the main source of loudness uncertainty still being related to the uncertainty in the height of the bump.

Controlling Sonic Boom Loudness Through Outer Mold Line Modification: A Sensitivity Study

Experimental investigation on tip-vortex flow characteristics of novel bionic multi-tip winglet configurations

This work describes the aerodynamic characteristics of an aircraft wing model with a Ruppell’s griffon vulture (RGV)-type winglet. A computational fluid dynamics (CFD) study using ANSYS 15.0 was conducted to study the effect of the RGV winglet on a rectangular wing. The NACA 65(3)-218 wing consists of 660 mm span and 121 mm chord length where the aspect ratio is 5.45. Eight different winglet configurations have been studied. Furthermore, the study is extended to study effect of cant angle and different angles of attack (AOA) to the winglet. A comparative study is done on aerodynamic features such as lift coefficient (CL), drag coefficient (CD), lift/drag ratio (CL/CD) and tip vortices to get the best RGV winglet design. The RGV winglet achieved highest CL compared to other types of winglets configuration. Based on contour plot analysis, the RGV winglet shows lower vortex formation compared to without winglet. The results show about 15 to 30% reduction in drag coefficient and 5 to 25% increase in lift coefficient by using an RGV winglet.

/pdf/investigation-of-aerodynamic-characteristics-of-a-wing-model-4kmfqbjrh0.pdf

Investigation of Aerodynamic Characteristics of a Wing Model With RGV Winglet

The wing tip device in this study was to mimic the wing tips of a soaring bird, featuring three smoothly blended elements. Each such multi-element winglet was integrated into a complete wing–tail–body aircraft configuration. The geometry of each of the three elements in the multi-element winglet was defined using 11 parameters, totaling 33 parameters for a complete multi-element winglet geometry. This design methodology used a three-dimensional geometry generation algorithm based on locally analytical smoothly connected surface patches, allowing for the creation of vastly diverse three-dimensional geometries with a minimal number of specified design parameters. A three-dimensional, compressible, turbulent flow, steady-state analysis was performed using a Reynolds-averaged Navier–Stokes solver on each configuration to obtain the objective function values. Each configuration was analyzed at a freestream Mach number of 0.25 and at an angle of attack of 11 deg to mimic the takeoff conditions of a passenger ai...

Multi-Element Winglets: Multi-Objective Optimization of Aerodynamic Shapes

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Multi-Element Winglets: Multi-Objective Optimization of Aerodynamic Shapes