Effect of Localised Pressure Depression and Rain on Aerodynamic Characteristics of MALE UAV

This paper presents the effect of the local low-pressure region in the atmosphere and rain on aerodynamiccharacteristics of medium altitude long endurance unmanned aerial vehicle (MALE-UAV) configuration duringcruise/loiter. Computations are performed using CFD++, a commercial CFD software suite. A large low-pressuredepression past the MALE UAV (symmetrically and asymmetrically) with pressure 10 – 15 % lower than the freestream pressure and a widespread rainfall type with a rainfall rate of 1195 mm/hr., are considered for CFD simulation.A large low pressure that spans the whole MALE-UAV results in a decrement in both lift and drag, but does not affect the yawing and rolling moments significantly. However, a low-pressure region that engulfs only one-half of MALE UAV causes sudden/abrupt changes in rolling and yawing moments. The effect of rain causes a significant decrease in a lift at higher alpha, accompanied by a decrease in stall angle of 2 degrees, and a significant increase in drag. From the study, a Standard Operating Procedure (SOP) was adopted to fly UAVs in adverse weather effects,such that the aircraft can be operated with a velocity higher than 1.3Vstall and at a power setting not less than 75% of max power capacity

Empirical and Numerical Analysis of Aerodynamic Drag on a Typical SUV Car Model at Different Locations of Vortex Generator

The aerodynamic characteristics are concerned with the fuel consumption rate and the stability of a high speed vehicle. The current research aims at studying the aerodynamic behavior of a typical SUV vehicle model mounted with the vortex generator (VG) at various linear positions with reference to its rear roof edge. The flow field around the vehicle model was observed at different wind speed conditions. It had been determined that at the instance of lower wind speed, the VG had minimal effects of aerodynamic drag on the vehicle body. However, at the instance of higher wind speed conditions the magnitude of the drag force decreased significantly. Vehicles move at higher speeds in the highways, location of the VG varied towards the upstream of the vehicle due to early flow separation. Therefore test were conducted at different wind speeds and locations of VG. The numerical simulation conduced in this study provides flow characteristics around the vehicle model for different wind speeds. The realizable k−ε model was used to simulate and validate the empirical results in an effective manner. By using experimental data, the drag was reduced by 9.04 % at the optimized VG location. The results revealed that the induced aerodynamic drag would determine the best car shape. This paper provides a better understanding of VG positioning for enhanced flow separation control

COMPUTATIONAL ANALYSIS OF F LOW BEHAVIOR OVER THE MULTISTAGE LAUNCH VEHICLE WITH STRAPONS

ABSTRACT Technology has the enemy of nature in one way. But sometimes technologies do come out as an exception to the above rule. In this paper conclude that multi-stage launch vehicle with strapons is a complex configuration to know the flow behaviour over it. Generally extensive wind tunnel testing is done to understand the flow characteristics of such a configuration with the Computation Fluid Dynamics (CFD) as a design tool, it is appropriate to make use of its technology to understand the complex flow behaviour over a multi-stage launch vehicle with strapons. In the present paper conclude the flow behaviour over a typical multi stage launch vehicle with strapons was known using commercial CFD software. This involves choice of flow model, discretization, grid generation, solution technique and analysis of results. Grid generation and body shape generation are done in Structured and an unstructured grid on 2D, and it is generated to know the effect of flow behaviour. Both Euler and Navier-Stokes solvers are attempted. Sensitivity of results on turbulence models is analyzed

Reduction of Aerodynamic Drag Force for Reducing Fuel Consumption in Road Vehicle using Basebleed

This paper presents the study of the overall aerodynamic performance of road vehicles and suggests a method to reduce the drag force and also to find the optimum location for placing basebleed in a car using aerodynamic principle. The overall aerodynamic drag force is reduced by eliminating wake region at the rear side of the car and reducing pressure in the front region of the car by delaying the flow separation. This improves the overall aerodynamic performance of the car thereby reducing fuel consumption, as well as improving stability and comfort by the attachment of basebleed. The wind tunnel tests are conducted for a subscale model of car with the basebleed at various locations along the front and rear side of the car in both X and Y directions. The coefficient of drag (CD), the coefficient of lift (CL) and coefficient of side force (CS) for the car is measured to interpret the effect of flow conditions on the car model. The experimental result reveals that the attachment of base bleed at an optimum position in the front and rear side of the car improves its performance and decreases drag coefficient by 6.188 %

Pressure distribution of rotating small wind turbine blades with winglet using wind tunnel

425-429This study presents pressure distribution over an envelope of blade with and without winglets for a small wind turbine in boundary layer wind tunnel. Different winglet configurations were tried based on winglet height and curvature radius. Pressure measurements were made with different chordwise and spanwise locations on the blade with and without winglets nearby tip region. Winglet improves overall pressure difference between pressure surface and suction surface. Presence of winglet seemed to have the pressure increased at 0.3c and maximum pressure difference was observed at a span of 0.95R for all winglet configurations. In suction, surface pressure decrease was 10% for all winglet configurations