Papers by Keyword: Drag

Abstract: Aerodynamics contributed directly on the energy efficiency and fuel consumption reduction of heavy vehicles in addition to its stability. The present study examines numerically the aerodynamics of heavy vehicles considering different drag-reduction devices using SolidWorks programme. Four different drag-reduction devices such as Base flaps, filled boat tail, Deflector and Rear offset plate in order to compare them with the baseline model. the results showed that the reflector contribute in more drag formation while Rear offset plate leads to lower drag.

Abstract: The development of drag and lift balance aimed to modify and creating a measuring instrument that may be used in the field of aerodynamics or in testing aerodynamic properties. This measurement is in the form of wind speed on an object model such as airfoils, building models and automotive technology. This design uses an open circuit wind tunnel with a low turbulence subsonic type, with a maximum air speed of 30 m/s. The exsisting wind tunnel still uses an analogue measuring instrument which is then modify in a digital arduino-based for drag and lift balance measuring instrument with a drag and lift sensor maximum load of 1kg (v=30m/s) and maximum air speed of 50m/s. The Measuring instrument is calibrated using a 1kg weight test equipment for testing with the test object model (spherical, hemispherical, cylindrical, cube) and three types of airfoil models. The test results are in the form of drag coefficient (C_d) and lift coefficient (C_L). The coefficient of drag is greatest in the cube shape and lowest in the sphere, but will decrease in value at a speed of 20 m/s. In the airfoil, the values ​​of C_d and C_L have the same trend with the literature with an uncertainty value of less than 10%. The value of C_L / C_d will increase as the angle of attack increases, but can very significantly depending on the fluid, airfoil, and aircraft type.

Abstract: Aerodynamic characteristics of three supermileage car chassis with new design concepts for improving the driver’s view field and driving comfort is investigated and compared with that of one with traditional low-height design. New car shapes with shorter axle distance and higher center of gravity are created. Feasibility of the new design is verified from the aspects of rollover safety, due to the maximum crosswind speed of 40 km/h, and the drag coefficient at straight driving up to 40 km/h. The analytical verification is conducted with a commercial CFD software. Comparing to the traditional design, the analysis shows that it is possible to obtain a lower drag coefficient and lower total drag, while rollover safety is still guaranteed, for a supermileage car with wider view field and taller appearance. Reduction of the form drag is intimately related to the decrease of velocity curl in the flow direction and the size of the vortices in the wake. Results of this study can provide new concepts that are different from those used in the past for the development of supermileage cars.

Abstract: Drag analysis is vital to measure the performance of the autonomous underwater vehicle (AUV) as well as the AUV thruster. Most of the previous drag studies is regarding to the shape and swimming method that contribute to the AUV performance. However, few attention was given on drag which influence the development of thruster. Hence, this research was conducted to analyze the drag of the micro AUV in a laminar fluid flow in order to find the optimum thrust that must be gained by a contractile water jet thruster (CWJT). Besides, these studies also focus on the dynamic pressure and skin friction that forms the total drag which acted on the AUV surface. Drag was measured by using pull technique and simulation technique for AUV speed below 0.5ms^-1. The results show that the recorded drag was between 9.0 x 10^-4N and 1.8 x 10^-1N. The trend line between the simulation data and experimental data has no significant difference and thus it shows that the simulation data were verified. Both results exhibits that the drag increase tremendously regarding to the AUV speed increment.

Abstract: Basketball players are taught to release the ball with a backward spin. This causes a lift due to the Magnus effect. Added to this there is a drag on the ball which always acts opposite to the direction of motion. In this paper, the trajectory of a basketball considering the lift and drag is calculated using numerical methods and also the force required to shoot the ball with different initial conditions from a distance of 25 feet away from a basket which is at a height of 10 feet is analyzed. A differential equation of motion of the ball in air is framed which accounts for all the forces on the ball. It is solved by discretizing the equation and solved using a C++ code. The trajectory of the balls with different initial conditions is plotted and it is found that as the spin on the ball increases, the effort required to shoot decreases.

Abstract: Dimple is a slight indentation in a surface. Dimples create turbulence by creating vortices which delays the boundary layer separation resulting in decrease of drag, increasing aerodynamic efficiency, manoeuvrability and also the angle of stall. The present work focused on the understanding of the effect of dimples on boundary layer separation, lift, drag, critical angle of attack, aerodynamic efficiency of wings. The airfoils without any dimples and with circular dimples as inward and outward on are studied. Types of dimples considered in 3D studies are circular and octagon dimple then computational analysis is done using ANSYS FLUENT CFD software, applying subsonic flow, in three dimensional co-ordinate system. The results are compared with a straight wing without dimples. Then suggestions and conclusions are made.

Abstract: Hydraulic orienter has been widely used to alter the drilling direction downhole in coiled tubing drilling. A problem is encountered in construction field. When torque and drag of bottom hole assembly (BHA) are over the maximum output torque of orienter, This caused that it difficult to orient. Therefore, we need to calculate the maximum torque and drag in the process of orientation, it can provide a theoretical basis for designing and selecting the hydraulic orienter. Compared with the conventional force analysis, this paper additionally considered the case of zero weight on bit (WOB), the impact of the mud viscous forces and the relationship between dynamic and static friction, so that we can get more precise result of force analysis.

Abstract: This paper is primarily concentrated with determining aerodynamic characteristics and choosing the best angle of attack at a maximum lift and low drag for the FX 63-137 aerofoil at a low Reynolds number and a speed of 20m/s and 30m/s, by using subsonic wind tunnel through manufacturing the aerofoil by aluminum alloy using a CNC machine. The proposed methodology is divided into several stages. Firstly, manufacturing the aerofoil using an aluminum alloy. Secondly, the testing process is carried out using subsonic wind tunnel. Thirdly, the results are displayed and compared with results produced from related works, in order to find out the best angle of attack at a maximum lift.

Abstract: In the present study, the aerodynamic characteristics such as time-averaged lift and drag generation of two flexible membrane (latex thin and thick) wings with different skin flexibilities are compared with those of a conventional rigid (wood) wing to assess the effects of skin flexibility (rigidity) on the aerodynamic performance for flapping flight applications. The experiments are performed in an open circuit wind tunnel of non-return airflow with a test section of (0.3m x 0.3m) and is capable of speeds from 0.5 to 30 m/s. The time-averaged lift and drag as functions of flapping frequency, forward flight velocity and the orientation angle of the flapping motions with respect to the incoming flows are measured by using a strain gauge balance and KYOWA PCD-300A sensor interface data acquisition system. It has been found that flapping motion would bring significant aerodynamic benefits when the flapping flight is in unsteady state regime, with advance ratio less than 1.0. The aerodynamic benefits are found to decay exponentially with the increasing advance ratio. Flapping motion is found to become detrimental for high speed flight applications. It is also observed that the skin flexibility has considerable effect on the aerodynamic performance. The flexible latex thick wing is found to have better overall aerodynamic performance over the rigid wing, especially for low speed applications. The wood (rigid) wing exhibited better lift production performance in quasi steady regime.

Abstract: The added mass, drag and drag coefficient of a uniform and accelerated motion projectile in viscous incompressible fluid were calculated by numerical simulation and dynamic mesh method. The effect of velocity and acceleration on the added mass, drag and drag coefficient of the projectile in a launch tube was investigated. The results show that the variation rules of added mass, drag and drag coefficient are basically the same when the projectile moves at different speeds. The added mass, drag and drag coefficient become smaller and drag becomes bigger with the increase of speed. The variation rules of the added mass, drag and drag coefficient are the same as uniform motion when the projectile moves at different accelerations. The added mass and drag coefficient become smaller and drag becomes bigger with the increase of acceleration. These reveal that the motion region, velocity and acceleration have some effect on the added mass, drag and drag coefficient.