Optimizing Lift By Different Number Of Spoke On Rotating Cylinder By Using CFD

Abstract

Nowadays, almost all aircraft design must be design to have the capability to produce high lift to drag ratio especially during the take-off to reduce drag and at the same time will increase the lift. Normally people would thought only the air foil shape can produce the lift but only few people will realize that rotating cylinder also can produce lift. However, the details of how a rotating cylinder creates lift are still quite complex. Next to any surface, the molecules of the air stick to the surface. This thin layer of molecules will entrain or pull the surrounding the airflow in the direction that the surface moves. If the rotating cylinder is put in rotating about longitudinal axis into a fluid, it would eventually create a spinning, vortex like flow around the cylinder. If the fluid is set into motion, the uniform velocity flow field can be added to the vortex flow. The net turning of the flow has produced an upward force. Because of the change to the velocity field, the pressure field will also be altered around the cylinder. Based on the previous research, which is the study of lift on rotating cylinder using different length of spokes, the data obtained obviously proving that vortex strength is somewhat directly proportional to the lift force. And of course the lift force is exponentially proportional to the airspeed. But the mass of air being pushed out of the spokes is the main criteria to have good lifting force. The result shows that the cylinder without spokes have negligible upward force but when added some spokes on the base cylinder, the lift improved almost immediately. And when double the length of the spokes, the lift went higher several folds. So this shows that the deeper the scoop, the more mass to make the air move faster at the topside of the cylinder, hence higher lift. But in terms of this research, the different number of spokes will be added to the rotating cylinder to compare which one produce highest lift. This will create vortex that will hasten the speed of air on top of the cylinder and at the same time retarding the speed of airflow below the cylinder. The airspeed, rpm, and the pressure created at the rotating cylinder will be the parameter to be measured to get the result from this experiment. So, lastly, which number of spokes create the most lift can be determined.