Fluid Mechanics 230 - Essay Example

TYPES OF DRAG Form drag This could be described as the frictional force resulting from the shape of a moving object. This drag remains highly dependent on size and shape of objects; hence, the name form drag (Batchelor 2000). Bodies with larger cross-sectional designs experience higher levels of form drag than those presented with sleek design. The shape and size of a body affects the surface area of the object which comes into contact with the fluid. The experienced frictional forces results from contact between the moving object and fluid through which movement occurs.

The occurrence of this drag depends on the object shape, large cross-sectional designs offers higher percentage of object contact with fluid, frictional forces inducing higher levels of form drag. Skin friction Skins friction refers to a type of drag resulting from frictional forces existing between the skin of objects and the fluid through which movement occurs. This drag arises from interaction between fluids and object surface, and remains dependent on wetted surface area when addressing occurrence within marine vehicles.

This frictional force remains directly proportional to the surface area of the object’s skin contacting the fluid. The frictional force also follows the drag equation making it a coefficient of prevailing square of marine vehicle speed. Fluid viscosity, resulting from friction between neighbouring parcels of fluid moving in a different direction, contributes to the occurrence of viscous drag. Viscous drag, consequently, contributes to the development of skin friction within marine vehicles.

Interference drag This could be defined as drag caused by flow interference experienced at structural junctions of objects moving within fluids. The experienced interference ultimately contributes to increased pressure upon other parts of the surface contacting fluids, consequently increasing the overall drag effect. While all objects experience certain levels of drag, when moving within fluids, the presence of junctions upon the structure increases the overall drag experienced by objects. Interference drag remains characteristic of objects having transonic flow.

Objects moving at high speeds nearing 700 miles per hour commonly experience interference drag related to the travelling speeds nearing those of sound. The surrounding fluid speeds normally affect the occurrence of interference drag. When fluids move in the opposite direction, the resulting speed experienced at the contact increases significantly, and could contribute to the occurrence of interference drag in objects moving at slower speeds. Lift-induced drag This could become defined as drag resulting from the redirection of airflow by moving objects towards a different direction.

In moving marine vessels this drag normally results from flowing air inducing a lifting characteristic upon the marine vehicles. Lift-induced drag within marine vehicles occurs on vessels moving on water. Vessels moving underwater, like submarines, cannot experience this drag force because it becomes induced through air. Underwater vessels only remain in contact with water. These marine vehicles never come into contact with air as they travel submerged underwater. When vessels travel at increased speeds on water, the influence of air affects the motion through inducing a lifting motion upon marine vessels.

The lift normally occurs following substantial changes in speed and direction of flowing wind. While vessels might remain travelling