After rising a short distance, the smooth column of smoke from a cigarette breaks up into an irregular and random pattern. In a similar fashion, a stream of fluid flowing past an obstacle breaks up into eddies and vortices which give the flow irregular ve

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Q: 18 (CDS-I/2012)
After rising a short distance, the smooth column of smoke from a cigarette breaks up into an irregular and random pattern. In a similar fashion, a stream of fluid flowing past an obstacle breaks up into eddies and vortices which give the flow irregular velocity components transverse to the flow direction. Other examples include the wakes left in water by moving ships, the sound produced by whistling and by wind instru- ments. These examples are the results of—

question_subject: 

Geography

question_exam: 

CDS-I

stats: 

0,14,16,5,9,14,2

keywords: 

{'turbulent flow': [0, 0, 0, 1], 'vortices': [0, 0, 0, 1], 'laminar flow': [0, 0, 0, 1], 'viscous flow': [0, 0, 0, 1], 'flow direction': [0, 0, 0, 1], 'irregular velocity components transverse': [0, 0, 0, 1], 'wind': [1, 0, 1, 2], 'flow': [0, 0, 1, 0], 'smoke': [4, 0, 0, 5], 'cigarette': [1, 0, 0, 1], 'air': [1, 0, 0, 0], 'random pattern': [0, 0, 0, 1], 'fluid': [1, 0, 1, 6], 'wakes': [0, 0, 0, 1], 'examples': [1, 0, 1, 5], 'stream': [1, 0, 1, 1], 'smooth column': [0, 0, 0, 1], 'other examples': [0, 0, 0, 1], 'sound': [4, 3, 10, 15]}

The correct answer is option 3: turbulent flow of air.

Turbulent flow is characterized by the chaotic and random movement of fluid particles. When a fluid flows past an obstacle, such as in the examples given (smoke from a cigarette, wakes left by moving ships, sound produced by whistling and wind instruments), the flow becomes turbulent. In this state, the fluid breaks up into eddies and vortices, which cause irregular velocity components transverse to the flow direction.

Option 1, laminar flow of air, refers to a smooth and regular flow of air where the fluid particles move in parallel layers. This option is incorrect because the question specifically mentions the smoke and water examples as being irregular and random.

Option 2, streamline flow of air, refers to a type of flow where the fluid particles follow predictable paths without mixing or crossing each other. This option is also incorrect because the question mentions the formation of eddies and vortices, which are not characteristic of streamline flow.

Option 4, viscous flow at low speed, refers to a flow where the fluid particles have high internal friction and move slowly. This option is incorrect because the question does not mention the speed or viscosity of the flow, only the irregular patterns formed.