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During the flow over a circular cylinder, the drag coefficient dropssignificantly at a critical Reynolds number of 2 × 105. This is due to
- a)Excessive momentum loss in the boundary layer
- b)Separation point travelling upstream
- c)Reduction in skin-friction drag
- d)The delay in separation due to transition to turbulence
Correct answer is option 'D'. Can you explain this answer?
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Verified Answer
During the flow over a circular cylinder, the drag coefficient dropssi...
Ans. (d) The drag co-efficient remains practically constant unit a Reynold’s number of 2 × 105 is reached. At this stage the Cd drops steeply by a factor of 5.
This is due to the fact that the laminar boundary layer turns turbulent and stays unseparated over a longer distance, then reducing the wake considerably.
This is due to the fact that the laminar boundary layer turns turbulent and stays unseparated over a longer distance, then reducing the wake considerably.
Most Upvoted Answer
During the flow over a circular cylinder, the drag coefficient dropssi...
Explanation:
The phenomenon of a drop in drag coefficient at a critical Reynolds number of 2x10^5 during the flow over a circular cylinder is known as the Karman vortex street.
Karman vortex street:
- When a fluid flows past a cylindrical body, flow separation occurs at the rear end creating vortices.
- At low Reynolds numbers, these vortices are shed in an irregular and unpredictable manner.
- As the Reynolds number increases, the shedding becomes regular and periodic, leading to the formation of a series of vortices that alternate in a pattern known as the Karman vortex street.
- This pattern of vortices is responsible for the drop in drag coefficient at the critical Reynolds number.
Delay in separation due to transition to turbulence:
- The transition to turbulence delays the separation of the boundary layer from the cylinder surface.
- This delay causes the formation of smaller vortices in the wake of the cylinder, which reduces the size of the larger vortices.
- The reduction in the size of the vortices leads to a reduction in the drag coefficient.
Conclusion:
Therefore, the correct option is D, i.e., the delay in separation due to transition to turbulence.
The phenomenon of a drop in drag coefficient at a critical Reynolds number of 2x10^5 during the flow over a circular cylinder is known as the Karman vortex street.
Karman vortex street:
- When a fluid flows past a cylindrical body, flow separation occurs at the rear end creating vortices.
- At low Reynolds numbers, these vortices are shed in an irregular and unpredictable manner.
- As the Reynolds number increases, the shedding becomes regular and periodic, leading to the formation of a series of vortices that alternate in a pattern known as the Karman vortex street.
- This pattern of vortices is responsible for the drop in drag coefficient at the critical Reynolds number.
Delay in separation due to transition to turbulence:
- The transition to turbulence delays the separation of the boundary layer from the cylinder surface.
- This delay causes the formation of smaller vortices in the wake of the cylinder, which reduces the size of the larger vortices.
- The reduction in the size of the vortices leads to a reduction in the drag coefficient.
Conclusion:
Therefore, the correct option is D, i.e., the delay in separation due to transition to turbulence.
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During the flow over a circular cylinder, the drag coefficient dropssignificantly at a critical Reynolds number of 2 × 105. This is due toa)Excessive momentum loss in the boundary layerb)Separation point travelling upstreamc)Reduction in skin-friction dragd)The delay in separation due to transition to turbulenceCorrect answer is option 'D'. Can you explain this answer?
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During the flow over a circular cylinder, the drag coefficient dropssignificantly at a critical Reynolds number of 2 × 105. This is due toa)Excessive momentum loss in the boundary layerb)Separation point travelling upstreamc)Reduction in skin-friction dragd)The delay in separation due to transition to turbulenceCorrect answer is option 'D'. Can you explain this answer? for Mechanical Engineering 2024 is part of Mechanical Engineering preparation. The Question and answers have been prepared according to the Mechanical Engineering exam syllabus. Information about During the flow over a circular cylinder, the drag coefficient dropssignificantly at a critical Reynolds number of 2 × 105. This is due toa)Excessive momentum loss in the boundary layerb)Separation point travelling upstreamc)Reduction in skin-friction dragd)The delay in separation due to transition to turbulenceCorrect answer is option 'D'. Can you explain this answer? covers all topics & solutions for Mechanical Engineering 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for During the flow over a circular cylinder, the drag coefficient dropssignificantly at a critical Reynolds number of 2 × 105. This is due toa)Excessive momentum loss in the boundary layerb)Separation point travelling upstreamc)Reduction in skin-friction dragd)The delay in separation due to transition to turbulenceCorrect answer is option 'D'. Can you explain this answer?.
During the flow over a circular cylinder, the drag coefficient dropssignificantly at a critical Reynolds number of 2 × 105. This is due toa)Excessive momentum loss in the boundary layerb)Separation point travelling upstreamc)Reduction in skin-friction dragd)The delay in separation due to transition to turbulenceCorrect answer is option 'D'. Can you explain this answer? for Mechanical Engineering 2024 is part of Mechanical Engineering preparation. The Question and answers have been prepared according to the Mechanical Engineering exam syllabus. Information about During the flow over a circular cylinder, the drag coefficient dropssignificantly at a critical Reynolds number of 2 × 105. This is due toa)Excessive momentum loss in the boundary layerb)Separation point travelling upstreamc)Reduction in skin-friction dragd)The delay in separation due to transition to turbulenceCorrect answer is option 'D'. Can you explain this answer? covers all topics & solutions for Mechanical Engineering 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for During the flow over a circular cylinder, the drag coefficient dropssignificantly at a critical Reynolds number of 2 × 105. This is due toa)Excessive momentum loss in the boundary layerb)Separation point travelling upstreamc)Reduction in skin-friction dragd)The delay in separation due to transition to turbulenceCorrect answer is option 'D'. Can you explain this answer?.
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