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Air flows past a golf bail of 20 mm radius. It is observed that the boundary layer becomes turbulent at Reynolds number of 2 x 105. If the kinematic viscosity of air is 1.5 x 10-5 m2/sec then the speed of air when the flow becomes turbulent is
- a)150 m/sec
- b)90m/seec
- c)75 m/sec
- d)62.5 m/sec
Correct answer is option 'C'. Can you explain this answer?
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Air flows past a golf bail of 20 mm radius. It is observed that the bo...
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Reynolds Number and Transition to Turbulent Flow:
The Reynolds number (Re) is a dimensionless quantity that characterizes the flow of a fluid. It is defined as the ratio of inertial forces to viscous forces and is given by the formula:
Re = (ρ * V * L) / μ
Where:
- ρ is the density of the fluid
- V is the velocity of the fluid
- L is a characteristic length of the flow (in this case, the diameter of the golf ball)
- μ is the dynamic viscosity of the fluid
When the Reynolds number is below a certain critical value, the flow is laminar, which means it is smooth and orderly. However, when the Reynolds number exceeds this critical value, the flow becomes turbulent, characterized by chaotic and unpredictable fluctuations.
Given Information:
- Radius of the golf ball (r) = 20 mm = 0.02 m
- Kinematic viscosity of air (ν) = 1.5 x 10^-5 m^2/s
- Critical Reynolds number for transition to turbulence (Re_critical) = 2 x 10^5
Calculating the Speed of Air:
To find the speed of air when the flow becomes turbulent, we need to rearrange the Reynolds number formula and solve for V:
Re = (ρ * V * L) / μ
V = (Re * μ) / (ρ * L)
Substituting the given values:
V = (2 x 10^5 * 1.5 x 10^-5) / (ρ * 0.04)
Now, we need to determine the density of air (ρ). At standard conditions (25°C and 1 atm), the density of air is approximately 1.184 kg/m^3.
V = (2 x 10^5 * 1.5 x 10^-5) / (1.184 * 0.04)
V ≈ 75 m/s
Therefore, the speed of air when the flow becomes turbulent is approximately 75 m/s, which corresponds to option C.
The Reynolds number (Re) is a dimensionless quantity that characterizes the flow of a fluid. It is defined as the ratio of inertial forces to viscous forces and is given by the formula:
Re = (ρ * V * L) / μ
Where:
- ρ is the density of the fluid
- V is the velocity of the fluid
- L is a characteristic length of the flow (in this case, the diameter of the golf ball)
- μ is the dynamic viscosity of the fluid
When the Reynolds number is below a certain critical value, the flow is laminar, which means it is smooth and orderly. However, when the Reynolds number exceeds this critical value, the flow becomes turbulent, characterized by chaotic and unpredictable fluctuations.
Given Information:
- Radius of the golf ball (r) = 20 mm = 0.02 m
- Kinematic viscosity of air (ν) = 1.5 x 10^-5 m^2/s
- Critical Reynolds number for transition to turbulence (Re_critical) = 2 x 10^5
Calculating the Speed of Air:
To find the speed of air when the flow becomes turbulent, we need to rearrange the Reynolds number formula and solve for V:
Re = (ρ * V * L) / μ
V = (Re * μ) / (ρ * L)
Substituting the given values:
V = (2 x 10^5 * 1.5 x 10^-5) / (ρ * 0.04)
Now, we need to determine the density of air (ρ). At standard conditions (25°C and 1 atm), the density of air is approximately 1.184 kg/m^3.
V = (2 x 10^5 * 1.5 x 10^-5) / (1.184 * 0.04)
V ≈ 75 m/s
Therefore, the speed of air when the flow becomes turbulent is approximately 75 m/s, which corresponds to option C.
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Air flows past a golf bail of 20 mm radius. It is observed that the boundary layer becomes turbulent at Reynolds number of 2 x 105. If the kinematic viscosity of air is 1.5 x 10-5 m2/sec then the speed of air when the flow becomes turbulent isa)150 m/secb)90m/seecc)75 m/secd)62.5 m/secCorrect answer is option 'C'. Can you explain this answer?
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Air flows past a golf bail of 20 mm radius. It is observed that the boundary layer becomes turbulent at Reynolds number of 2 x 105. If the kinematic viscosity of air is 1.5 x 10-5 m2/sec then the speed of air when the flow becomes turbulent isa)150 m/secb)90m/seecc)75 m/secd)62.5 m/secCorrect answer is option 'C'. Can you explain this answer? for Mechanical Engineering 2025 is part of Mechanical Engineering preparation. The Question and answers have been prepared according to the Mechanical Engineering exam syllabus. Information about Air flows past a golf bail of 20 mm radius. It is observed that the boundary layer becomes turbulent at Reynolds number of 2 x 105. If the kinematic viscosity of air is 1.5 x 10-5 m2/sec then the speed of air when the flow becomes turbulent isa)150 m/secb)90m/seecc)75 m/secd)62.5 m/secCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for Mechanical Engineering 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Air flows past a golf bail of 20 mm radius. It is observed that the boundary layer becomes turbulent at Reynolds number of 2 x 105. If the kinematic viscosity of air is 1.5 x 10-5 m2/sec then the speed of air when the flow becomes turbulent isa)150 m/secb)90m/seecc)75 m/secd)62.5 m/secCorrect answer is option 'C'. Can you explain this answer?.
Air flows past a golf bail of 20 mm radius. It is observed that the boundary layer becomes turbulent at Reynolds number of 2 x 105. If the kinematic viscosity of air is 1.5 x 10-5 m2/sec then the speed of air when the flow becomes turbulent isa)150 m/secb)90m/seecc)75 m/secd)62.5 m/secCorrect answer is option 'C'. Can you explain this answer? for Mechanical Engineering 2025 is part of Mechanical Engineering preparation. The Question and answers have been prepared according to the Mechanical Engineering exam syllabus. Information about Air flows past a golf bail of 20 mm radius. It is observed that the boundary layer becomes turbulent at Reynolds number of 2 x 105. If the kinematic viscosity of air is 1.5 x 10-5 m2/sec then the speed of air when the flow becomes turbulent isa)150 m/secb)90m/seecc)75 m/secd)62.5 m/secCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for Mechanical Engineering 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Air flows past a golf bail of 20 mm radius. It is observed that the boundary layer becomes turbulent at Reynolds number of 2 x 105. If the kinematic viscosity of air is 1.5 x 10-5 m2/sec then the speed of air when the flow becomes turbulent isa)150 m/secb)90m/seecc)75 m/secd)62.5 m/secCorrect answer is option 'C'. Can you explain this answer?.
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Air flows past a golf bail of 20 mm radius. It is observed that the boundary layer becomes turbulent at Reynolds number of 2 x 105. If the kinematic viscosity of air is 1.5 x 10-5 m2/sec then the speed of air when the flow becomes turbulent isa)150 m/secb)90m/seecc)75 m/secd)62.5 m/secCorrect answer is option 'C'. Can you explain this answer?, a detailed solution for Air flows past a golf bail of 20 mm radius. It is observed that the boundary layer becomes turbulent at Reynolds number of 2 x 105. If the kinematic viscosity of air is 1.5 x 10-5 m2/sec then the speed of air when the flow becomes turbulent isa)150 m/secb)90m/seecc)75 m/secd)62.5 m/secCorrect answer is option 'C'. Can you explain this answer? has been provided alongside types of Air flows past a golf bail of 20 mm radius. It is observed that the boundary layer becomes turbulent at Reynolds number of 2 x 105. If the kinematic viscosity of air is 1.5 x 10-5 m2/sec then the speed of air when the flow becomes turbulent isa)150 m/secb)90m/seecc)75 m/secd)62.5 m/secCorrect answer is option 'C'. Can you explain this answer? theory, EduRev gives you an
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