Discussion
For a two-dimensional incompressible flow over a flat plate, the laminar boundary layer thickness at a distance \(x\) from the leading edge is \(\delta\). If \(Re_{x}\) is the Reynolds number defined based on length scale x, \(\left(\dfrac{\delta}{x}\right)\) is proportional to ______.
Answer: A
\(\delta/x\) is proportional to \(Re_{x}^{-1/2}\).
For a laminar boundary layer on a flat plate, the Blasius solution gives
\[ \frac{\delta}{x} \approx \frac{5.0}{\sqrt{Re_{x}}} \]
The scaling follows from balancing inertia, \(U^{2}/x\), with viscous diffusion, \(\nu U/\delta^{2}\), which gives \(\delta \sim \sqrt{\nu x/U}\). So the boundary layer grows as \(\sqrt{x}\) and \(\delta/x\) falls as \(Re_{x}^{-1/2}\). The exponent −1/5 belongs to the turbulent boundary layer; −1, −3/2 and −2 do not arise for either.
Post your comment
Please log in or register to post a comment.
Examination Categories
- SSC Exams
- Banking Exams
- Teaching Exams
- Civil Services Exams
- Railways Exams
- Engineering Recruitment Exams
- Defence Exams
- State Government Exams
- Police Exams
- Insurance Exams
- Nursing Exams
- Other Government Exams
- NRA CET
- PG Entrance Exams
- Campus Placement
- MBA Entrance Exams
- CUET and UG Entrance
- Judiciary Exams
- Regulatory Body Exams
- Software Development