MCQOPTIONS
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MCQOPTIONS
This section includes 19 Mcqs, each offering curated multiple-choice questions to sharpen your Fluid Mechanics knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Change in boundary layer from laminar to turbulent is directly affected by(i) Roughness of plate(ii) Pressure gradient(iii) Intensity of turbulence(iv) Velocity of flowWhich of the above-mentioned option(s) is/are incorrect? |
| A. | (i) and (iii) |
| B. | (ii) and (iv) |
| C. | Only (iii) |
| D. | Only (iv) |
| Answer» E. | |
| 2. |
Momentum thickness is given by |
| A. | \(\mathop \smallint \nolimits_0^\delta \left( {1 - \frac{u}{U}} \right)dy\) |
| B. | \(\mathop \smallint \nolimits_0^\delta \frac{u}{U}\left( {1 - \frac{u}{U}} \right)dy\) |
| C. | \(\mathop \smallint \nolimits_0^\delta \frac{u}{U}\left( {1 - \frac{{{u^2}}}{{{U^2}}}} \right)dy\) |
| D. | \(\mathop \smallint \nolimits_0^\delta \frac{{{u^2}}}{{{U^2}}}\left( {1 - \frac{{{u^2}}}{{{U^2}}}} \right)dy\) |
| Answer» C. \(\mathop \smallint \nolimits_0^\delta \frac{u}{U}\left( {1 - \frac{{{u^2}}}{{{U^2}}}} \right)dy\) | |
| 3. |
Consider the following statements pertaining to boundary layer on a flat plate:1. The thickness of laminar boundary layer at a distance x from the leading edge varies as x1/22. The thickness of turbulent boundary layer at a distance x from the leading edge varies as x4/5 3. Boundary layer is laminar when Reynolds number is less than 5 x 105Which of the above statements are correct? |
| A. | 1, 2 and 3 |
| B. | 1 and 2 only |
| C. | 1 and 3 only |
| D. | 2 and 3 only |
| Answer» B. 1 and 2 only | |
| 4. |
Match the following List-I List-II ACompressible flow1Reynolds numberBFree surface flow2Nusselt numberCBoundary layer flow3Weber numberDPipe flow4Froude numberEHeat convection5Mach number 6Skin friction coefficient |
| A. | A - 1, B - 4, C - 2, D - 6; E - 3 |
| B. | A - 3, B - 4, C - 6, D - 1; E - 2 |
| C. | A - 5, B - 3, C - 6, D - 1; E - 4 |
| D. | A - 5, B - 3, C - 6, D - 1; E - 2 |
| Answer» E. | |
| 5. |
Consider the following statements pertaining to boundary layer on solid surfaces:1) The boundary layer separation takes place if the pressure gradient is zero.2) The condition of boundary layer separation is \({\left( {\frac{{\delta u}}{{\delta y}}} \right)_{y = 0}} = 0\)3) Boundary layer on a flat plate is laminar if the Reynolds number is less than 5 × 105Which of the above statements is/are correct? |
| A. | 1, 2 and 3 |
| B. | 1 and 2 only |
| C. | 2 and 3 only |
| D. | 1 and 3 only |
| Answer» D. 1 and 3 only | |
| 6. |
In a turbulent pipe flow, the velocity distribution inside a boundary layer is |
| A. | Linear |
| B. | Parabolic |
| C. | Logarithmic |
| D. | According to prandlt’s one-seventh power law |
| Answer» E. | |
| 7. |
A smooth flat plate with a sharp leading edge is placed along a free stream of water flowing at 2.5 m/sec. At what distance from the leading edge will the boundary layer transition from laminar to turbulent flow? Take density of water as 1000 kg/m3 and its viscosity as 1 centipoise. Also, what will be the boundary layer thickness at that distance? (Assume Rec = 3.2 × 105) |
| A. | 12.8 cm and 0.113 cm |
| B. | 14.2 cm and 0.113 cm |
| C. | 12.8 cm and 0.125 cm |
| D. | 14.2 cm and 0.125 cm |
| Answer» B. 14.2 cm and 0.113 cm | |
| 8. |
A transmitter antenna is of a vertical pipe, 20 cm diameter and 25 m in height, on top of a tall structure. It is subjected to wind speed of 20 m/sec. Density of air is 1.22 kg/m3; its viscosity is 1.8 x 10-5 Ns/m2. Drag coefficient of a (tall) circular cylinder is tabulated as Re 102 103 1.3 × 103 104 1.5 × 104 1.06 × 105 1.2 × 105 4.5 × 105 CD1.61.050.951.01.081.00.890.26What is the drag experienced? |
| A. | 737 N |
| B. | 700 N |
| C. | 670 N |
| D. | 63 N |
| Answer» B. 700 N | |
| 9. |
Bluff body surface _______. |
| A. | is smooth so that friction can be neglected |
| B. | Coincides with streamlines |
| C. | Does not coincide with streamlines |
| D. | Perpendicular to streamlines |
| Answer» D. Perpendicular to streamlines | |
| 10. |
Drag force is a function of _____ |
| A. | projected area of the body |
| B. | mass density of the fluid |
| C. | velocity of the body |
| D. | All options are correct |
| Answer» E. | |
| 11. |
Friction drag is generally larger than the pressure drag in _______. |
| A. | Flow past a sphere |
| B. | Flow past a cylinder |
| C. | Flow past an airfoil |
| D. | Flow past a thin sheet |
| Answer» D. Flow past a thin sheet | |
| 12. |
If a thin plate is held parallel to fluid stream the pressure drag on it is: |
| A. | Maximum |
| B. | Minimum |
| C. | Zero |
| D. | None of these |
| Answer» D. None of these | |
| 13. |
Pressure drag results due to |
| A. | Turbulent in the wake |
| B. | Formation of wake |
| C. | Existence of stagnation point in the front of the body |
| D. | High Reynold’s number |
| Answer» C. Existence of stagnation point in the front of the body | |
| 14. |
Bluff body is the body of such a shape that pressure drag as compared to friction drag is |
| A. | same |
| B. | more |
| C. | less |
| D. | zero |
| Answer» C. less | |
| 15. |
Boundary-Layer Thickness(δ) is the distance from the surface of the solid body in the direction perpendicular to flow, where the velocity of the fluid is equal to: |
| A. | Free stream velocity |
| B. | 1.2 times the free stream velocity |
| C. | 0.99 times the free stream velocity |
| D. | None of the above |
| Answer» D. None of the above | |
| 16. |
A streamlined body is defined as a body about which ________. |
| A. | The flow is laminar |
| B. | The flow is along the stream lines |
| C. | The flow separation is suppressed |
| D. | The drag is zero |
| Answer» D. The drag is zero | |
| 17. |
Boundary layer is defined as |
| A. | A thin layer at the surface where gradients of both velocity and temperature are small |
| B. | A thin layer at the surface where velocity and velocity gradients are large |
| C. | A thick layer at the surface where velocity and temperature gradients are large |
| D. | A thin layer at the surface where gradients of both velocity and temperature are large |
| Answer» E. | |
| 18. |
In a laminar and turbulent boundary layer over the entire length of plate, the boundary layer thickeners at a distance x from leading edge varies respectively as |
| A. | \({x^{\frac{1}{2}}},\;{x^{\frac{1}{5}}}\) |
| B. | \({x^2},\;{x^{\frac{1}{7}}}\) |
| C. | \({x^{\frac{4}{5}}},\;{x^{\frac{1}{2}}}\) |
| D. | \({x^{\frac{1}{2}}},\;{x^{\frac{4}{5}}}\) |
| Answer» E. | |
| 19. |
If δ1 and δ2 are the laminar boundary layer thicknesses at a point M distant x from the leading edge when the Reynolds number of the flow are 100 and 484, respectively, then the ratio δ1/δ2 will be |
| A. | 2.2 |
| B. | 4.84 |
| C. | 23.43 |
| D. | 45.45 |
| Answer» B. 4.84 | |