GATE-CH-1993-9-c-fm-2mark

Match the following: The shear stress vs. velocity gradient characteristics are shown in figure.

• I.

Answer 1C. Bingham plasticB. DilatantD. Pseudo plasticA. Newtonian

• II.

Answer 2C. Bingham plasticB. DilatantD. Pseudo plasticA. Newtonian

• III.

Answer 3C. Bingham plasticB. DilatantD. Pseudo plasticA. Newtonian

• IV.

Answer 4C. Bingham plasticB. DilatantD. Pseudo plasticA. Newtonian

GATE-CH-1988-2-ii-fm-1mark

For pseudoplastic fluids, increase in shear rate

• increases the apparent viscosity

• decreases the apparent viscosity

• has no effect on apparent viscosity

• has unspecified effect

GATE-CH-1989-2-i-c-fm-1mark

For a dilatant fluid, the magnitude of the slope of the shear stress versus the velocity gradient curve ––––- with increasing velocity gradient.

• increases

• decreases

• remains unchanged

• may decrease or increase

GATE-CH-1994-1-j-fm-1mark

The shear stress–shear rate relationship for a liquid whose apparent viscosity decreases with increasing shear rate is given by

• \(\displaystyle \tau _{yx} = -m\left [\frac {dv_x}{dy}\right ]^{n-1}\frac {dv_x}{dy}\) for \(n <1\)
  

• \(\displaystyle \tau _{yx} = -m\left [\frac {dv_x}{dy}\right ]^{n}\) for \(n =1\)
  

• \(\displaystyle \tau _{yx} = -m\left [\frac {dv_x}{dy}\right ]^{n-1}\frac {dv_x}{dy}\) for \(n >1\)
  

• \(\displaystyle \tau _{yx} = -m\frac {dv_x}{dy} + \tau _o\)

GATE-CH-2001-2-6-fm-2mark

A Bingham fluid of viscosity \(\mu \) = 10 Pa.s, and yield stress \(\tau _o\) = 10 kPa, is sheared between flat parallel plates separated by a distance 10\(^{-3}\) m. The top plate is moving with a velocity of 1 m/s. The shear stress on the plate is

• 10 kPa

• 20 kPa

• 30 kPa

• 40 kPa

GATE-CH-2003-10-fm-1mark

A lubricant 100 times more viscous than water would have a viscosity (in Pa.s)

• 0.01

• 0.1

• 1

• 10

GATE-CH-2004-49-fm-2mark

Viscosity of water at 40^oC lies in the range of

• \(1\times 10^{-3}\) - \(2\times 10^{-3}\) kg/(m.s)

• \(0.5 \times 10^{-3}\) - \(1 \times 10^{-3}\) kg/(m.s)

• 1 - 2 kg/(m.s)

• 0.5 - 1 kg/(m.s)

GATE-CH-2005-12-fm-1mark

Match the following types of fluid (in group I) with their respective constitutive relations (in group II), where \(\tau \) is the stress and \(\dot {\gamma }\) is the strain rate.

Group I	Group II
(P) Pseudoplastic	(I) \(\tau = \mu \dot {\gamma }\)
(Q) Bingham plastic	(II) \(\tau = \tau _o + K\dot {\gamma }\)
	(III) \(\tau = K|\dot {\gamma }|^n; \quad n < 1\)
	(IV) \(\tau = K|\dot {\gamma }|^n; \quad n > 1\)

• P-I, Q-IV

• P-IV, Q-I

• P-II, Q-III

• P-III, Q-II

GATE-CH-2006-38-fm-2mark

A fluid obeying the constitutive equation \[ \tau = \tau _o + K \left (\frac {dv_x}{dy}\right )^{\frac {1}{2}}, \quad \tau > \tau _o \] is held between two parallel plates a distance \(d\) apart. If the stress applied to the top plate is \(3\tau _o\), then the velocity with which the top plate moves relative to the bottom plate would be

• \(\displaystyle 2 \left (\frac {\tau _o}{K}\right )^2d\)

• \(\displaystyle 3 \left (\frac {\tau _o}{K}\right )^2d\)

• \(\displaystyle 4 \left (\frac {\tau _o}{K}\right )^2d\)

• \(\displaystyle 9 \left (\frac {\tau _o}{K}\right )^2d\)

GATE-CH-2013-10-fm-1mark

The apparent viscosity of a fluid is given by \(0.007 \left (\dfrac {dV}{dy}\right )^{0.3}\) where \(\left (\dfrac {dV}{dy}\right )\) is the velocity gradient. The fluid is

• Bingham plastic

• dilatant

• pseudoplastic

• thixotropic

GATE-CH-2014-13-fm-1mark

Which of the following statements are CORRECT?

• [P.] For a rheopectic fluid, the apparent viscosity increases with time under a constant applied shear stress
• [Q.] For a pseudoplastic fluid, the apparent viscosity decreases with time under a constant applied shear stress
• [R.] For a Bingham plastic, the apparent viscosity increases exponentially with the deformation rate
• [S.] For a dilatant fluid, the apparent viscosity increases with increasing deformation rate

• P and Q only

• Q and R only

• R and S only

• P and S only

GATE-XE-2012-B-14-fm-2mark

The figure given below shows typical non-dimensional velocity profiles for fully developed laminar flow between two infinitely long parallel plates separated by a distance \(a\) along \(y\)-direction. The upper plate is moving with a constant velocity \(U\) in the \(x\)-direction and the lower plate is stationary.

Match the non-dimensional velocity profiles in column I with the pressure gradients in column II.

Column I	Column II
P. profile I	1. \(\dfrac {\partial P}{\partial x} > 0\)
Q. profile II	2. \(\dfrac {\partial P}{\partial x} < 0\)
R. profile III	3. \(\dfrac {\partial P}{\partial x} = 0\)

• P-2; Q-3; R-1

• P-3; Q-2; R-1

• P-3; Q-1; R-2

• P-1; Q-2; R-3

GATE-CH-2012-52-53-fm-4mark

A Newtonian fluid of viscosity \(\mu \) flows between two parallel plates due to the motion of the bottom plate (as shown below), which is moved with a velocity \(V\). The top plate is stationary.

(i) The steady, laminar velocity profile in the \(x\)-direction is

{#1}

(ii) The force per unit unit area (in the \(x\)-direction) that must be exerted on the bottom plate to maintain the flow is

{#2}