FLUID STATICS AND DYNAMICS (IN 1001) Flashcards
(31 cards)
Which statement is true for a fluid?
(A) It cannot sustain a shear force.
(B) It cannot sustain a shear force at rest.
(C) It is a liquid only.
(D) It has a very regular molecular structure.
(B) It cannot sustain a shear force at rest.
Which of the following is NOT a basic component of motion of a fluid element?
(A) translation
(B) rotation
(C) angular distortion
(D) twist
(D) twist
Which of the following must be satisfied by the flow of any fluid, real or ideal?
I. Newton’s second law of motion
II. The continuity equation
III. The requirement of a uniform velocity distribution
IV. Newton’s law of viscosity
V. The principle of conservation of energy
(A) I, II, and III
(B) I, II, and IV
(C) I, II, and V
(D) I, II, III, and IV
(C) I, II, and V
What is the definition of pressure?
(A) area / force
(B) lim force → 0 (force / area)
(C) lim area → 0 (force / area)
(D) lim force → 0 (area / force)
(C) lim area → 0 (force / area)
For a fluid, viscosity is defined as the constant of proportionality between shear stress and what other variable?
(A) time derivative of pressure
(B) time derivative of density
(C) spatial derivative of velocity
(D) spatial derivative of density
(C) spatial derivative of velocity
Surface tension has which of the following properties?
I. It has units of force per unit length.
II. It exists whenever there is a density discontinuity.
III. It is strongly affected by pressure.
(A) I only
(B) II only
(C) III only
(D) I and II
(D) I and II
A leak from a faucet comes out in separate drops. Which of the following is the main cause of this phenomenon?
(A) gravity
(B) air resistance
(C) viscosity of the fluid
(D) surface tension
(D) surface tension
Which of the following describes shear stress in a moving Newtonian fluid?
(A) It is proportional to the absolute viscosity.
(B) It is proportional to the velocity gradient at the point of interest.
(C) It is nonexistent
(D) both A and B
(D) both A and B
If the shear stress in a fluid varies linearly with the velocity gradient, which of the following describes the fluid?
(A) It is inviscid
(B) It is a perfect gas.
(C) It is at a Newtonian fluid.
(D) It is at a constant temperature.
(C) It is at a Newtonian fluid.
How are lines of constant pressure in a fluid related to the force field?
(A) They are parallel to the force field.
(B) They are perpendicular to the force field.
(C) They are at a 45° angle to the force field.
(D) They are perpendicular only to the force of gravity.
(B) They are perpendicular to the force field.
Which of the following statements about a streamline is most accurate?
(A) It is a path of a fluid particle
(B) It is a line normal to the velocity vector everywhere.
(C) It is fixed in space in steady flow.
(D) It is defined for nonuniform flow only.
(C) It is fixed in space in steady flow.
Which of the following describes a streamline?
I. It is a mathematical concept.
II. It cannot be crossed by the flow.
III. It is a line of constant entropy.
(A) I only
(B) II only
(C) I and II
(D) I and III
(C) I and II
The stream potential, Φ, of a flow is given by Φ = 2xy-y. Determine the stream function, Ψ, for this potential.
(A) Ψ = x² - y² + C
(B) Ψ = x - x² + y² + C
(C) Ψ = x + x² - y² + C
(D) Ψ = x² + y² + C
(B) Ψ = x - x² + y² + C
Determine the average velocity through a circular section in which the velocity distribution is given as v = vₘₐₓ(1 - (r/rₒ)²). The distribution is symmetric with respect to the longitudinal axis, r = 0. rₒ is the outer radius and vₘₐₓ is the velocity along the longitudinal axis.
(A) vₘₐₓ/4
(B) vₘₐₓ/3
(C) vₘₐₓ/2
(D) vₘₐₓ
vₘₐₓ/2
Under what conditions is mass conserved in fluid flow?
(A) The fluid is baratropic.
(B) The flow is isentropic.
(C) The flow is adiabatic.
(D) It is always conserved.
(D) It is always conserved.
What is the absolute velocity of a real fluid at a surface?
(A) the same as the bulk fluid velocity
(B) the velocity of the surface
(C) zero
(D) proportional to the smoothness of the surface
(B) the velocity of the surface
which of the statements is true concerning the following continuity equation?
∂p / ∂t + ∂(pu) / ∂x + ∂(pv) / ∂y + ∂(pw) / ∂z = 0
p is the density, u is the velocity in the x direction, v is velocity in the y direction, and w is velocity in the z direction.
(A) It is valid only for incompressible flow.
(B) It is valid only for steady flow.
(C) It is derived from the principle of conservation of mass.
(D) It is derived from the principle of conservation of energy.
(C) It is derived from the principle of conservation of mass.
Which of the following sets of dimensional flow equations satisfies the continuity equation? (u, v, and w are the components of velocity in the x, y, and z directions, respectively.)
I. u = x + 2y - t
v = t - 2y + z
w = t - 2x + z
II. u = y² - x²
v = 2xy
w = 2tz
III. u = x² - y²
v = -2xy + ty
w = -tz
(A) I and II
(B) I and III
(C) II and III
(D) I, II, and III
(B) I and III
What is the origin of the energy conservation equation used in flow systems?
(A) Newton’s first law of motion
(B) Newton’s second law of motion
(C) the first law of thermodynamics
(D) the second law of thermodynamics
(C) the first law of thermodynamics
Which of the following is the basis for Bernoulli’s law for fluid flow?
(A) the principle of conservation of mass
(B) the principle of conservation of energy
(C) the continuity equation
(D) the principle of conservation of momentum
(B) the principle of conservation of energy
Under which of the following conditions is Bernoulli’s equation valid?
(A) all points evaluated must be on the same streamline
(B) the fluid must be incompressible
(C) the fluid must be inviscid
(D) all of the above
(D) all of the above
Under certain flow conditions, the expression for the first law of thermodynamics for a control volume reduces to Bernoulli’s equation.
gz₁ + (v₁² / 2) + p₁/p = gz₂ + (v₂² / 2) + p₂ / p
Which combination of the following conditions is necessary and sufficient to reduce the first law of thermodynamics for a control volume to Bernoulli’s equation?
I. steady flow
II. incompressible fluid
III. no frictional losses of energy
IV. no heat transfer or change in internal energy
(A) I only
(B) I and II
(C) I and IV
(D) I, II, III, and IV
(D) I, II, III, and IV
What are the units of Reynolds number for pipe flow?
(A) m/s
(B) m²/s
(C) kg / ms²
(D) none of the above
(D) none of the above
Which of the following ratios represents a physical interpretation of the Reynolds number?
(A) Re = (buoyant forces / inertial forces)
(B) Re = (viscous forces / inertial forces)
(C) Re = (drag forces / viscous forces)
(D) Re = (inertial forces / viscous forces)
(D) Re = (inertial forces / viscous forces)
