A very small circular cylinder of radius R t is rotating angular velocity ω i , inside a much larger concentric cylinder of radius R 0 that is rotating at angular velocity ω 0 . A liquid of density ρ and viscosity μ is confined between the two cylinders, as in Fig. P4-41. Gravitational and end effects can be neglected (the flow is two-dimensional into the page). If ω j = ω 0 and a long time has passed. generate an expression for the tangential velocity profile. u θ as a function of (at most) r , ω , R j , R o , ρ . and μ . where ω = ω 1 = ω 0 . Also, calculate the torque exerted by the fluid on the inner cylinder and on the outer cylinder.
A very small circular cylinder of radius R t is rotating angular velocity ω i , inside a much larger concentric cylinder of radius R 0 that is rotating at angular velocity ω 0 . A liquid of density ρ and viscosity μ is confined between the two cylinders, as in Fig. P4-41. Gravitational and end effects can be neglected (the flow is two-dimensional into the page). If ω j = ω 0 and a long time has passed. generate an expression for the tangential velocity profile. u θ as a function of (at most) r , ω , R j , R o , ρ . and μ . where ω = ω 1 = ω 0 . Also, calculate the torque exerted by the fluid on the inner cylinder and on the outer cylinder.
Solution Summary: The author explains the expression for tangential velocity profile, which is given as underset_u=rw.
A very small circular cylinder of radius Rtis rotating angular velocity
ω
i
, inside a much larger concentric cylinder of radius R0that is rotating at angular velocity
ω
0
. A liquid of density
ρ
and viscosity
μ
is confined between the two cylinders, as in Fig. P4-41. Gravitational and end effects can be neglected (the flow is two-dimensional into the page). If
ω
j
=
ω
0
and a long time has passed. generate an expression for the tangential velocity profile.
u
θ
as a function of (at most)
r
,
ω
,
R
j
,
R
o
,
ρ
. and
μ
. where
ω
=
ω
1
=
ω
0
. Also, calculate the torque exerted by the fluid on the inner cylinder and on the outer cylinder.
A cube of side (a) and mass (M) is initially sitting fully submerged at the bottom of a container filled
with a liquid of kinematic viscosity v and density p. The container has a square cross-section of side (a+a/5) and the cube is sitting right at the middle of the container base. (a) A force (F) starts pulling the cube up at a constant velocity (U). Develop an expression for the
force in terms of (U, M. a. g, p and v). You may assume that the velocity in the gap between the cube's sides and the container walls is linear. The expression for (F) is to be valid as long as the cube remains submerged.
(b) After the cube reaches the water surface, it continues to be pulled up by the same force. Develop a differential equation for the variation with time of the fraction of the cube that is submerged in water.
A film of liquid with kinematic viscosity and density p spreads over a flat
horizontal surface due to gravity as shown. Assume that the spread is planar in x - y plane
with unit width into page. The height of the film is h(x, t) which varies in a direction and
time t. The flow is incompressible and the x-velocity is u(x, y, t) which is governed by the
lubrication theory due to the small thickness of the film (h < L). The pressure outside
the film is uniform and atmospheric. Inside the film the pressure variation is hydrostatic
in y direction. At x = 0, h = h, and h is symmetric in z (i.e., h(L,t) = h(-L, t)). The
gravitational acceleration is g.
x=-L
hexat) ấy
x
u(x, y, t) = -2y(2h - y).
x=L
Show that +(udy) = 0
Using lubrication theory show that the velocity profile
↓g
Assuming that Oh/dt = constant, use (a) and (b) results to find h(r, t) in term
of ho, x, ah/ot, v, L and g.
1. For the shown conic body which rotating with constant angular
velocity 10 rad/s, find the torque which effected by viscosity of the oil that
surrounding the conic body.
Take:
Radius of the cone is 2 in Height of the cone is 4 in
Oil viscosity is 3.125x107 lb.s/in?
Answer : Torque =0.02535 lb. In
P10 rad/s
0.01-in film
0.01 in
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