Lectures 9-10 Flashcards
In a rough pipe, the shape of the velocity profile created by the turbulent fluid will be
more rounded and pointy
In a smooth pipe, the shape of the velocity profile created by the turbulent fluid will be
more flatter and less pointy
Laminar flow compared to turbulent flow has a velocity profile that is
more pointy down the neutral axis of the pipe
Laminar flow is not affected by the —– — — —— when creating a velocity profile for it
roughness of the pipe
Between 2000-4000 Reynold’s number, the flow is usually
transition flow
Under 2000 Reynold’s number, the flow is usually
laminar
Above 4000 Reynold’s number, the flow is usually
turbulent
Re =
Reynold’s number =
(ρ v D) / μ
( density of fluid X avg velocity X diameter ) / dynamic viscosity
The entrance flow is
the distance it takes for a fluid to enter a pipe and fully develop it’s velocity profile
Does the reynold’s number have a unit?
No
If static pressure decreases, —– —— increases
dynamic pressure
When the fluid is in the entrance flow, the drop in ——- ——– drives the fluid forward by converting the pressure to ——– ——-
static pressure, dynamic pressure
Friction force depends on three main characteristics:
- solid characteristics
- fluid characteristics
- relative velocity
Solid chracteristics include 2:
- geometry (size D)
-particle roughness
Fluid chracteristics include 1:
- density/viscosity
Relative velocity chracteristics include 1:
- velocity of solid vs fluid
After much research, the friction factor equation was observed by —— to be:
Moody
f = 4 (16 / Re)
In a laminar flow, the shear stress is directly proportional to ——- ——-
viscous drag
In a pipe with laminar flow, it is a —— —– relationship to the —— ——-
directly proportional, shear stress
Pressure drop in a pipeline is directly proportional to ….
aspect ratio of the pipe
Laminar flow theory states the relationship between the velocity and pipe radius is
V = Vmax ( 1 - r^2 / R^2)
Darcy Weisbach equation is
ΔPL = f (L/D) (1/2) ρ (Vavg)^2
Pressure loss = friction factor X (aspect ratio of pipe) X (1/2) X density of fluid X (avg velocity)^2
In a laminar flow, the friction factor is stated as
f = 64/Re
Conservation of energy equation of a system
E sys / dt = W (per unit time) net in + Q (per unit time) net in
CLOSED system momentum conservation equation
M1 v1i + M2 v2i = M1 v1f + M2 v2f
Body forces are those that
act throughout the body of a fluid control volume
Surface forces are those that
act on the control volume’s surface
3 types of forces on fluid inside of a control volume
1) External body forces
2) Fluid-fluid surface forces
3) Fluid-solid contact forces
Example of external body forces
- gravity
- magnetic
Example of fluid-fluid surface forces
- pressure
- viscous forces
Example of fluid-solid contact forces
Rate of change of linear momentum conservation for a control volume is
d (m V)CV / dt = Σ F (applied on CV surface) + Σ (m V)in - Σ (m V)out
How can this equation be split up into its individual components?
Σ F = m (V2 - V1) => ….
Σ Fx = m (V2x - V1x)
Σ Fy = m (V2y - V1y)
Σ Fz = m (V2z - V1z)
What happens to atmospheric forces acting on a closed fluid control volume?
They can be ignored as they cancel out
As the forces apply on all surfaces of the control volume
