Pipe bend segment in an isothermal liquid network
Simscape / Fluids / Isothermal Liquid / Pipes & Fittings
The Pipe Bend (IL) block models a curved pipe in an isothermal liquid network. You can define the pipe characteristics to calculate losses due to friction and pipe curvature and optionally model fluid compressibility.
The coefficient for pressure losses due to geometry changes comprises an angle correction factor, Cangle, and a bend coefficient, Cbend:
Cangle is calculated as:
where θ is the Bend angle, in degrees.
Cbend is calculated from the tabulated ratio of bend radius to pipe diameter for 90o bends from Crane :
The friction factor, fT, for clean commercial steel is interpolated from tabular data based on pipe diameter :
Note that the correction factor is valid for a ratio of bend radius to diameter between 1 and 24. Beyond this range, nearest-neighbor extrapolation is employed.
The pressure loss formulations are the same for the flow at ports A and B.
When the flow in the pipe is fully laminar, or below Re = 2000, the pressure loss over the bend is:
μ is the fluid dynamic viscosity.
λ is the Darcy friction factor constant, which is 64 for laminar flow.
ρI is the internal fluid density.
d is the pipe diameter.
L is the bend length segment, the product of the Bend radius and the Bend angle: .
A is the pipe cross-sectional area,
is the mass flow rate at the respective port.
When the flow is fully turbulent, or greater than Re = 4000, the pressure loss in the pipe is:
where fD is the Darcy friction factor. This is approximated by the empirical Haaland equation and is based on the Internal surface absolute roughness. The differential is taken over half of the pipe segment, between port A to an internal node, and between the internal node and port B.
When the flow is incompressible, the pressure loss over the bend is:
When the flow is compressible, the pressure loss over the bend is calculated based on the internal fluid volume pressure, pI:
For an incompressible fluid, the mass flow into the pipe equals the mass flow out of the pipe:
When the fluid is compressible, the difference between the mass flow into and out of the pipe depends on the fluid density change due to compressibility:
where V is the product of the pipe cross-sectional area and bend length, AL.
A— Liquid port
Liquid entry or exit port.
B— Liquid port
Liquid entry or exit port.
Pipe diameter— Pipe diameter
0.01 m(default) | positive scalar
Diameter of the pipe.
Bend radius— Bend circle radius
0.04 m(default) | positive scalar
Radius of the circle formed by the pipe bend.
Bend angle— Bend angle
90 deg(default) | positive scalar
Swept degree of the pipe bend.
Internal surface absolute roughness— Pipe wall roughness
15e-6 m(default) | positive scalar
Pipe wall absolute roughness. This parameter is used to determine the Darcy friction factor, which contributes to pressure loss in the pipe.
Fluid dynamic compressibility— Whether to model fluid compressibility
Whether to model any change in fluid mass due to fluid compressibility.
When Fluid compressibility is set to
On, mass changes due to varying fluid density
in the segment are calculated. The fluid volume in the pipe remains
constant. In the Isothermal Liquid library, all blocks calculate density as
a function of pressure.
Initial liquid pressure— Pipe pressure at beginning of simulation
0.101325 MPa(default) | positive scalar
Pipe pressure at the beginning of the simulation.
To enable this parameter, set Fluid dynamic
 Crane Co. Flow of Fluids Through Valves, Fittings, and Pipe TP-410. Crane Co., 1981.