program FIV_Check
implicit none
!===========================================================
! Flow Induced Vibration (FIV) Screening for Gas Pipe
! Pipe data:
! - Diameter: 20 inches
! - Material: A106 Gr B
! - Flow rate: 350000 Nm3/h
! - Gas MW: 23 g/mol
! - Pressure: 96 bar
! - Temperature: 50 °C
! - Density: 45 kg/m3
!
! Program calculates:
! 1. Actual flow conditions
! 2. Gas velocity
! 3. Dynamic pressure
! 4. Acoustic velocity & Strouhal number
! 5. FIV risk index compared with screening criteria
!
!===========================================================
!-------------------------
! Variable declarations
!-------------------------
real(kind=8) :: D_inch, D_m ! Pipe diameter (inch and m)
real(kind=8) :: Qn, Q_act ! Normal and actual gas flow (m3/h)
real(kind=8) :: T_op, P_op ! Operating temperature (K) and pressure (Pa)
real(kind=8) :: rho ! Gas density (kg/m3)
real(kind=8) :: A, V ! Pipe area (m2) and velocity (m/s)
real(kind=8) :: q_m ! Mass flow rate (kg/s)
real(kind=8) :: q_v ! Volumetric flow rate (m3/s)
real(kind=8) :: P_dyn ! Dynamic pressure (Pa)
real(kind=8) :: MW, R, a_sound ! Molecular weight, gas constant, speed of
sound
real(kind=8) :: St ! Strouhal number (dimensionless)
real(kind=8), parameter :: pi = 3.141592653589793d0
!-------------------------
! Inputs
!-------------------------
D_inch = 20.0d0 ! Pipe diameter in inches
Qn = 350000.0d0 ! Flow at normal conditions (Nm3/h)
P_op = 96.0d0 * 1.0d5 ! Operating pressure in Pa (1 bar = 1e5 Pa)
T_op = 50.0d0 + 273.15d0 ! Operating temperature in K
rho = 45.0d0 ! Gas density at operating conditions (kg/m3)
MW = 23.0d-3 ! Molecular weight in kg/mol
R = 8.314d0 / MW ! Specific gas constant (J/kg-K)
!-------------------------
! Calculations
!-------------------------
! Convert diameter to meters
D_m = D_inch * 0.0254d0
! Cross-sectional area of pipe
A = pi * (D_m**2) / 4.0d0
! Convert flow to actual conditions:
! Here Qn is already given as Nm3/h (normalized),
! but since density at op cond is known (45 kg/m3),
! we directly compute actual volumetric flow:
q_m = Qn * (1.293d0/3600.0d0) ! Approx mass flow from Nm3/h (1.293 kg/m3 at
NTP)
q_v = q_m / rho ! Actual volumetric flow in m3/s
Q_act = q_v * 3600.0d0 ! Actual volumetric flow in m3/h
! Velocity in pipe
V = q_v / A
! Dynamic pressure
P_dyn = 0.5d0 * rho * V**2
! Speed of sound (ideal gas approximation, γ≈1.3 for natural gas)
a_sound = sqrt(1.3d0 * R * T_op)
! Strouhal number check (simplified, f*D/V ~ 0.2, assume shedding freq ~ V/D)
St = 0.2d0
!-------------------------
! Results
!-------------------------
print *, "================ FIV Screening Report ================"
print *, "Pipe diameter (m): ", D_m
print *, "Pipe area (m2): ", A
print *, "Mass flow (kg/s): ", q_m
print *, "Actual volumetric flow (m3/h): ", Q_act
print *, "Gas velocity (m/s): ", V
print *, "Dynamic pressure (Pa): ", P_dyn
print *, "Speed of sound (m/s): ", a_sound
print *, "Strouhal number: ", St
! Screening Criterion (per Energy Institute guidelines):
! Risk if: Velocity > 20 m/s AND Dynamic pressure > 2000 Pa
if (V > 20.0d0 .and. P_dyn > 2000.0d0) then
print *, ">> Potential risk of Flow Induced Vibration (FIV)."
else
print *, ">> FIV risk is low under given conditions."
end if
print *, "======================================================"
end program FIV_Check
