Orifice Flow
Calculate liquid discharge flow rate through an orifice using Q = Cd × A × √(2gH). Free online orifice flow calculator for fluid dynamics with charts and breakdown tables.
About This Calculator
The Orifice Flow Calculator estimates the volumetric flow rate of liquid discharged from a tank through an orifice opening. This tool is essential for engineers, students, and professionals working in fluid dynamics, hydraulics, and mechanical engineering applications such as water tank design, pipe systems, weirs, spillways, and hydraulic equipment.
The calculation uses the standard orifice flow equation: Q = Cd × A × √(2gH), where Q is the flow rate in m³/s, Cd is the coefficient of discharge, A is the cross-sectional area of the orifice (πd²/4), g is the gravitational acceleration (9.81 m/s²), and H is the centerline head — the vertical distance from the liquid surface to the center of the orifice.
The coefficient of discharge (Cd) accounts for energy losses, vena contracta effects, and flow contraction at the orifice. For sharp-edged circular orifices, Cd is typically around 0.62. Rounded or bell-mouth orifices have higher Cd values up to 0.98. The orifice meter is widely used in industrial flow measurement due to its simplicity, low cost, and reliability.
Regional Notes
India: Orifice meters are commonly used in water supply systems, irrigation projects, and industrial pipelines following IS 2959 standards for flow measurement.
US: The ASME MFC-7M standard governs orifice plate flow measurement. Pipe diameters and flow rates are often expressed in inches and US gallons per minute (gpm).
UK: BS EN ISO 5167 specifies orifice plate design and installation requirements. Flow measurement in water distribution networks commonly uses orifice meters for leak detection and network analysis.
Frequently Asked Questions
What is the orifice flow equation?
The orifice flow equation is Q = Cd × A × √(2gH), where Q is the volumetric flow rate, Cd is the coefficient of discharge, A is the cross-sectional area of the orifice, g is gravitational acceleration (9.81 m/s²), and H is the centerline head measured from the water surface to the center of the orifice.
What is a typical coefficient of discharge for an orifice?
For a sharp-edged orifice, the coefficient of discharge (Cd) typically ranges from 0.60 to 0.65, with 0.62 being a common value. For rounded or bell-mouth orifices, Cd can be as high as 0.98. The value depends on the orifice geometry, Reynolds number, and flow conditions.
How do you calculate the flow rate through an orifice?
To calculate orifice flow rate, first compute the orifice area A = πd²/4 using the diameter d. Then multiply by the coefficient of discharge Cd and the square root of 2gH (where g = 9.81 m/s² and H is the head). The formula is Q = Cd × A × √(2gH).
What units does the orifice flow calculator use?
The calculator uses millimeters (mm) for orifice diameter, meters (m) for centerline head, and the discharge result is shown in cubic meters per second (m³/s). The coefficient of discharge is a dimensionless value between 0 and 1.
What is the difference between an orifice meter and a venturi meter?
An orifice meter uses a flat plate with a hole to create a pressure drop, while a venturi meter uses a convergent-divergent section. Orifice meters have higher permanent pressure loss (40-90%) compared to venturi meters (10-20%), but are cheaper and easier to install.
Can this calculator be used for compressible fluids like gases?
This calculator is designed for incompressible fluids like water. For compressible fluids (gases), the orifice flow equation includes an expansion factor that accounts for density changes. Compressible flow calculations are more complex and require additional parameters.
What factors affect the coefficient of discharge?
The coefficient of discharge is affected by the orifice diameter, the Reynolds number of the flow, the sharpness of the orifice edge, the pipe diameter ratio (beta ratio), and the kinematic viscosity of the fluid. Higher Reynolds numbers generally lead to more stable Cd values.