Calculate velocity using a pitot tube free#

Water Flow - Velocity and Dynamic Head Chart Due to low dynamic pressure (head) the readings will be inaccurate. Note that as indicated in the diagram above - pitot tubes are not suited for low velocity flow. Air Flow - Velocity and Dynamic Head Chart (pdf).The charts below are based on air density 1.205 kg/m 3 and water density 1000 kg/m 3. The head - Δh - (or pressure difference - Δp) can be measured and calculated with the help of u-tube manometers, electronic pressure transmitters or similar instrumentation.Īir Flow - Velocity and Dynamic Head Chart The pitot tube is a simple and convenient instrument to measure the difference between static, total and dynamic pressure (or head). For other units and reference liquids - like mm Water Column - check Velocity Pressure Head. Note! - in the basic equation the head unit is with reference to the density of the flowing fluid. Δh = h 2 - h 1 = height difference (fluid column) (4) can be modified by dividing with specific weight γ toĬ = coefficient - depending on reference liquid and units used or calculated It is common to use head instead of pressure.

Calculate velocity using a pitot tube free#

With (4) it's possible to calculate the flow velocity in point 1 - the free flow upstream - if we know the differential pressure difference Δp = p 2 - p 1 and the density of the fluid.

Since v 2 is zero, (2) can be modified to: In a measuring point we regard the hydrostatic pressure as a constant where h 1 = h 2 - and this part can be eliminated. Suffix 2 is the stagnation point where the velocity in the flow is zero Flow Velocity Suffix 1 is a point in the free flow upstream

The Bernoulli Equation states that the energy along a streamline is constant - and can be modified to It represent the pressure due to change in elevation. The third term - γ h - is called the hydrostatic pressure. The second term - 1/2ρ v 2 - is called the dynamic pressure. It is static relative to the moving fluid and can be measured through a flat opening in parallel to the flow. The first term - p - is the static pressure. P = static pressure (relative to the moving fluid) (Pa)Įach term of the equation has the dimension force per unit area N/m 2 (Pa) - or in imperial units lb/ft 2 (psi). The principle is based on the Bernoulli Equation where each term of the equation can be interpreted as pressure A pitot tube can be used to measure fluid flow velocity by converting the kinetic energy in a fluid flow to potential energy.