2. • Measurement is made in such a way that the
velocity of the flow is not disturbed, then the
measured pressure indicates the static pressure
• If the flow is brought to rest isentropically, then
the pressure obtained, becomes the stagnation
pressure.
3. • While measuring pressures through probe,
the position of sensing holes and the support
stem is very important. The deviation of actual
and measured pressure may arise due to nose
effect and stem effect. Since, both the effects
have opposite nature; it may be possible to
cancel these effects by suitable design.
4. • Static Pressure Measurement
Small hole is drilled normal to the surface (pressure tapping) so that
pressure measuring device can be connected
Inner walls of duct flows
Outer Surface of an aerofoil
5. Static pressure at any interior point in the flow.
Inserted without disturbing the flow
streamlines.
Leading end of probe is closed & one or more
static holes drilled on its surface.
• Probe should be small
• Parallel to flow direction
• If Hole diameter is large
deflection will be
considerable
• Hole dia should be small(not
too less ,response time will
be long(.25-2.5mm) )
6. STAGNATION PRESSURE
• Pressure probe placed parallel to
flow with open end facing the
stream.
• Other end connected to a pressure
measuring devices like manometer
• Cannot able to use low Reynolds
number flows.(since deceleration
may not be isentropic)
• If flow is adiabatic due to frictional
effect or shock wave entropy
change occurs then(Stagnation
Pressure ≠ reservoir pressure)
