Experiment Instructions: HM 225.03 Bernoulli's Principle

Experiment Instructions
HM 225.03 Bernoulli’s Principle

HM 225.03 BERNOULLI’S PRINCIPLE
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 11/2015
Experiment Instructions
Dipl.-Geogr. Uta Linke
This manual must be kept by the unit.
Before operating the unit:

- Read this manual.
- All participants must be instructed on
handling of the unit and, where appropriate,
on the necessary safety precautions.
Version 1.0 Subject to technical alterations
i
Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.1 Intended use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.2 Structure of safety instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.3 Safety instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.4 Ambient conditions for the operating and storage location . . . . . . . . . 3
3 Description of the device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3.1 Device design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.3 Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.3.1 Moving the pilot-static tube . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.3.2 Converting the Venturi side body . . . . . . . . . . . . . . . . . . . . . . 8
4 Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5 Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.1 Objective of the experiment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.2 Conducting the experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.3 Measured values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.4 Analysis of the experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.1 Technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.2 List of abbreviations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
6.3 List of formula symbols and units . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
6.4 Conversion tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
6.5 Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
ii
1 Introduction
The accessory unit HM 225.03 Bernoulli's Prin-

ciple is used in combination with the HM 225 Aer-
odynamics Trainer to study Bernoulli's principle
experimentally.
Learning objectives are

• investigation of the continuity equation and
Bernoulli's principle
• determination of the dynamic pressure from the

measurement data via Bernoulli's principle
• calculation of the flow velocity from themeas-
urement data using Bernoulli's equation
• pressure and velocity distribution
1 Introduction 1
2 Safety
2.1 Intended use
The unit is to be used only for teaching purposes.
2.2 Structure of safety instructions
The signal words DANGER, WARNING or

CAUTION indicate the probability and potential
severity of injury.
An additional symbol indicates the nature of the

hazard or a required action.
Signal word Explanation
Indicates a situation which, if not avoided, will result in

DANGER death or serious injury.
Indicates a situation which, if not avoided, may result in

WARNING death or serious injury.
Indicates a situation which, if not avoided, may result in

CAUTION minor or moderately serious injury.
Indicates a situation which may result in damage to

NOTICE equipment, or provides instructions on operation of
the equipment.
2 Safety 2
Symbol Explanation
Hazard area (general)
Note
2.3 Safety instructions

WARNING
Sharp-edged and sensitive pilot-static tube.
The tip of the pilot-static tube may cause injury, for
example to the eyes.
The pilot-static tube is very sensitive. It can easily
be bent or damaged.
• Handle the pilot-static tube with care.
WARNING
Risk of injuries
• Please also note the safety information in the
instructions for the HM 225 Aerodynamics
Trainer.
2.4 Ambient conditions for the operating and storage location
• Enclosed space.
• Free from dirt and humidity.
• Level and fixed surface.
• Frost-free.
2 Safety 3
3 Description of the device
3.1 Device design
6
3
7
1 Measuring hose 5 Pilot-static tube

2 Base cabinet 6 Front disk with scale
3 Knurled screw 7 Venturi side bodies
4 Clamp fastener seat 8 Locking screw
Fig. 3.1 Design of the HM 225.03 device
3 Description of the device 4

The accessory unit HM 225.03 Bernoulli's Prin-

ciple is intended for installation in the HM 225
Aerodynamics Trainer. It is inserted into the
measuring section of the trainer with clamp fas-
teners.
The base box includes two side bodies that sim-
ulate a Venturi nozzle.
A pilot-static tube runs along the centre of the

Measurement port two Venturi side bodies. The pilot-static tube can
for total pressure
be moved along the measuring section. A scale
indicates its position.

The pilot-static tube has two measuring points:
Measurement port • A measurement port in the direction of flow is

for static pressure used to measure the total pressure.
• Eight measurement ports are located in a circle
along the sides of the sensor. They are located
vertically to the direction of flow and form a
measuring point over the annular space for
measuring the static pressure.
The pilot-static tube is connected to two manom-
eter hoses of the HM 225 trainer with measuring
hoses.
The knurled screws are used to screw the two
Venturi side bodies to the base box. You may
also install your own models here to measure the
Fig. 3.2 Section through the pilot-static pressure distribution with the pilot-static tube.
tube

3.2 Installation
Stabilisation
tank (HM 225)
Nozzle (HM 225)

HM 225.03
Fig. 3.3 Installation
1. Clip the nozzle into the clamp bracket on the

HM 225 stabilisation tank.
2. Clip the accessory unit HM 225.03 into the
clamp bracket of the nozzle.
If necessary, adjust the nuts to shorten or
extend the clamps (see Fig. 3.4).
Nut Clamp
Fig. 3.4 Clamp bracket

3. Connect the two measuring points with two

manometer hoses of the HM 225 trainer,
see Fig. 3.3. Use the supplied measuring
hoses to do so.
• Connect the vertical measuring gauge
with manometer hose 1 (to measure the
total pressure).
• Connect the horizontal measuring gauge
with manometer hose 2 (to measure the
static pressure).
Measuring Measuring gauge

gauge for for static pressure
total pressure
1 2
Fig. 3.5 Structure

3.3 Operation
3.3.1 Moving the pilot-static tube
Loosen the locking screw and move the pilot-

static tube along the measuring section.
NOTICE
There is an offset between the measurement port
for total pressure and the measurement ports for
static pressure.
• For both pressures to be measured in the same

position the pilot-static tube must be moved
Fig. 3.6 Measurement position 15 mm between measurements.
3.3.2 Converting the Venturi side body
The contraction between the two side bodies is

• between 60 mm and 100 mm
• or between 200mm and 240mm.
NOTICE
Each side body weighs approx. 900 g. If the side
bodies fall down they may cause damage to the
device.
For each side body:

1. Hold the side body.
Contraction Contraction
between 60 mm between 200mm 2. Loosen the knurled screw on the side body
and 100 mm and 240mm and carefully pull the side body down and
Fig. 3.7 Venturi side bodies out of the base box.

4 Fundamentals
The basic principles set out in the following make

no claim to completeness. For further theoretical
explanations, refer to the specialist literature.
The continuity equation states that the volumet-

ric flow rate in a pipe is constant. The cross-sec-
tion area and the flow velocity are inversely pro-
v2 portional to each other.
v1
A2 ·
A1 · · V = A  v = constant (4.1)
V1 = V2
·
V Volume flow
Fig. 4.1 Flow through pipe sections
with different cross-section A Cross-section area
areas
v flow velocity
The continuity equation applies to incompressible
fluids, i.e. fluids the density of which does not
depend on the pressure. The density of com-
pressible fluids (gases) is pressure-dependent.
Gases with slight pressure differences are not
regarded as incompressible. The continuity equa-
tion also applies here.
For Fig. 4.1 we can therefore state that there is a
lower flow velocity in the left pipe section with the
larger cross-section area while the flow velocity is
higher in the right pipe section with the smaller
cross-section area. The volumetric flow rate is the
same in both pipe sections.
· ·
V1 = V2 = A1  v1 = A2  v2 (4.2)
4 Fundamentals 9
The Bernoulli principle states that the sum of the

static pressure, dynamic pressure and geodetic
pressure is constant. This requires a constant
mass flow rate and a frictionless flow.
 2
p total =  p stat  +  ---  v  +    g  h  = constant (4.3)
2 
ptotal total pressure

pstat static pressure
 density of the fluid
v flow velocity
g gravitational acceleration
h height
The following applies
 p stat  static pressure. This is the
pressure that the air at rest
exerts on an area.
 ---  v 2 dynamic pressure. The
2 
dynamic pressure is generated
by the flowing air and depends
on the velocity of the air.
  g  h Geodetic pressure depending

on height.
If the height remains the same, the geodetic pres-
sure does not apply. In this case, the following
principle applies:
 2
p total =  p stat  +  ---  v  = constant (4.4)
2 
or
p total = p stat + p dyn = constant (4.5)
4 Fundamentals 10
The example in Fig. 4.1 exhibits a higher static

pressure and a lower dynamic pressure in the left
pipe section (larger cross-section area). In the
right pipe section (smaller cross-section area), on
the other hand, the static pressure is lower and
the dynamic pressure is higher. The total pres-
sure is the same in both pipe sections.
We can conclude: The higher the flow velocity of
a fluid the lower the static pressure.
The pilot-static tube and the manometer hoses

are used to measure water columns.
pstat
ptotal
pdyn
h1 h2 href
Fig. 4.2 Pressures at the pilot-static tube
4 Fundamentals 11
The individual pressures are calculated as fol-

lows:
p total = h ref – h 1 (4.6)
p stat = h ref – h 2 (4.7)
p dyn = p total – p stat (4.8)
href reference water column

h1 water column in manometer hose 1
h2 water column in manometer hose 2

pdyn dynamic pressure
pstat static pressure
ptotal total pressure
The flow velocity v is then calculated from the

dynamic pressure:
2  p dyn
v = ------------------
- (4.9)

v flow velocity
pdyn dynamic pressure
 density of the fluid
4 Fundamentals 12
5 Experiments
The selection of experiments makes no claims of

completeness but is intended to be used as a
stimulus for your own experiments.
The results shown are intended as a guide only.
Depending on the construction of the individual
components, experimental skills and environmen-
tal conditions, deviations may occur in the experi-
ments. Nevertheless, the laws can be clearly
demonstrated.
5.1 Objective of the experiment
In this experiment we will record the total pressure

and the static pressure along the measuring sec-
tion. Based on these values we will calculate the
dynamic pressure and the flow velocity and eval-
uate the results with reference to the cross-sec-
tion area.
5.2 Conducting the experiment
1. Install the accessory unit HM 225.03 on the

HM 225 trainer, see Chapter 3.2, Page 6.
Fig. 5.1 Experiment set-up
5 Experiments 13
2. On the HM 225 trainer:

• Open valve V1 fully.
• Close valve V2 fully.
• Set a medium flow velocity (potentiome-
ter 4...6).
• Switch on the fan.
WARNING
Risk of injuries
• Please also note the safety information in the

instructions for the HM 225 Aerodynamics
Trainer.
3. Measure the pressures and record them on

your worksheet (see Chapter 6.5, Page 24).
• Move the pilot-static tube until the tip is in
the 5mm position. Read the measured
value h1 from manometer hose 1.
• Move the pilot-static tube until the meas-
urement ports on the side are in the 5mm
position. Read the measured value h2
from manometer hose 2.
• Read the measured value href from
manometer hose 3.
4. In steps of 5 mm, move the pilot-static tube
along the measuring section and repeat the
measurements. The measuring series ends
at 295 mm.
5 Experiments 14
5.3 Measured values
Tab. 5.1 contains sample measured values. The

individual pressures and flow velocities were cal-
culated using Formula (4.6), Page 12, to
Formula (4.9), Page 12. The cross-section areas
in each measuring position were taken from
Chapter 6.1, Page 20.
Position A h1 h2 href ptotal Pstat pdyn v

in mm in mm² in mm in mm in mm in mm in mm in mm in m/s
WC WC WC WC WC WC
5 3415,0 160 186 201 41 15 26 20,8
10 3250,0 160 187 201 41 14 27 21,2
15 3125,0 160 190 201 41 11 30 22,4
20 3000,0 160 193 201 41 8 33 23,5
25 2875,0 160 196 201 41 5 36 24,5
30 2750,0 160 200 201 41 1 40 25,8
35 2625,0 160 204 201 41 -3 44 27,1
40 2500,0 160 209 201 41 -8 49 28,6
45 2375,0 160 214 201 41 -13 54 30,0
50 2250,0 160 220 201 41 -19 60 31,6
55 2125,0 160 225 201 41 -24 65 32,9
60 2000,0 160 230 201 41 -29 70 34,2
65 2000,0 160 235 201 41 -34 75 35,4
70 2000,0 160 237 201 41 -36 77 35,8
75 2000,0 160 239 201 41 -38 79 36,3
80 2000,0 160 239 201 41 -38 79 36,3
85 2000,0 160 240 201 41 -39 80 36,5
90 2000,0 160 240 201 41 -39 80 36,5
95 2000,0 160 240 201 41 -39 80 36,5
100 2000,0 160 240 201 41 -39 80 36,5
105 2037,5 160 239 201 41 -38 79 36,3
110 2075,0 160 237 201 41 -36 77 35,8
115 2112,5 160 236 201 41 -35 76 35,6
120 2150,0 160 234 201 41 -33 74 35,1
125 2187,5 160 232 201 41 -31 72 34,6
Tab. 5.1 Measured values
5 Experiments 15
Position A h1 h2 href ptotal Pstat pdyn v

in mm in mm² in mm in mm in mm in mm in mm in mm in m/s
WC WC WC WC WC WC
130 2225,0 160 230 201 41 -29 70 34,2
135 2262,5 160 229 201 41 -28 69 33,9
140 2300,0 160 227 201 41 -26 67 33,4
145 2337,5 160 225 201 41 -24 65 32,9
150 2375,0 160 224 201 41 -23 64 32,7
155 2412,5 160 222 201 41 -21 62 32,1
160 2450,0 160 221 201 41 -20 61 31,9
165 2487,5 160 220 201 41 -19 60 31,6
170 2525,0 160 218 201 41 -17 58 31,1
175 2562,5 160 217 201 41 -16 57 30,8

180 2600,0 160 215 201 41 -14 55 30,3
185 2637,5 160 214 201 41 -13 54 30,0
190 2675,0 160 213 201 41 -12 53 29,7
195 2712,5 160 212 201 41 -11 52 29,4
200 2750,0 160 211 201 41 -10 51 29,2
205 2787,5 160 210 201 41 -9 50 28,9
210 2825,0 160 209 201 41 -8 49 28,6
215 2862,5 160 209 201 41 -8 49 28,6
220 2900,0 160 208 201 41 -7 48 28,3
225 2937,5 160 207 201 41 -6 47 28,0
230 2975,0 160 206 201 41 -5 46 27,7
235 3012,5 160 205 201 41 -4 45 27,4
240 3050,0 160 205 201 41 -4 45 27,4
245 3087,5 160 204 201 41 -3 44 27,1
250 3125,0 160 203 201 41 -2 43 26,8
255 3162,5 160 202 201 41 -1 42 26,5
260 3200,0 160 202 201 41 -1 42 26,5
265 3237,5 160 201 201 41 0 41 26,1
270 3275,0 160 200 201 41 1 40 25,8
275 3312,5 160 199 201 41 2 39 25,5
280 3350,0 160 198 201 41 3 38 25,2
285 3387,5 160 196 201 41 5 36 24,5
290 3425,0 160 193 201 41 8 33 23,5
295 3562,0 160 189 201 41 12 29 22,0
Tab. 5.1 Measured values
5 Experiments 16
5.4 Analysis of the experiment
The values for total pressure, static pressure and

dynamic pressure as well as the cross-section
areas of the Venturi nozzle are indicated in Fig.
5.2.
Pressure in mm WC Cross-section area in mm²

-60 -40 -20 0 20 40 60 80 100 0 1000 2000 3000 4000 5000
0 0
20 20
40 40
60 60
80 80
100 100
120 120
140 140
160 160
180 180
200 200
Position in mm
Position in mm
220 220
240 240
260 260
280 280
300 300
Total pressure ptotal Cross-section area in mm²
Static pressure pstat
Dynamic pressure pdyn
Fig. 5.2 Pressure distribution and cross-section areas in the Venturi nozzle
The total pressure is 41 mm WC in all measuring

positions. This confirms Bernoulli's principle,
which states that the total pressure is constant in
all measuring positions.
5 Experiments 17
At the start of the Venturi nozzle the static pres-

sure is 15mm WC (measuring position 5mm with
a cross-section area of 3415,0mm²). The cross-
section area decreases continuously until it
reaches the contraction. At the same time, the
static pressure drops to -39 mm WC (measuring
position 85mm to 100mm, 2000,0mm² cross-sec-
tion area each). Behind the contraction the static
pressure rises to 12 mm WC (measuring position
295mm with cross-section area 3562,0mm²).
We can see that the static pressure drops when
the cross-section area decreases and rises when

the cross-section area increases. From measur-
ing position 35 mm to 260 mm there is a negative
static pressure, i.e. a negative pressure, in the
Venturi nozzle.
The dynamic pressure is 26mm WC at the
beginning of the Venturi nozzle (measuring posi-
tion 5mm with a cross-section area of
3415,0mm²). It rises continuously to a maximum
of 80 mm WC in the contraction (measuring posi-
tion 85mm to 100mm, 2000,0mm² cross-section
area each). Behind the contraction the dynamic
pressure drops to 29mm WC (measuring position
295mm with cross-section area 3562,0mm²).
The dynamic pressure rises when the cross-sec-
tion area decreases and drops when the cross-
section area increases. It behaves inversely pro-
portional to the static pressure.
Fig. 5.3 indicates the values for the flow velocities

and cross-section areas in the Venturi nozzle.
5 Experiments 18
Flow velocity in m/s Cross-section area in mm²

0 5 10 15 20 25 30 35 40 45 50 0 1000 2000 3000 4000 5000
0 0
20 20
40 40
60 60
80 80
100 100
120 120
140 140
160 160
180 180
200 200
Position in mm
Position in mm
220 220
240 240
260 260
280 280
300 300
Flow velocity v Cross-section area in mm²
Fig. 5.3 Flow velocities and cross-section areas in the Venturi nozzle
The flow velocity is 20,8m/s at the beginning of

the Venturi nozzle (measuring position 5mm with
a cross-section area of 3415,0mm²). The flow
velocity then rises to a maximum of 36,5m/s in the
contraction (measuring position 85mm to
100mm, 2000,0mm² cross-section area each).
Behind the contraction the flow velocity drops to
22,0m/s (measuring position 295mm with cross-
section area 3562,0mm²).
Thus the flow velocity, similar to the dynamic
pressure, rises when the cross-section area
decreases and drops when the cross-section area
increases.
5 Experiments 19
6 Appendix
6.1 Technical data
Dimensions
Length x Width x Height 230 x 130 x 410 mm
Weight approx. 4 kg
Pilot-static tube
Diameter of the measurement ports for static pressure 0,4 mm
Diameter of the measurement port for total pressure 1,2 mm
Measuring section along the Venturi nozzle 5...295 mm
Venturi side bodies
Depth of the Venturi side bodies: 50 mm
6 Appendix 20
Position Nozzle outlet Position Nozzle outlet
Width Depth Cross- Width Depth Cross-

sectional sectional
area area
mm mm mm mm² mm mm mm mm²
5 68,30 50,00 3415,00 155 48,25 50,00 2412,50

10 65,00 50,00 3250,00 160 49,00 50,00 2450,00
15 62,50 50,00 3125,00 165 49,75 50,00 2487,50
20 60,00 50,00 3000,00 170 50,50 50,00 2525,00
25 57,50 50,00 2875,00 175 51,25 50,00 2562,50
30 55,00 50,00 2750,00 180 52,00 50,00 2600,00

35 52,50 50,00 2625,00 185 52,75 50,00 2637,50
40 50,00 50,00 2500,00 190 53,50 50,00 2675,00
45 47,50 50,00 2375,00 195 54,25 50,00 2712,50
50 45,00 50,00 2250,00 200 55,00 50,00 2750,00
55 42,50 50,00 2125,00 205 55,75 50,00 2787,50
60 40,00 50,00 2000,00 210 56,50 50,00 2825,00
65 40,00 50,00 2000,00 215 57,25 50,00 2862,50
70 40,00 50,00 2000,00 220 58,00 50,00 2900,00
75 40,00 50,00 2000,00 225 58,75 50,00 2937,50
80 40,00 50,00 2000,00 230 59,50 50,00 2975,00
85 40,00 50,00 2000,00 235 60,25 50,00 3012,50
90 40,00 50,00 2000,00 240 61,00 50,00 3050,00
95 40,00 50,00 2000,00 245 61,75 50,00 3087,50
100 40,00 50,00 2000,00 250 62,50 50,00 3125,00
105 40,75 50,00 2037,50 255 63,25 50,00 3162,50
110 41,50 50,00 2075,00 260 64,00 50,00 3200,00
115 42,25 50,00 2112,50 265 64,75 50,00 3237,50
120 43,00 50,00 2150,00 270 65,50 50,00 3275,00
125 43,75 50,00 2187,50 275 66,25 50,00 3312,50
130 44,50 50,00 2225,00 280 67,00 50,00 3350,00
135 45,25 50,00 2262,50 285 67,75 50,00 3387,50
140 46,00 50,00 2300,00 290 68,50 50,00 3425,00
145 46,75 50,00 2337,50 295 71,24 50,00 3562,00
150 47,50 50,00 2375,00
6 Appendix 21
6.2 List of abbreviations
Abbreviation Meaning
WC Water column
6.3 List of formula symbols and units
Formula sym-
Mathematical/physical variable Unit
bols
A Cross-section area: mm²
g Gravitational acceleration 9,81m/s²
h Water column
href Reference water column

mm WC
h1 Water column in manometer hose 1
h2 Water column in manometer hose 2
p Pressure
pdyn Dynamic pressure

mm WC
pstat Static pressure
ptotal Total pressure
v Flow velocity m/s

·
V Volume flow m³/h
 Density kg/m³
6 Appendix 22
6.4 Conversion tables
Unit mm3 cm3 L m3
1mm3 1 0,001 0,000001 0,000000001
1cm3 1.000 1 0,001 0,000001
1L 1.000.000 1.000 1 0,001
1m3 1.000.000.000 1.000.000 1.000 1
Tab. 6.1 Conversion table for units of volume

Unit L/s L/min L/h m3/min m3/h
1L/s 1 60 3.600 0,06 3,6
1L/min 0,01667 1 60 0,001 0,06
1L/h 0,000278 0,01667 1 0,00001667 0,001
1m3/min 16,667 1000 0,0006 1 60
1m3/h 0,278 16,667 1000 0,01667 1
Tab. 6.2 Conversion table for units of volume flow
Unit bar mbar Pa hPa kPa mm WC*
1bar 1 1.000 100.000 1.000 100 10.000
1mbar 0,001 1 100 1 0,1 10
1Pa 0,00001 0,01 1 0,01 0,001 0,1
1hPa 0,001 1 100 1 0,1 10
1kPa 0,01 10 1.000 10 1 100
1 mm WC * 0,0001 0,1 10 0,1 0,01 1
Tab. 6.3 Conversion table for units of pressure

* rounded figures
6 Appendix 23
6.5 Worksheet
Experiment no.
60 to 100
Position of the contraction of the Venturi nozzle
200 to 240
Water column at rest (before starting the experiment) mm
Air temperature °C
Potentiometer setting
Water column in mm WC
Position
in mm
h1 h2 href
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
6 Appendix 24
Experiment no.
Position
in mm
h1 h2 href
90
95
100
105
110
115
120
125
130
135
140
145
150
155
160
165
170
175
180
185
190
195
6 Appendix 25
Experiment no.
Position
in mm
h1 h2 href
200
205
210
215
220
225
230
235
240
245
250
255
260
265
270
275
280
285
290
295
6 Appendix 26

Experiment Instructions: HM 225.03 Bernoulli's Principle

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Experiment Instructions: HM 225.03 Bernoulli's Principle

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Experiment Instructions: HM 225.03 Bernoulli's Principle

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Experiment Instructions

HM 225.03 Bernoulli’s Principle

This manual must be kept by the unit.

Before operating the unit:

Version 1.0 Subject to technical alterations

3 Description of the device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

The accessory unit HM 225.03 Bernoulli's Prin-

Learning objectives are

• determination of the dynamic pressure from the

2.1 Intended use

The unit is to be used only for teaching purposes.

2.2 Structure of safety instructions

The signal words DANGER, WARNING or

An additional symbol indicates the nature of the

Signal word Explanation

Indicates a situation which, if not avoided, will result in

Indicates a situation which, if not avoided, may result in

Indicates a situation which, if not avoided, may result in

Indicates a situation which may result in damage to

Hazard area (general)

2.3 Safety instructions

2.4 Ambient conditions for the operating and storage location

3 Description of the device

3.1 Device design

1 Measuring hose 5 Pilot-static tube

Fig. 3.1 Design of the HM 225.03 device

3 Description of the device 4

The accessory unit HM 225.03 Bernoulli's Prin-

A pilot-static tube runs along the centre of the

indicates its position.

Measurement port • A measurement port in the direction of flow is

3 Description of the device 5

Nozzle (HM 225)

Fig. 3.3 Installation

1. Clip the nozzle into the clamp bracket on the

3 Description of the device 6

3. Connect the two measuring points with two

Measuring Measuring gauge

Fig. 3.5 Structure

3 Description of the device 7

3.3.1 Moving the pilot-static tube

Loosen the locking screw and move the pilot-

• For both pressures to be measured in the same

3.3.2 Converting the Venturi side body

The contraction between the two side bodies is

For each side body:

3 Description of the device 8

The basic principles set out in the following make

The continuity equation states that the volumet-

The Bernoulli principle states that the sum of the

ptotal total pressure

  g  h Geodetic pressure depending

The example in Fig. 4.1 exhibits a higher static

The pilot-static tube and the manometer hoses

Fig. 4.2 Pressures at the pilot-static tube

The individual pressures are calculated as fol-

p total = h ref – h 1 (4.6)

p stat = h ref – h 2 (4.7)

p dyn = p total – p stat (4.8)