Equipment for Engineering Education - Πολυτεχνική Σχολή 170/Hm170e.pdf ·  ·...

34
Equipment for Engineering Education Operating Instructions HM170 Educational Wind Tunnel G.U.N.T. Gerätebau GmbH P.O. Box 1125 D-22881 Barsbüttel Germany Phone (040) 670854-0 Fax (040) 670854-41

Transcript of Equipment for Engineering Education - Πολυτεχνική Σχολή 170/Hm170e.pdf ·  ·...

Equipment for Engineering Education

Operating Instructions

HM170 Educational Wind Tunnel

G.U.N.T. Gerätebau GmbHP.O. Box 1125D-22881 Barsbüttel • GermanyPhone (040) 670854-0Fax (040) 670854-41

Publication no.: 917.000 00A 170 12 11/94

Operating Instructions

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Table of contents

1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2 Technical description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.1 Function of the wind tunnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.2.1 Wind tunnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.2.2 Force measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4 Commissioning and operation . . . . . . . . . . . . . . . . . . . . . . . 10

4.1 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4.2 Commissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

4.2.1 Checking inclined-tube manometer . . . . . . . . . . . . . . . . . . 11

4.2.2 Removing the transport safety device. . . . . . . . . . . . . . . . . 11

4.2.3 Opening and closing measurement section . . . . . . . . . . . . 11

4.2.4 Operation of fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4.3 Speed measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4.3.1 Measurement with built-in instrument . . . . . . . . . . . . . . . . . 14

4.3.2 Measurement with Prandtl tube . . . . . . . . . . . . . . . . . . . . . 15

4.3.3 Calibration of speed measurement . . . . . . . . . . . . . . . . . . . 16

4.4 Installation of models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4.5 Force measurement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

4.5.1 Force transducer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

4.5.2 Measurement amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4.5.3 Error due to influence of dead weight . . . . . . . . . . . . . . . . . 21

4.5.4 Error caused by model holder. . . . . . . . . . . . . . . . . . . . . . . 22

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5 Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

6 Appendices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

6.1 Technical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

6.2 List of symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

6.3 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

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1 Introduction

The HM 170 demonstration wind tunnel wasdeveloped for experimentation and demonstrationpurposes in the fields of aerodynamics and fluidmechanics. It is a subsonic, open wind tunnel witha square measurement-section profile. The ex-tensive range of available accessories permitsthe performance of numerous experiments, e.g.:

- Comparison of various methods of velocity andpressure measurement

- Determination of drag coefficients of differentbodies (disc, sphere, streamlined object, aero-foil)

- Determination of drag and lift coefficients ofaerofoils at different angles of attack

- Effect of aerodynamic aids such as slots andflaps

- Pressure distribution with flow around cylindersand aerofoils

- Instability at an aerofoil, aerodynamic continu-ous excitation

- Examination of boundary layers

In addition to traditional flow measurementmethods, provision is made for computer-aideddata acquisition and evaluation using electronicpressure transducers and position sensors.Data can be transfered to a PC via a measurementamplifier with built-in AD converter and serialinterface. A special software package permitsthe generation of lift and pressure distributioncurves.

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1 Introduction 1

2 Technical description

A wind tunnel essentially consists of the following:

- Prechamber with flow straightener (1)

- Jet (2)

- Measurement section (3)

- Diffuser (4)

- Fan (5)

The HM170 demonstration wind tunnel is an openwind tunnel of the so-called Eiffel type, where theair is drawn in from outside and blown back out intothe open. The surrounding area returns the airto the inlet. This type of wind tunnel is onlysuitable for relatively low air velocities (0 < Ma< 0.2). The HM170 reaches a Mach number ofabout Ma = 0.1.

As open wind tunnels feature negative pressure inthe measurement section, the section must beclosed.

On the other hand , if higher velocities are required,then a closed wind tunnel can be used. Since inthese wind tunnels the measurement sectionrepresents the ambient pressure, the measure-ment section can be open. Closed wind tunnelshave an advantage in that less energy is requiredthan in an open wind tunnel due to the closed-cir-cuit air routing. However, they need more space toaccomodate and higher cost to produce.

1 2 3 4 5

Open wind tunnel

Closed wind tunnel

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2 Technical description 2

2.1 Function of the wind tunnel

The air is drawn in from the atmosphere via thestreamlined funnel (1).

Any transverse flow components are filtered out inthe flow straightener (2). It is made of a tubularhoneycomb structure. The air exits from the flowstraightener as a parallel flow and is accelerated toroughly 3.3 times its original velocity in the jet (3).

The static pressure (4) is measured downstreamof the jet at the entrance to the measurementsection. Based on the assumption of virtually loss-free flow, the flow velocity can be determined fromthe pessure difference with respect to ambientpressure (total pressure at zero velocity).

The air then flows through the measurement sec-tion (5) which has a constant cross-section.

After the measurement section the flow is de-celerated in a diffuser (6) and part of thepressuredrop required to accelerate the air inthe jet is recovered. The diffuser angle isdesigned in a way to prevent flow separation.

An axial fan (7) with downstream guide (8) drawsthe air out of the diffuser and conveys it into theopen.

1 2 4 5 6 9 7 8 10

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2 Technical description 3

A guard (9) in front of the fan prevents damagecaused by foreign matter or models, whereas theguard (10) behind the fan prevents contact withthe fan when it is in operation.

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2 Technical description 4

2.2 Design

2.2.1 Wind tunnel

Funnel (5), jet (3) and diffuser (6) are made ofglass-fibre reinforced plastic.

To provide access to the closed measurementsection, the sliding guide (12) permits adjustmentof jet and funnel (3, 5) together with the measure-ment section (2).

The flow straightener (4) has a tubular honeycombstructure.

The measurement section (2) is made ofperspex glass.

The axial fan (7) is provided with a downstreamguide which makes it highly efficient and producing

5 4 3 2 1 6 7

12 8 9 10 11

13

1 Model2 Measurement section3 Jet4 Flow straightener5 Funnel6 Diffuser7 Axial fan

8 Electronic two-component force transducer9 Measurement amplifier with force display10 Inclined-tube manometer for air speed11 Switch box with fan speed control12 Guide for moveable jet13 Laboratory trolley with drawers

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2 Technical description 5

low noise. The fan is driven by a three-phase ACmotor. A frequency converter (11) permits infiniteadjustment of rotational speed and thus air veloci-ty. The fan is rigidly connected to the diffuser andboth are attached to the laboratory trolley usingrubber elements. This effectively provides a shiel-ding of vibrations and guarantees extremelysmooth running.

The switch box (11) contains main switch, emer-gency stop, speed control and fan switch are loca-ted in .

The models (1) are attached to the electronic two-component force transducer (8). The values fordrag and lift are displayed digitally on the meas-urement amplifier (9) with two sensitivity settings.

The inclined-tube manometer (10) is used toindicate the current air speed at the entrance to themeasurement section.

The wind tunnel is installed on a laboratory trolley(13) that is easy to move. The trolley is providedwith shelves and lockable drawers for storing mea-suring instruments, models and other materials.

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2 Technical description 6

2.2.2 Force measurement

The flow forces at the model are measured elec-tronically in this wind tunnel.

For this purpose the wind tunnel is provided with apermanently installed electronic two-componentforce transducer beneath the measurement sec-tion.

The forces are converted via the lever arm of themodel holder (1) into proportional moments whichdeform a bending and torsion beam (2). Thedeformation is measured with a strain gauge (3)and displayed digitally as force on a two-channelmeasurement amplifier (7).

There is relatively little deformation, so that theposition of the model in the flow is scarcelyinfluenced. The angular position of the model(angle of attack at aerofoil) in the flow is set bymeans of a graduated dial (6).

The flexible measurering beam an the modelholder form an oscillatory system that maygenerate unwanted vibrations of the measuringdevice. The model holder is equipped with apistion-shaped shoulder (4) located beneath themeasurement beam and dipped into a viscous-oil-filled vessel (5). Damping of unwanted oscillationsis generated by trapped flow in the gap betweenthe pistion and the vessel.

Lift FA

via bending

Drag FW

via torsion

Principle of force measurement

1

6 2 3

FA

FW

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2 Technical description 7

3 Safety

DANGER of electric shock

Pull mains connector before opening switch box.Switch box is only to be opened by qualified per-sonnel.

DANGER of electric shock

Pull mains connector before opening measure-ment amplifier. Housing is only to be opened byqualified personnel.

DANGER OF INJURY caused by rotating impeller

Never operate wind tunnel without guards at faninlet and outlet.

ATTENTION

Never place moveable objects in front of windtunnel inlet and outlet. Strong suction!

Inflow and outflow of air must not be hindered inorder to achieve rated performance.

On installation, comply with following minimumdistances from walls or other objects:

- Intake: 1 m

- Fan outlet: 2 m

ATTENTION

Lock rollers of laboratory trolley. Wind tunnelmay develop thrust of up to 100 N.

1 m 2m

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3 Safety 8

ATTENTION: Lock jet properly with the catch(1) during operation.

Jet may otherwise abruptly open forwards dueto the negative pressure at the inlet.

ATTENTION: Close lower opening in measure-ment section with slide.

Entry of secondary air will otherwise preventachievement of rated wind tunnel performance.

ATTENTION: Do not overload force transducer.

Measuring ranges:

Lift FA: 10 N

Drag FW: 3 N

ATTENTION: Programming of frequency conver-ter must not be altered without consultingG.U.N.T.

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3 Safety 9

4 Commissioning and operation

4.1 Installation

Rated performance is only possible if there is anunhindered inflow and outflow of air. As the airin the installation area flows from outlet to inlet,a sufficiently large space (> 150 m3) must beselected in order not to influence the flowconditions.

The following minimum distances from walls orother objects are to be ensured on installation:

- Intake: min. 1 m

- Blower outlet: min. 2 m

The wind tunnel has a considerable suctioneffect. Lightweight, loose objects should not bepositioned in front of the inlet.

The wind speed at the outlet reaches up to 100km/h. Lightweight or loose objects are thus not tobe positioned in the vicinity of the outlet.

As the wind-tunnel thrust may reach 100 N, thebrakes on the laboratory trolley rollers are to beapplied to stop the wind tunnel rolling away.

Appropriate fusing is to be provided for the mainsconnection. (e.g. 16A for 230V)

min.1 m min. 2 m

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4.2 Commissioning

4.2.1 Checking inclined-tube manometer

- Align manometer horizontally using spirit level.

- Fill manometer with the supplied red liquidprovided up to the zero mark on the scale.

- Finely adjust zero mark by moving the scale inthe slots.

- Check hose connection between end ofinclined tube and measurement socket atwind tunnel.

4.2.2 Removing the transport safety device

The transport safety device prevents the jet fromopening during transport.

Remove green transport safety device (1) at thejet-guide shafts.

4.2.3 Opening and closing measurement section

To have access to the interior of the measurementsection, push the measurement section with the jetforwards. The measurement section is locked in theclosed position with a pin.

Opening measurement section

- Pull pin (1) upwards and push measurementsection (2) forwards.

- With model fitted, lower closure plate (3) ispushed backwards out of slot by modelholder (4). 1

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Closing measurement section

- Insert closure plate (3) in slot of measurementsection (2) and pull measurement sectionbackwards until pin (1) engages.

- With model fitted, first pull measurement sec-tion backwards until model holder (4) is at startof lower slot. Then insert closure plate (3) andcompletely close measurement section (2) untilpin (1) engages.

ATTENTION: Measurement section must be pro-perly locked in position by engagement of pin.

Otherwise there is a danger of sudden opening ofthe measurement section during operation.

4.2.4 Operation of fan

All fan controls are located in the switch box.

- Emergency stop switch (1)

- Main switch (2)

- Fan switch (3)

- Fan speed control (4)

ATTENTION: Before starting the fan first check thefollowing:

- No loose objects (models, fastening screws,covers etc.) in jet, measurement section ordiffuser

- Closure plate inserted

- Measurement section closed and locked

- Emergency stop switch released (pull red knob)

- Speed control on zero

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4 Commissioning and operation 12

- Turn the unit on using the main switch (2)

- Switch on fan (3)

- Use speed control (4) to increase slowly fanspeed. Observe inclined-tube manometer andset desired speed.

- Speed control setting 10.0 (max.) should pro-duce 28 m/s.

ATTENTION: Secondary air caused for exampleby absence of closure plate will reduce wind-tunnelperformance.

Then max. speed would not be reached.

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4.3 Speed measurement

4.3.1 Measurement with built-in instrument

The air speed is measured at the entrance to themeasurement section. The static pressure ps inthe duct is tapped by means of four holesdistributed around the periphery of the duct.

The difference in pressure between total and staticpressure corresponds to the dynamic pressure pd

and is proportional to the square of the flowvelocity.

Assuming negligible pressure losses, the totalpressure pg in the duct is equal to the total ambientpressure pu . This raises the need for pitot tubesin the duct which would influence the flow field.

With density ρ of air, speed is thus:

v = √2 pd

ρ = √ 2 (pu − ps)

ρ = √2 ∆p

ρ.

Height h of liquid column in inclined-tube manometergives

∆p = ρfl g ∆h.

where ρfl is the density of the liquid.

v = √ 2 ρfl g ∆h

ρ .

Direct speed readings can be taken by means ofa scale calibrated in m/s on the manometer.

ps, v

pu, vu =0

∆h ≈ ∆p

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4.3.2 Measurement with Prandtl tube

If available,a Prandtl tube may also be used tomeasure the speed.

Such a tube is a combination of a pitot tube formeasuring the total pressure and a measurementpoint for measuring the static pressure. The twopressures are transfered to a differential pressuregauge (3) by means of a double-walled tube.

The measurement point (1) for the total pressureis on the end face of the probe to which the flow isapplied. Further measurement bores (2) areuniformly distributed around the periphery formeasuring the static pressure. Taking themean value of the peripheral points will minimizea possible oblique flow.

The speed is calculated as follows

v = √ 2 ρfl g ∆h

ρ .

The probe should be parallel to the flow whenPrandtl tube is used for measurement.

2

3

1

∆h

Static pressure ps

Total pressure pg

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4.3.3 Calibration of speed measurement

The built-in speed measuring device can be cali-brated if a Prandtl tube is available.

Due to pressure losses in the inlet, the flowstraightener and the jet, the total pressure at themeasurement point does not exactly correspondto the ambient pressure. Allowance for theresultant measurement error can be made bya correction factor.

The current air density must be known for precisemeasurement. This is taken from tables on thebasis of known atmospheric pressure, relativehumidity and temperature, e.g.

Atmospheric pressure: 1013 mbar

Rel. humidity: 60%

Temperature : 20 °C

Density : 1.199 kg/m3

Measurement is to be performed as follows:

- Remove any models from the measurementsection.

- Close off lower slot of measurement section (1)with slide (5).

- Close and lock measurement section.

- Connect Prandtl tube (2) to second inclined-tube manometer (3).

- Align the manometer (3) horizontally and setzero point.

- Set wind-tunnel speed at 20 m/s.

- Insert Prandtl tube (2) into measurement sectionthrough 13mm-hole (4) on its side.

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- Use Prandtl tube to take measurements atvarious points in flow cross-section and notedown pressures. Ensure sufficient wall clea-rance (min. 50 mm). Do not take measure-ments in the vicinity of fastening holes.

- Make sure Prandtl tube is aligned in parallel tothe flow.

- Using the mean values displayed and determi-ne with current density the speed

v0 = √ 2 ρfl g ∆h

ρ .

- Calculate correction factor at speed v of thebuilt-in instrument

k = (v0 ⁄ v) 2.

Corrected speed is thus

vcorr. = √k v 2 .

Repeat measurement for other speeds and checkcorrection factor.

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4.4 Installation of models

Aerodynamic models for which a force measure-ment is to be performed must have a model holderwith a shaft diameter of Ø4 mm.To obtain the correct lever arm for the forcemeasurement, the length of the holder should be190 mm measured from the centre of the model.This simultaneously positions the model in thecentre of the measurement section.

- Before inserting model in two-componentforce transducer, set angle scale to zero.

- Insert model and carefully secure with upperknurled screw.

In doing so, set model to a distance of exactly302 mm between centre of bending beam andcentre of model. The force measuring device iscalibrated to this lever arm.

- Set desired angle of attack by loosening thelower knurled screw and turning the angle scale.Re-tighten knurled screw.

225 mm Ø 4mm

Ø2 x 12 mm

190 mm

x

View X

302 mm

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Other models and devices, such as instabilitymodel for aerofoils, models for investigatingboundary layers or different measurement probescan be attached to the holes in the measurementsection.

Side

Top

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4.5 Force measurement

4.5.1 Force transducer

The flow forces at the models are measured by anelectronic two-component force measuring de-vice.

This device consists of a force transducer and ameasurement amplifier with display.

The forces FA (Lift) and Fw ( Drag) are converted bymeans of the lever arm a of the model holder intoproportional moments M, which deform a bendingand torsion beam.

The deformation is measured with a strain gaugeand displayed digitally on the two-channel ampli-fier as force.

Lever arms other than a=302 mm involve correc-tion of the displayed force F.

Fcorr. = F ⋅302

a with a in mm

The following force directions are conventionally-defined as positive (top view):

a

Moment M = F a

F

Lift+ FA Drag

+ Fw

Lift via bending

Drag via torsion

FA

FW

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4.5.2 Measurement amplifier

The measurement amplifier contains two bridgeamplifiers with variable gain. These amplifierstakes their input from the strain-gauge full bridgesin the force transducer.

The output voltages are directly indicated on twodigital displays as lift (1) and drag (2) in N. Zerocalibration of the displays can be performed withtwo offset potentiometers (3, 4). Tare setting isthus also possible. Sensitivity can be altered by aswitch (5) by a factor of 10.

The measurement amplifier is connected to theforce transducer via a 8-pole cable.

The mains switch (6) is on the back.

The unit should be allowed to warm up for roughly30 min. prior to measurement. Zero calibration ofthe display is then performed.

4.5.3 Error due to influence of dead weight

In the case of models with support outside thecentre of gravity, there is an additional error

indication caused by the effect of weight G ⋅ s.

As this error is static, compensation can beprovided by means of zero balancing in stationarycondition with model fitted.

2 4 5

1 3 6 on back

Error due to effect of weight

M = F a - G s

a

s

F

G

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4.5.4 Error caused by model holder

The drag of the model holder may bias the meas-urement.

As the error is a function of speed, it does not occurin stationary condition and cannot be equalised bymeans of offset balancing.

Compensation involves the following steps:

- Fit holder without model.If holder is permanently connected to model, fitsubstitute holder with same geometric dimen-sions.

- When the measurement speed is reached,measure the drag.

- Fit model and repeat measurement at samespeed.

The difference between the two measurementsgives the net drag force at the model.

Fw = FG − FH

Holder only,no model

With model

FH

FG

v= const.

v= const.

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5 Experiments

A simple experiment is outlined here. Other in-teresting experiments are contained in the in-structions for G.U.N.T. accessories.

The experiment involves determination of the dragcoefficient cw on a simple circular disc.

The drag on an object subjected to flow can becalculated using the following equation

Fw = 12 ρ cw A v 2 .

Drag increases with the square of the velocity.

Furthermore, it is governed by the density ρ of theair, the projected area A of the object and the dragcoefficient cw, which reflects the influence oftheobject’s shape, but is independent of its size.

If cw is known, drag can be calculated in advancefor any body. The drag coefficient can be determin-ed from the drag at given velocity

cw = 2 Fw

ρ A v 2 .

A circular disc of 80 mm diameter is installed in themeasurement section at right angles to the di-rection of flow.

The drag is measured at 25 m/s

Fw = 2.23 N .

The projected area of the end face is

A = d 2 π 4 =0.08 2 π

4 = 5.02 10−3 m 2 .

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With T = 18°C, p = 1026 mbar and a relativehumidity level of 60% the air density is

ρ = 1.225 kg/ m3 .

The drag coefficient can be thus calculated

cw = 2 Fw

ρ A v 2 = 2 ⋅ 2.23 N

1.225 kg/m3 ⋅ 0.00502 m2 ⋅ 252 m2/s2

cw = 1.16 .

This value is comparable to the value (1.10) foundin the literature.

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6 Appendices

6.1 Technical Data

General dataDimensions L x W x H : 2850 x 750 x 1700 mm3

Weight: 250 kgPower supply: 230 VAC, 50 Hz, 1ph

Alternatives optional, see type plateMeasurement section Cross section: 292 x 292 mm2

Lenght: 450 mm

Force measurement Model holder, dia. 4 mm Model holder, lenght to centre of model:

225 mm Lever arm, centre of model to bending beam of force transducer: 302 mm

Side

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Measurement ranges: Lift: 10 N Drag: 3 N Resolution: 0.01 NDisplay: 3 1/2 digitSwitchable gain: x1, x 10

Offset adjust: ± 50 % FS

Air flowAir velocity (adjustable): 0 to 28 m/s

Irregularity of velocity ± 2 %(for a measurement section of 200 x 200 mm2)

-200 mm 0 mm 200 mm horizontal

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Velocity distribution across the working section

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FanHead: 500 PaMax. air flow: 2.5 m3/sBlower wheel dia.: 400 mmMotorpower: 2.25 kW Speed (variable freqency control):

0 to 2800 RPM

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6.2 List of symbols

a Length of lever mA Area m2

cw Drag coefficientd Diameter mF Force NFw, FA Drag, Lift Ng Accelaration due to gravity m/s2

G Weight Nh Head mk Velocity correction coefficientM Moment Nmp Pressure N/m2

s Distance to centre of gravity m

ρ Density kg/m3

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6.3 Index

AAngle of attack, adjustment. . . . . . . . . . . . . . . . . . . . . 7, 18Axial fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3, 5

CClosed wind tunnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Commissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

DDamper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Diffusor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3, 5Drag. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Drag coefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

EEiffel type wind tunnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

FFan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Fan, operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Flow straightener. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Force directions, definition . . . . . . . . . . . . . . . . . . . . . . . 20Force measurement . . . . . . . . . . . . . . . . . . . . . . . . . . 7, 20Force transducer . . . . . . . . . . . . . . . . . . . . . . . . . . . 6, 7, 20Frequency converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Function of wind tunnel . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Funnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3, 5Fusing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

IInclined-tube manometer . . . . . . . . . . . . . . . . . . . 6, 11, 14Inflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Influence of dead weight . . . . . . . . . . . . . . . . . . . . . . . . . 21Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Installation of models . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

JJet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3, 5

LLaboratory trolley . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Lift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

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MMeasurement amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . 21Measurement section . . . . . . . . . . . . . . . . . . . . . . . . 2, 3, 5 , dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 , locking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 , opening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Measuring ranges force transducer . . . . . . . . . . . . . . . . . 9Model holder, error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 , length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

OOffset adjust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Open wind tunnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Outflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

PPrandtl tube. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15, 17Prechamber. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

SSafety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Speed correction factor . . . . . . . . . . . . . . . . . . . . . . . . . . 17Speed measurement, build-in instrument . . . . . . . . . . . . 14 , calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 , Prandtl tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Switch box. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

TTechnical data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Technical description . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Transport safety device. . . . . . . . . . . . . . . . . . . . . . . . . . 11

VVelocity distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

WWarm up measurement amplifier . . . . . . . . . . . . . . . . . . 21

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