Institute of Engineering

TRIBHUVANUNIVERSITY

INSTITUTE OF ENGINEERING

PULCHOWK CAMPUS

Complete design of a Wind Tunnel

By:

Anuj Shrestha (060BME604)

Manish Rijal (060BME614)

Santosh Sharma (060BME632)

A

PROPOSAL PROJECT

SUBMITTED TO THE DEPARTMENT OF MECHANICAL ENGINEERING

IN PARTIAL REQUIREMENT OF THE REQUIREMENTS OR THE

DEGREE OF THE BACHELOR OF ENGINEERING

DEPARTMENT OF MECHANICAL ENGINEERING

LALITPUR, NEPAL

Chaitra, 2063 B.S.

TITLE OF THE PROJECT

INTRODUCTION

TECHNICAL DESCRIPTION AND ITS FUNCTIONAL CHARACTERISTICS

OBJECTIVE

LITERATURE REVIEW

METHODOLOGY

EXPECTED OUTCOMES OF THE PROJECT

PRINCIPAL BENEFICIARIES OF THE PROJECT

ESTIMATED EXPENDITURE

CONCLUSION

TITLE OF THE PROJECT: Complete Design of Wind Tunnel.

1.0 INTRODUCTION:

The characteristics of wind, variation of its pressure and speed are the interest of many peoples all around the world. Many people are studying the effects of air moving over or around solid objects and at different speed. They do this in a Wind tunnel. Thus the "Wind tunnel" is a facility, by artificially producing airflow relative to a stationary body that measures aerodynamic force and pressure distributionto simulate with actual conditions.

There has been a lot of interest in the field of aerodynamics in Nepal. Many research works has been done bymany institutions. But due to the lack of aerodynamic test equipment effective results were not achieved. Also students’ interest towards this field couldn’t be attracted satisfactorily.This is due to the fact that they don’t find even the basic test equipment to enlighten and strengthen their interests. Thus the country is unable to produce higher qualified manpower in this field.

Proposed project would help any institution or individual to make a wind tunnel of their own and perform the required aerodynamics test.

2.0 TECHNICAL DESCRIPTION AND ITS FUNCTIONAL CHARACTRISTICS:

Theprobable size of wind tunnel under our design consideration is shown in the figure below:

The dimensions of the wind tunnel may vary while considering the economy and simplicity. The settling chamber consists of honeycomb to minimize turbulence. Provisions for transparent window are there in the test section. And the drive section consists of the axial fan.The wind tunnel is designed to have a wind velocity around 40m/s (144 km/hr) in the test section. To do so a compression ratio of 1:3 is used. This means an axial wind fan of about 36inch blade diameter which can generate a speed of 13.33m/s should be used.

3.0 OBJCTIVES

• To form a basis for complete design of a wind tunnel.
• Studying the characteristics of flow in the tunnel. Calculating the losses in tunnel.
• Studying the effect of winds in various structures.
• The building of 1:3scale prototypes would help to eliminate the obstruction and minimize the problem that may be encountered during the installation of the full scale wind-tunnel. Also the prototype can be used in the department as a laboratory equipment to do different tests in the field of aerodynamics.
• The completion of project would accelerate the interests of individual and institutions in the field of aerodynamics.
• Also this wind tunnel project is to provide a hands-on creative problem-solving experience that incorporates the necessary elements of a design project.

4.0 LITERATURE REVIEW:

A wind tunnel is a device in which a jet of air or any other suitable gas of uniform properties across the cross section is produced. A wind tunnel simulates the conditions of an aircraft in flight by causing a high-speed stream of air to flow past a model of the aircraft (or part of an aircraft) being tested. This is used for aerodynamically testing the model under the given standard conditions.

All the wind tunnels are generally comprised of the driving unit, a settling chamber, an acceleration duct (either contraction or nozzle) the test section and the diffuser. The driving unit consists of fan, blower or a compressor generally driven by an electric motor. The location of the driving unit depends on the type of the tunnel. The flow from the blower or compressor or a fan is settled in a large chamber called the settling chamber. This is provided with wire gauzes and arrays of honeycombs to straighten the flow and remove irregularities in it. The settling chamber supplies the flow to the contraction. This is carefully designed to accelerate the flow from the settling chamber to the test section velocity with minimum disturbance.

The contraction or the nozzle feeds the test section with suitable jet of uniform velocity. The model to be tested is fixed here with suitable supports. The model is mounted on wires so that lift and drag forces on it can be measured by measuring the tensions in the wire. The paths of the air-stream around the model can also be studied by attaching tufts of wool (which align themselves with the wind direction) to various parts of the model, by injecting thin streams of smoke into the tunnel to render the airflow visible, or by using certain optical devices. A transparent window or strong glass is often provided on one or both the side walls of the test section. Pressures on the model surface are measured through small flush openings in its surface. Forces exerted on the model may be determined from measurement of the airflow upstream and downstream of the model. The diffuser collects the flow from the test section and raises the pressure of the air for discharging it into the atmosphere or the return circuit in case of closed circuit tunnel.

Wind tunnel test is a significant factor in any type of vehicle design, from airplanes including automobiles. It is important in the prediction of forces and moments in sailing. Structural engineers also use aerodynamics, and particularly aero-elasticity, to calculate wind loads in the design of large buildings and bridges. Urban aerodynamics seeks to help town planners and designers improve comfort in outdoor spaces, create urban microclimates and reduce the effects of urban pollution. The field of environmental aerodynamics studies the ways atmospheric circulation and flight mechanics affects ecosystems. The aerodynamics of internal passages is important in heating/ventilation, gas piping, and in automotive engines where detailed flow patterns strongly affect the performance of the engine.

5.0 METHODOLOGY:

The activities from the initiation to the finalization of this project involve some these processes:

• Initial paper Works: This includes the search for the entire text materials, booksabout the design of Wind tunnel from library to internet.Regular Teacher’s guidanceismost importantat this stage as this is the beginning. Then design processes for separate parts started. This includes rough sketches of different parts, small calculations etc.
• Studying about the axial fan:as our design is totally based in the speed and characteristic of air sucked by an axial fan. So it is most sensible unit of our project. So the study of the axial fan is done quite initially. During this we learn the size, cost, rpm, and speed characteristics of air delivered by an axial fan. This minimizes the change in design of the tunnel after the initial design if we get to know that we can’t find the desired characteristics’ fan.
• Design work:Design work refers to complete design of each component. Full calculation considering each and every aspect. From this we can have a detailed drawing of each chamber. This it-self is the complete design.In this step we choose the materials for each section.
• Building the prototype wind tunnel: Now for building the prototype we recalculate the size, as the prototype is 1/3 times than the actual sized wind tunnel. For that we first search for the axial fans. We will use an old one which most probably will be found in a junk-yard. Now we purchase and start the assembly of different parts of the prototype wind tunnel. We first perform pre-assembly i.e. assembly of small parts which are finally assembled together. After that we get a control system for the fan. This is because we need various speed for various experiment and this is done by the varying the rpm of the fan, this is done by the control system.
• Testing the wind tunnel: Now the prototype wind tunnel is tested if the flow inside it at various rpm of fan is within the range of design. To do that pitot probe is attached at different points. Velocity profiles are drawn and matched with the designed profiles. If the values come approximately same then the design is good. Also the type of flow and characteristics of flow inside of the tunnel is studied in detail.
• Optimization of Design:The next step after the testing is the optimization of design i.e. making the best and most effective. For that we look for the change in design and other options available to get the best performance of the prototype. The immediate outcome of the change in design is studied and if it’s not that effective then other options are used.
• Final Design:After we get satisfactory results from the optimization of our model we examine and change the initial design of the wind tunnel. After that we get new optimized complete design of the wind tunnel, with all necessary information in it. So from our complete design anyone can assemble the wind tunnel for their purpose.

Regular check and evaluation study of the progress of the project till that date is done monthly. This helps us to know how we are moving and what changes are desired.

Time line chart for the proceedings of the project:

activity / Chaitra / Baisakh / Jestha / Asar / Shravan / Bhadra / Ashwin / Kartik
1 / 2 / 3 / 4 / 1 / 2 / 3 / 4 / 5 / 1 / 2 / 3 / 4 / 1 / 2 / 3 / 4 / 1 / 2 / 3 / 4 / 1 / 2 / 3 / 4 / 5 / 1 / 2 / 3 / 4 / 5 / 1 / 2 / 3 / 4
initial paper work
study about axial fan
initial design work
building a proto-type wind tunnel
testing the wind tunnel
optimization of Design
final
design

6.0 EXPECTED OUTCOMES OF THE PROJECT:

This project will prove itself as a milestone in the field of aerodynamics research in Nepal.

This will strengthen the interest of students towards the field.

Studies and research can be done in the country itself about different aerodynamic problems.

This would open a new field in design of airfoils in the country itself.

7.0 PRINCIPAL BENEFICIARIES OF THE PROJECTS:

The principal beneficiaries of the product are all the individuals and institutions interested in this field. Especially students and teachers wishing to do something in the field of aerodynamics are benefited.