MENG AEROSPACE ENGINEERING

LAMINAR FLOW CONTROL

Supervisor: Dr Jian Wang

Mandeep PhullCecil Ng

John Gane

03/06/2010

Presentation Content

Introduction Why?, What?, How?

Aims and Objectives Wind Tunnel Turbulence Testing

Sphere Test Set up – manufacturing – results

Hot wire Test Set up – manufacturing - results

Flat & Wavy Surface Models Test Specification Model Specification

2/21

EGM064: Group Project

Introduction

What we are doing? Laminar flow control Wind tunnel turbulence level Flat plates Wavy plates

3/21

EGM064: Group Project

Why?

Background Laminar flow control

Laminar flow Boundary layer forms Smooth flow

Transition Point in which laminar

flow turns to turbulent Turbulent

Contains eddying motions

Mechanical energy in flow goes into formation of eddies

Higher drag

Ref:http://www.aviation-history.com/theory/lam-flow.htm

4/21

EGM064: Group Project

Why?

LFC Not new technology

P-51 WWII Natural laminar airfoil section Developed by NASA Outstanding speed and range

A lot of research has been carried out Never enough interest

Benefits Reduce CO2 emissions Reduce fuel burn Reduce drag LFC

EGM064: Group Project

5/21

What?

Aims and objectives Measure turbulence level of wind tunnel

Sphere test Hot-wire Test

Carry out transition measurements on flat plate with/without pressure gradient

Carry out transition measurements on wavy plate with/without pressure gradient

Design and manufacture the sample of flat plate Conduct experiments and numerical simulations

on effects of wavy surfaces and flat plates on laminar flow and transition

Validate the numerical model

6/21

EGM064: Group Project

How?

Methodology Measure turbulence level

Turbulent spheres Design bracket to mount spheres to support arm

Hot wire test Design bracket to mount probe Design bracket to use in Traverse system

Design the flat plate Design the wavy plate Investigate effects of wavy surface on laminar

flow and transition experimentally and numerically

Computational Fluid Dynamics

7/21

EGM064: Group Project

Wind Tunnel Turbulence Level

Sphere Test Set up Manufacturing Results

Hot Wire Test Set up Manufacturing Results

8/21

EGM064: Group Project

Sphere Test

Set-up There were 3 different sized

spheres (6”, 8”, 10”)

The spheres were mounted in the wind tunnel attached to a 6 axis balance capable of measuring drag

There was no existing method to mount the spheres, so needed to manufacture a support or bracket, making sure the sphere would be mounted parallel to the incoming flow.

EGM064: Group Project

9/21

Sphere Test

Manufacturing

EGM064: Group Project

10/21

CAD MODEL - BRACKET

Sphere Test

EGM064: Group Project

11/21

BRACKET and TEST SET UP

Sphere Test - Results

EGM064: Group Project

12/21

Results from Wind Tunnel test

Sphere Test - Analysis

The average critical Reynolds Number for all spheres was 225,000 for a CD value of 0.3.

TF = 385,000/Rec = 1.71

This was Turbulence factor compared to a graph to find intensity.

The intensity of the wind tunnel was found to be 0.9%

EGM064: Group Project

13/21

Hot Wire Test

Set-up The hot wire probe uses a small wire with a

current running through it, the rate at which it cools determines the speed of the air flow

The hot wire probe and anemometer was provided courtesy of our supervisor

The same problems arise of finding a means of mounting it into the flow

EGM064: Group Project

14/21

Hot Wire Test

Manufacturing

EGM064: Group Project

15/21

Hot-wire test procedure

Setup We used the traverse to map a 7x7 grid of

the wind tunnel measuring mean velocity.

A velocity profile was built of the working section of the wind tunnel.

Turbulence testing was then completed by taking readings in the middle of the test cell at different velocities.

EGM064: Group Project

16/21

Hot Wire Test - Results

VELOCITY (m/s) TURBULENCE INTENSITY (%)10 0.01415 0.01420 0.01525 0.01930 0.015

EGM064: Group Project

17/21

VELOCITY (m/s) TURBULENCE INTENSITY (%)

10 0.013

15 0.017

20 0.017

25 0.020

30 0.017

With the hole not covered

With the hole covered

Hot Wire Test - Analysis

The turbulence level read out by the hot wire is far too low compared to the turbulence spheres.

Lack of experience

Turbulence sphere test is more likely to be correct.

EGM064: Group Project

18/21

Flat Plate Design

The flat plate will be tested for transition point

EGM064: Group Project

19/21

Flat Plate Manufacturing

Cannot be completed in the Kingston University labs due to machine sizing and tolerances.

A quote was given by a specialized engineering company of £2000 (JNDC) for manufacturing.

Due to lack of money and facilities for construction the flat plate was not built.

EGM064: Group Project

20/21

Conclusions

From the first wind tunnel test it was concluded that the turbulence level was 0.9%.

Following on from this, the second wind tunnel was set up using hot wire anemometer. The turbulence level derived was at 0.02%

There is a big discrepancy between the two tests hence requiring further testing.

EGM064: Group Project

21/21

THANK YOU FOR LISTENING

ANY QUESTIONS?