Post on 18-Dec-2014
description
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
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Introduction
What we are doing? Laminar flow control Wind tunnel turbulence level Flat plates Wavy plates
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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
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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
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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
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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
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Wind Tunnel Turbulence Level
Sphere Test Set up Manufacturing Results
Hot Wire Test Set up Manufacturing Results
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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.
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Sphere Test
Manufacturing
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CAD MODEL - BRACKET
Sphere Test
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BRACKET and TEST SET UP
Sphere Test - Results
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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%
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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
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Hot Wire Test
Manufacturing
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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.
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Hot Wire Test - Results
VELOCITY (m/s) TURBULENCE INTENSITY (%)10 0.01415 0.01420 0.01525 0.01930 0.015
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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.
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Flat Plate Design
The flat plate will be tested for transition point
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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.
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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.
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THANK YOU FOR LISTENING
ANY QUESTIONS?