Is there an Aerodynamicist in the house?

[rtcosic]

Replaced cheap and nasty white plastic exhaust vent with a shiny Stainless Steel one.

Who can resist shiny Stainless Steel?

But with the cooker hood at its higher settings, my louvres are all of a flutter.

Add mass?

More sophisticated solution? Little teeny tiny trim tabs? Something else?

I have a video. How do I post it?

 

[angellonewolf]

did it work ok with plastic vent ?

inline fan to add more air flow ?

flaps to heavy ?

 

[angellonewolf]

add a vid to youtube then post a link in the thread

 

[Screwdriver]

Is it a large square panel fixed at four corners?

 

[zx9]

I have a video. How do I post it?

No idea about the real question but the last one is:
Put it on YouTube and add a link in this thread.

 

[MichaelV]

Replaced cheap and nasty white plastic exhaust vent with a shiny Stainless Steel one.

Who can resist shiny Stainless Steel?

But with the cooker hood at its higher settings, my louvres are all of a flutter.

Add mass?

More sophisticated solution? Little teeny tiny trim tabs? Something else?

I have a video. How do I post it?

Not at all an aeroelastics expert, but you’re right to suggest added mass. Often the handiest way to alter modal response and eigenvalues.

It’s possible your change to stainless increased stiffness, so adding mass might get you back into a less responsive interval between modes.

 

[gaz1]

id put an inline fan if i was you

either way it dosnt read as either will work and it best to use something with a little more push

to be honest cooker fans are not that good and more so when blowing outside

 

[rtcosic]

did it work ok with plastic vent ?

inline fan to add more air flow ?

flaps to heavy ?

Yes

Flow too high for these louvres

Louvres too light rather than too heavy.

Youtube upload in progress.

 

[rtcosic]

add a vid to youtube then post a link in the thread

In progress

Is it a large square panel fixed at four corners?

Yup, that's the puppy:

Stainless Steel Wall Air Vent Extractor Fan Grille & Non Return Flaps 150mm 6" | eBay UK

Kitchen Appliance Spares. Car & Caravan Accessories. Whether youre looking for vacuum cleaner parts, tumble dryer spares, dishwasher or washing machine components, or even microwave and cooker hood accessories, weve got you covered.

www.ebay.co.uk

 

[rtcosic]

Not at all an aeroelastics expert, but you’re right to suggest added mass. Often the handiest way to alter modal response and eigenvalues.

It’s possible your change to stainless increased stiffness, so adding mass might get you back into a less responsive interval between modes.

Argh! Haven't played with eigenvalues since c. 1972. You will be threatening me with Laplace transforms next. I never understood those either.

I plan to experiment with Blu Tack.

I had visions (dreams?) of adding little teeny tiny spoilers on the trailing edge of the louvres. Or something equally pointlessly complex.

 

[rtcosic]

Starts at Fan setting 3 then up to max of 5 and back to 3. No issues at 1 and 2 of course

 

[Screwdriver]

Lolz.

 

[angellonewolf]

weld a metal one up

 

[Seadog]

Poor pipe run/abrupt change of dimension near the terminal causing turbulence, perhaps.

 

[Screwdriver]

I might try connecting them together with a bit of wire. They are “beating“ as each individual element disturbs the air to the other.

you may find that connecting the middle two together will calm the whole thing down. Does look hilarious though. Thanks for that!

 

[brightspark]

use an inline backdraught shutter and a plain grill Manrose Round Backdraught Shutter 4 Inch 100mm (electricpoint.com)

 

[rtcosic]

Poor pipe run/abrupt change of dimension near the terminal causing turbulence, perhaps.

Not really. Straight shot to the vent of at least 2 metres. Admittedly it's the spiral wound thin stuff not smooth bore. I think it's because these louvres are either lighter than the plastic ones or a poor aero shape - or both.

 

[MichaelV]

Argh! Haven't played with eigenvalues since c. 1972. You will be threatening me with Laplace transforms next. I never understood those either.

I plan to experiment with Blu Tack.

I had visions (dreams?) of adding little teeny tiny spoilers on the trailing edge of the louvres. Or something equally pointlessly complex.

Hmmm… seeing the video, it’s more like vortex shedding/flutter at higher flow rate. Add the Blutack and see if you can dampen it.

As to your temptingly exotic suggestion of adding spoilers or strakes… the agricultural approach would be to take the snips to the trailing edges and cut/twist loads of wee distorted serrations. But might spoil the look!

 

[rtcosic]

use an inline backdraught shutter and a plain grill Manrose Round Backdraught Shutter 4 Inch 100mm (electricpoint.com)

If I can't solve it I'll stick the 150mm plastic version of this back on.

Manrose Flap Vent White 125mm x 125mm - Screwfix

Order online at Screwfix.com. HIPS polystyrene. Suitable for commercial and domestic use. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

 

[tom2207]

bit of all round banding or the likes from top to bottom and about half inch off the flaps , sorted .
stainless band and a bit of tank strap , only thinking out loud here .