The Venturi Effect and other possible solutions

[sadie]

Maybe because there was no gust of wind when Kate came in through the patio door.    Amaral did say in his book it was windy at night.

It was gusty according to weather reports that I posted on here.   I seem to remember that gusts of 20
mph were recorded     These reports seem to have been wiped now.

[kizzy]

I don't know.  I'm not a scientist.

I do know what the witness said in her statement correctly described what happens in such circumstances and I do know that a diagram illustrating the effect was posted on the forum at one time.
And if you are really interested the internet is full of them.

Slamming of doors by a draft
The slamming of doors due to a draft, is also due to the Venturi effect.
The door gap is a constricted cross-section through which the air flows very quickly.
The air pressure in the gap between the door and the frame drops.
Around the door leaf, the air usually flows at a much lower speed.
The higher pressure on the door leaf compared to the air pressure in the gap, therefore slams the door with great force, even if the air stream flows with the opening direction of the door! https://www.tec-science.com/mechanics/gases-and-liquids/examples-of-applications-of-the-bernoulli-effect/

I don't know.  I'm not a scientist.


No, so you dont know either why it didnt slam when the patio door was opened.

[sadie]

I don't know.  I'm not a scientist.


No, so you dont know either why it didnt slam when the patio door was opened.

I do.    Reasons:

1)  The patio door opening didn't happen the same time as a gust outside
2)  The bedroom door was wide open when Kate entered via the patio door and for the venturi ffect to take place, the gap between door and surround had to be minimal.
3)   If the bedroom door was open so that it lined up with the corner of the wardrobe, then none of the back face of the door had any wind on it.   The back face of the door was in the Lee of the corner of the wardrobe.



Item 2 is the most likely.   The conditions re gap where not suitable for a Venturi reaction.


It wa only as the gap betwixt door and frame narrowed that the Venturi effect came into operation.

[Brietta]

Maybe because there was no gust of wind when Kate came in through the patio door.    Amaral did say in his book it was windy at night.

There was a lot of puzzling over the years of exactly the circumstances in which Kate's description of events could have occurred and I think the members of this forum worked it out.

First of all an air flow was found which Pegasus got quite excited about.

http://www.allmystery.de/i/t79bd1b_the-ocean-club-appartments-in-praia-da-l.jpg
Eureka. Found the through draught.
See that 3-storey-high vent chimney on the left of the building. You can see it continue down the wall. That must connect to the cooker vent hoods in the kitchens of 5A and 5G and 5K.

So air flows in the open child bedroom window and out the vent hood in the kitchen and up that vent chimney.

The gravity effect will make the through draught even stronger.
So there folks you have your slamming door and blowing curtains, exactly as truthfully described by the witness.https://miscarriageofjustice.co/index.php?topic=5409.msg195465#msg195465

[Brietta]

I don't know.  I'm not a scientist.


No, so you dont know either why it didnt slam when the patio door was opened.

I can read both what has been posted on this forum and from scientific data posted on the internet to work out that what Kate described happened very much as she said it did.

Perhaps one requires to have an open mind to do that and the knowledge that I don't know everything ~ but I am willing to learn.

And so very often gems of knowledge used to be posted on this forum which as time goes by get forgotten or as new members arrive ~ are not known about.

Barrier had never heard of the Venturi Effect in relation to Kate describing witnessing it, for example.  Well he has now!

[Brietta]

I do.    Reasons:

1)  The patio door opening didn't happen the same time as a gust outside
2)  The bedroom door was wide open when Kate entered via the patio door and for the venturi ffect to take place, the gap between door and surround had to be minimal.
3)   If the bedroom door was open so that it lined up with the corner of the wardrobe, then none of the back face of the door had any wind on it.   The back face of the door was in the Lee of the corner of the wardrobe.



Item 2 is the most likely.   The conditions re gap where not suitable for a Venturi reaction.


It wa only as the gap betwixt door and frame narrowed that the Venturi effect came into operation.

Sadie - I replied to the wrong post and not yours above. Don't be concerned if you've seen it and are worrying about what I'm getting up to - just me getting mixed up ;)

[Brietta]

Sigh. I did try telling you before, if you stop making easily contestable statements & presenting your opinion as fact in your posts every time, I wouldn't feel compelled to reply.
If you'd have said physics supports Kate's account, rather than proves it, you might not have heard from me.

I should be so lucky!

However ignoring insults and back to the thread topic of the information secreted within forgotten forum posts. Which really should be remembered for their veracity and honest attempts at finding explanation for events formerly thought inexplicable.

Pegasus notes
During the 2130 check, the pressure in the lounge diner kitchen hall was normal atmospheric pressure, with a constant through draught coming in window and out kitchen vent.
Same during the first part of the 2200 check.
But there is a big change of scenario when the 2200 checker moves the door to almost closed, because this enables the through draught to slam the door shut.
Now suddenly the pressure in lounge diner kitchen hall drops from normal to negative because no air can enter apartment to replace air being sucked strongly up vent.
And then when the 2200 checker reopens the bedroom door, there is a single extra strong blast of air in through the window to bring the negative pressure in lounge etc back up to normal.
It was that one off blast of air which blew the curtains in.   
So that explains the difference between the 2130 check and the 2200 check.  http://miscarriageofjustice.co/index.php?PHPSESSID=dv5rq14n4fuh4s4mqau9lsmue5&topic=5477.msg197144#msg197144

[sadie]

Sadie - I replied to the wrong post and not yours above. Don't be concerned if you've seen it and are worrying about what I'm getting up to - just me getting mixed up ;)

I learned about The Venturi Effects and Bernoulii Effects whilst doing The Hydraulics and Applied Thermodynamics module of my HNC Course in Mechanical Engineering.   It wasn't my strongest subject, but I understood it better than some of that module.   However it has been 65 years since I did it and I am sure that some can describe it better than I can with my dyslexia.   I remember the principles.

Now, I am wondering why Barrier didn't know about it.   I seem to remember him being science educated and scientifcally knowledgeable in posts a few years ago.   Have I got that right, Barrier?

[barrier]

I learned about The Venturi Effects and Bernoulii Effects whilst doing The Hydraulics and Applied Thermodynamics module of my HNC Course in Mechanical Engineering.   It wasn't my strongest subject, but I understood it better than some of that module.   However it has been 65 years since I did it and I am sure that some can describe it better than I can with my dyslexia.   I remember the principles.

Now, I am wondering why Barrier didn't know about it.   I seem to remember him being science educated and scientifcally knowledgeable in posts a few years ago.   Have I got that right, Barrier?

Air pressure at sea level is 14.7 PSI , thats basic schoolboy stuff or at least it use to be, of course the pressure in the flat would be normal, with a breeze /gust of wind out side creating pressure against the outside any door or window opened would allow the rush of outside air in, the path of least resistance .Doesn't take any special knowledge to know this.

[Brietta]

I learned about The Venturi Effects and Bernoulii Effects whilst doing The Hydraulics and Applied Thermodynamics module of my HNC Course in Mechanical Engineering.   It wasn't my strongest subject, but I understood it better than some of that module.   However it has been 65 years since I did it and I am sure that some can describe it better than I can with my dyslexia.   I remember the principles.

Now, I am wondering why Barrier didn't know about it.   I seem to remember him being science educated and scientifcally knowledgeable in posts a few years ago.   Have I got that right, Barrier?

Seems to me that for anyone with a scientific background there is no mystery associated with understanding the Venturi effect as it appears to be elementary.

Yet his disbelief of Kate's testimony and description of it it is one of the cornerstones of Amaral's vendetta against the McCanns

[sadie]

Seems to me that for anyone with a scientific background there is no mystery associated with understanding the Venturi effect as it appears to be elementary.

Yet his disbelief of Kate's testimony and description of it it is one of the cornerstones of Amaral's vendetta against the McCanns

Maybe some can remember the old metal draw plates that were used when starting a fire in the grate.

The draw plate was almost the size of the fireplace aperture.  My Mum used to light a tiny fire in screwed up newspaper with a little kindling wood on top and an addment or so of tiny coal pieces.  The minute she got t lit, the draw plate was put across the aperute (with IIRC a tiny gap at the bottom).  A large piece of newspaper was slapped across the draw plate overlapping the aperture sides so sealing the gap.

There would be a sudden roar as the venturi effect took place and voila the fire was going. Sometimes the large sheet of newspaper went up in flames too and Mum just rapidly and calmly put it out by smothering it.  Quita a sight to see your Mum enveloped in flames!

I think the older generation were braver than we are with fire.   Grandpa used to smoke a pipe and used folded newspaper as spills which he lit from the open fire.   In old age, he had a huge beard and moustache which he regularly set  alight.   No panick , just smother the flames of spill and beard and moustache with your hand  and in his eighties his hands were shaky too.

[Myster]

Maybe some can remember the old metal draw plates that were used when starting a fire in the grate.

The draw plate was almost the size of the fireplace aperture.  My Mum used to light a tiny fire in screwed up newspaper with a little kindling wood on top and an addment or so of tiny coal pieces.  The minute she got t lit, the draw plate was put across the aperute (with IIRC a tiny gap at the bottom).  A large piece of newspaper was slapped across the draw plate overlapping the aperture sides so sealing the gap.

There would be a sudden roar as the venturi effect took place and voila the fire was going. Sometimes the large sheet of newspaper went up in flames too and Mum just rapidly and calmly put it out by smothering it.  Quita a sight to see your Mum enveloped in flames!

I think the older generation were braver than we are with fire.   Grandpa used to smoke a pipe and used folded newspaper as spills which he lit from the open fire.   In old age, he had a huge beard and moustache which he regularly set  alight.   No panick , just smother the flames of spill and beard and moustache with your hand  and in his eighties his hands were shaky too.

Ah yes, I remember it well...  https://youtu.be/vCMEPFSkQOw?t=1209

[sadie]

Ah yes, I remember it well...  https://youtu.be/vCMEPFSkQOw?t=1209

Thanks for that, Ret.

But no draw plate there, so no/little Venturi effect..  Crazy to do without one and it wouldn't work either, would it.  But it made good filming.

[G-Unit]

Maybe some can remember the old metal draw plates that were used when starting a fire in the grate.

The draw plate was almost the size of the fireplace aperture.  My Mum used to light a tiny fire in screwed up newspaper with a little kindling wood on top and an addment or so of tiny coal pieces.  The minute she got t lit, the draw plate was put across the aperute (with IIRC a tiny gap at the bottom).  A large piece of newspaper was slapped across the draw plate overlapping the aperture sides so sealing the gap.

There would be a sudden roar as the venturi effect took place and voila the fire was going. Sometimes the large sheet of newspaper went up in flames too and Mum just rapidly an
d calmly put it out by smothering it.  Quita a sight to see your Mum enveloped in flames!

I think the older generation were braver than we are with fire.   Grandpa used to smoke a pipe and used folded newspaper as spills which he lit from the open fire.   In old age, he had a huge beard and moustache which he regularly set  alight.   No panick , just smother the flames of spill and beard and moustache with your hand  and in his eighties his hands were shaky too.

I remember it well. My father-in-law used to stand the coal shovel upright and put the newspaper up against it. Then the constriction which was already present in the chimney was enhanced. Fireplaces fitted with dampers helped to increase the effect also, but rarely matched the 'newspaper effect' when lighting it.
https://www.mrfixitbali.com/building-design/chimneys-and-flues-43.html

[barrier]

Maybe some can remember the old metal draw plates that were used when starting a fire in the grate.

The draw plate was almost the size of the fireplace aperture.  My Mum used to light a tiny fire in screwed up newspaper with a little kindling wood on top and an addment or so of tiny coal pieces.  The minute she got t lit, the draw plate was put across the aperute (with IIRC a tiny gap at the bottom).  A large piece of newspaper was slapped across the draw plate overlapping the aperture sides so sealing the gap.

There would be a sudden roar as the venturi effect took place and voila the fire was going. Sometimes the large sheet of newspaper went up in flames too and Mum just rapidly and calmly put it out by smothering it.  Quita a sight to see your Mum enveloped in flames!

I think the older generation were braver than we are with fire.   Grandpa used to smoke a pipe and used folded newspaper as spills which he lit from the open fire.   In old age, he had a huge beard and moustache which he regularly set  alight.   No panick , just smother the flames of spill and beard and moustache with your hand  and in his eighties his hands were shaky too.

Those were the days, the door to the room had to left ajar so the fire could draw.