Venturi effect air flow in buildings

I'm thinking thoughts that I'm not sure are correct, or what the implications are.

The venturi effect says that a fluid's velocity increases as it goes though a constriction, and the pressure on the other side decreases.  

Venturi effect

In buildings the effect can be a problem,

venturi page on wikipedia wrote:Large cities where wind is forced between buildings - the gap between the Twin Towers of the original World Trade Center was an extreme example of the phenomenon, which made the ground level plaza notoriously windswept.[7] In fact, some gusts were so high that pedestrian travel had to be aided by ropes.[8]

Or it can be useful

venturi page on wikipedia wrote: Hawa Mahal of Jaipur, also utilizes the Venturi effect, by allowing cool air to pass through, thus making the whole area more pleasant during the high temperatures in summer.

Looking at that beautiful building  Hawa Mahal


That pic is the back side, on the front, the arches are much bigger, allowing air in


The effect of this construction was the air flowed through the rooms, keeping it cool.

So if I am understanding it right the venturi effect is happening as the air comes pushing in through the big arches, and it hits all the lattice windows on the back, and that increases the flow rate as it goes out, decreasing pressure on the exterior, so it pulls more air in, keeping a constant breeze.
Is my interpretation right?

If it is, that might be a neat way to keep low speed vertical wind turbines running smoothly. I knew you could use the air flow in gaps between buildings to amplify the wind speed, but if it could be spread across a wider area, it could run more turbines in a line. I'm thinking decorative fencing with vertical axis turbines at basically ground level for ease of maintenance.

My other thought is to make a summer deck cooling screen that pulls like that, to increase air flow across the deck.

Am I understanding this right? If so, any other neat ideas off the concept? The area I'm in has constant low wind, at least, with higher wind being common. I like the idea of very low scale wind power generation worked into decorative systems. I also like the idea of basically passive cooling that is decorative.

Good Morning Ms. Pearl;
I like your ideas around directing airflow to provide a cooling breeze on your deck.
Anything that help's with the heat and high humidity.

About wind power generation, I think that is a bigger can of worms than you want to dig into.
My understanding of micro wind power is it takes quite a bit of a breeze to even spin one up to generating speed.
They really need a steady strong wind to make worthwhile charging power...  plus the faster they turn, the louder they become.

Much easier to use high-voltage solar panels with an mppt charge control.
Solar systems are really hot shit these days compared to the vintage old-school system that I use.

I'm trying to go on with my day, but my head is changing the song by America "Ventura Highway" into "venturi breezeway in the sunshine..."

There are some venturi aided designs for renewable power on grid scale.

I think it was in Australia where they took plastic and draped it across a big open area, and then slowly rose the plastic up into a big funnel. At the apex of the funnel was a reversible wind turbine. As the sun heated up the earth, the heat rose and was channeled through the turbine making power. At night as the earth cooled it went backwards down through the turbine. If memory serves me right it was only a megawatt that it produced, however.

I work in hydropower, and we use the venturi effect to make 15 megawatts per hour, or 86,000 gigiwatts per year due to the venturi effect. At our dam, the penstocks are shaped in a venturi shape. At the apex of the venturi the turbines are situated. The water pressure of the dam (Head pond height versus tailrace depth) shoots out into the venturi throat of the penstock and spins the runners with greater force. These two penstocks turn (2) generators making 8 megawatts per hour. To take the most advantage of the venturi effect, we use Kaplan turbines that are 4 bladed propellers that have variable pitch. Since we can change the attack angle of the water striking the turbine, we can get greater control and efficiency. At start up, we get higher torque, but at full gate opening, we get less turbined water (less water being released out of the dam) for the same amount of power produced.

There are other renewable energy sources that use the venturi effect as well I am sure, as it is such a great principal of physics, one of the few times you really get something extra for nothing.

Just thought of another use of venturi structures making renewable power.

I have my high pressure steam license and so when I worked at a trash-to-energy plant where they take household and industrial garbage, shred it, and then burn it to make steam, that steam is channeled into a turbine that spins and makes electricity. At that facility, a small one granted, they make 31 megawatts of power per hour with two boilers.

The venturi effect comes from the steam after it makes power. It needs to be condensed, so it is run through cooling towers and these are venturi shaped. As the hot steam is shot into the cooling tower, the negative pressure forces it to speed up, where more air acts upon it, cools the steam to below 212 degrees, and it drops down to the cooling pond under it. There it is pumped back through the boiler where it will be reheated and the whole cycle starts again. Without the venturi shaped cooling tower (the iconic massive structures seem at most boilers no matter how they heat the water to steam) the steam would not condense so easily back to liquid water.

Pearl, study the use of wind towers in the Middle East.
I think I started a topic on it ages ago.

A lot of older southern houses had a cuppola that would suck out the warm air and pull in cooler air as the heated air was vented out. I was told that candles or lanterns multiplied the effect if they were above the first floor/ventilation windows. Shotgun house were narrow to allow for cross flow ventilation.

Robert Ray wrote:A lot of older southern houses had a cuppola that would suck out the warm air and pull in cooler air as the heated air was vented out. I was told that candles or lanterns multiplied the effect if they were above the first floor/ventilation windows. Shotgun house were narrow to allow for cross flow ventilation.

Here in Maine there was a lot of chicken barns built in the 1970's with the same principal. Long but narrow to allow the high ammonia of manure to be pulled out of the building.

My barn has an accidental venturi effect that help suck the manure smells for my sheep. Down low the sheep were protected from drafts, but over their heads was plenty of ventilation. It too was long and narrow, but situated East to West that made it draft as it did. It was all accidental.

Here's an article that hits all the high points of how the old Florida cracker houses were cooled:

https://www.theledger.com/story/news/2005/10/08/cracker-houses-are-reminders-of-life-before-air-conditioning/25908013007/

Not quite venturi effect but related.

Having a hard time locating the article, but Sandia Labs recently had a news item about their research on microturbines driven by airfoil (think plane wing) effect.  

The gist was -
   small fan/generator in a pipe
   pipe attached to airfoil with small ports at the apex of the "wing"
   air flows over the "wing" and pulls air out through the small ports
   air pulled though pipe causing fan to spin
Unlike normal wind turbines, these units would not be limited by excess wind speed. The small size allows them to function at much lower wind speeds as well.
Wish I had saved that link... Sorry, maybe someone else will have better luck searching.

I think this is how those soda bottle cooling systems work, yes?  You've got a board (wood or cardboard) with holes in.  You cut off the ends of soda or water bottles and pop those through the holes with the neck bit facing in.  The air comes into the larger end and gets squeezed down and accelerated through the neck, thus producing a wind tunnel effect as many times over as you've got bottles.  These boards get installed in a window and provide lovely cooling air to the room.  

I was wondering about it today, actually.  How best to keep the skeets out with this design without the effect of diffusing the air... ?

Nissa Gadbois wrote:I think this is how those soda bottle cooling systems work, yes?  You've got a board (wood or cardboard) with holes in.  You cut off the ends of soda or water bottles and pop those through the holes with the neck bit facing in.  The air comes into the larger end and gets squeezed down and accelerated through the neck, thus producing a wind tunnel effect as many times over as you've got bottles.  These boards get installed in a window and provide lovely cooling air to the room.  

I was wondering about it today, actually.  How best to keep the skeets out with this design without the effect of diffusing the air... ?

Yeah, pretty much :D
I'd put a screen on the outside, make a frame that sticks out past the bottles a bit, and put it on that.  It won't block a lot of air. If you want to not lose much air flow at all, make the frame about twice the size of the bottle area, and put a screen twice the size that fits the frame. That gives you air flow to make up for the amount you lose to the screen. Example, the bottles are 1 foot by 1 foot, make the frame 2 foot by 2 foot, and the screen. You'll need extra wood or cardboard to fill in between the bottles and the frame, as the air has to have no place to go but through the bottles.