Water hammer principles in gaseous flow 1

[BillyShope]

I was an engineer at Chrysler in the fifties. (Yes, I'm that old.) At that time, it was quite easy to talk with other engineers about dynamic compressibility effects in gaseous flow. In other words, we realized that the sonic wave nonsense in Phillips' book simply could never explain the dyno numbers we were seeing. So, we soon realized that all we learned in school about water hammer had to be applied to that OTHER fluid: A gas! When we started applying the water hammer equations to the gas in a tuned intake manifold, the pressures all began to make sense!

One easily recognized example was the first club car assembled by the Ramchargers. The intake manifold was taken right from a dyno room. The eight exhaust pipes ended with cones for the obvious purpose of reducing energy loss during reverse flow.

So, the obvious question is: Why are the water hammer effects apparently ignored today when it comes to the design of intake manifolds?

 

[enginesrus]

Billy, welcome to this site. I have much respect for the old timer engineers, you guys came up with the ideas that are now in computers for the so called engineers of today. I have a Friden.

Here is your article.

https://www.hotrod.com/articles/hrdp-9907-ram-tuning-guide/

 

[VEBill]

More properly, incorporated...?

Arguably no. 'Superseded' (assuming that I spell it correctly) is arguably a better word choice than 'incorporated".

In this example, Water Hammer effects should arise naturally as an emergent effect in any sufficiently accurate model.

Like murmuration (flocking) with birds, the larger scale effect should arise naturally. 'Emergent Effects' has been a hot topic in recent years, in many fields. It even made it to the PBS 'Nova' science series as an episode.

(Ref. PBS Nova 'Emergence'- How does the "intelligence" of an ant colony or the stock market arise out of the simple actions of its members?)

'Incorporated' implies that somebody needed to explicitly embody this effect into their CFD physics engine, as if physics needs a patch. If so, then arguably their physics engine wasn't finished.

It's a good test of any computer model; to check it to ensure that expected emergent effects naturally arise (given suitable conditions). If they don't, then the physics engine and/or model isn't finished.

One wouldn't say that Einstein 'incorporated' Newtonian physics into his theories. His theories arguably 'superseded' Newtonian physics.

The word 'incorporated' doesn't quite precisely convey how the emergent effects, or previous theories, naturally appear in the better models.

Sorry for the semantics, but this is one of my favorite concepts.

 

[inline6]

i agree with Brian. if you vary length of the induction you commonly find that the closed pipe harmonics are not what makes the best VE. the length that produces the best cylinder filling during BDC to IVC give or take a bit is king, the so called ramming process. this is evident in 1D simulations to. a proper exhaust does a good enough job of flushing the system during overlap, so while a bit of help from the inlet side wouldnt hurt it turns out you lose out from somthing else