# 03-04-2024 - Physics - Fundamentals of thermodynamics (13/13)[EN]-[IT]

~~~ La versione in italiano inizia subito dopo la versione in inglese ~~~

ENGLISH
03-04-2024 - Physics - Fundamentals of thermodynamics (13/13)[EN]-[IT]

Forced convection in external and internal flows
Boundary layer
By boundary layer we mean the thickness adjacent to the surface within which the temperature between Tw and Tf,∞ (would be the temperature in the disturbed area)

Below is a diagram to better understand what the boundary layer is

Laminar motion and turbulent motion
Difference
Turbulent motion is synonymous with unstable equilibrium (stronger frictional forces), laminar motion is synonymous with stable equilibrium, in which disturbances tend to be absorbed.

Schemes
Laminar motion

Turbulent motion

Natural convection
Difference with forced convection
In natural convection the speed range depends on the temperature.
In other words, in natural convection the motion is triggered by differences in density, which are in turn linked to differences in temperature. Thermal energy transfer occurs naturally without the aid of work.

Momentum equation
The expansion coefficient
The expansion coefficient represents the percentage change in density for a change in temperature (it has a dimension equal to the inverse of a temperature)

Energy equation
Natural convection
Below the energy equation in the case of natural convection is as follows.

What is it
The purpose of dimensionlessness is to simplify an equation in n variables and m dimensions into an equation with dimensionless variables. This allows you to create more understandable and less long equations and formulas.

Grashof number
Below is the Grashof number formula

Conclusions
In turbulent motion the fluid moves in a disorderly manner, whereas in laminar motion the trajectories are straight and the velocity profile is parabolic (see sketches above)

Request
Have you ever carried out studies on turbulent motion or laminar motion?

03-04-2024 - Fisica - Fondamenti di termodinamica (13/13)[EN]-[IT]

La convezione forzata nei flussi esterni ed interni
Strato limite
Per strato limite si intende lo spessore adiacente alla superficie all'interno della quale la temperatura compresa tra Tw e Tf,∞ (sarebbe la temperatura in zona disturbata)

qui di seguito uno schema per comprendere meglio cosa è lo strato limite

Moto laminare e moto turbolento
Differenza
Il moto turbolento è sinonimo di equilibrio instabile (sforzi di attrito più forti), il moto laminare è sinonimo di equilibrio stabile, in cui i disturbi tendono ad essere assorbiti.

Schemi
Moto laminare

Moto turbolento

Convezione naturale
Differenza con convezione forzata
Nella convezione naturale il campo delle velocità dipende dalla temperatura.
In altre parole nella convezione naturale il moto è innescato da differenze di densità, legate a loro volta a differenze di temperatura. Il trasferimento di energia termica avviene in maniera naturale senza l'ausilio di lavoro.

Equazione della quantità di moto
Il coefficiente di espansione
Il coefficiente di espansione rappresenta la variazione percentuale di densità per una variazione di temperatura (ha dimensione pari all'inverso di una temperatura)

Equazione dell’energia
Convezione naturale
Qui di seguito l'equazione dell'energia nel caso di convezione naturale è la seguente.

Cosa è
Lo scopo dell'adimensionalizzazione è quello di semplificare un'equazione in n variabili e m dimensioni in un'equazione con variabili adimensionali. Questo permette di creare equazioni e formule più comprensibili e meno lunghe.

Numero di Grashof
Qui di seguito la formula del numero di Grashof

Conclusioni
Nel moto turbolento il fluido si muove in maniera disordinata, nel moto laminare invece le traiettorie sono rettilinee ed il profilo di velocità parabolico (vedi schizzi riportati sopra)

Domanda
Avete mai effettuato studi sul moto turbolento o sul moto laminare?

THE END

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Hello @stefano.massari
You have been losing all curation rewards by upvoting comments from the accounts "biyimi" & "precab" as we remove all the rewards from these upvotes.

The account belongs to a well-known scammer (identity thief, plagiarist, spammer, etc).

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Thanks for reporting unwanted accounts to me. It seemed to me that they were interested in my posts, they commented often. I will no longer follow them or comment on them.

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Thanks a lot !

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This is not true. I have myself clear over and over again in their discord server that we are not the same person.
We are different people. Biyimi just happened to introduce me to this platform. You can read through my introduction post to confirm that.

I am been accused for what I didn't do and I have made it clear to them in their discord server but they will not listen.

I dropped quality post, they didn't talk about that also?

And I have also made myself clear that it is not what they are thinking by me those list of recommended users. Of course there are other people I comments on that didn't upvotes me but I still comments on.

What else do you think I should do.

I am innocent of all this false accusations.

My reputation on this platform is at stake because of this false accusations

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Hi @hivewatchers, @precab 's comments on my physics-related articles seemed interesting to me, can you check if he/she is really a spamming user?

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(Edited)

They claim that they diligently and in detail read at least 50 posts per day. Apparently some 50 comments within just 1 hour.
A few times I asked them to stop commenting on that list and engage with thousands of other Hiveians instead of hitting this list of accounts. They have been refusing and continued to keep hitting these lucrative accounts.
"biyimi" likely created an account "precab" and it seems that he was posting on it for a few weeks until a "friend" started using it and posted an introduction post. The way both accounts comment, and the manner both are speaking in Discord and on chain suggests that it is the same person. Although it seems that a "friend" may occasionally pop in to say something.

By the way, this is the history of "biyimi" (aka "mandate" in older account - new account "biyimi" was created to circumvent blacklist on old account) history of abuse:

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(Edited)

I'd say I have nothing else to add. A very broad analysis. I figured out how to remember a user who was reported, I muted him and then I won't follow him anymore. @hivewatcher Good job

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The drawing of that turbulent motion seem easy and will be very easy to remember

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