[medaouarwalid]

hello every one , a was reading a publication from a fluid dynamics journal , the topic was talking about comparing the effect of the number of jets in mixing air in a room. the autor compared a configuration of 1 jet with an other configuration of 5 jets for the same momentum flux at the exit, this is logical. but how did he calculate that momentum flux ?? for example he found the momentum flux for the configuration of 1 jet = 1.85 kg*m/s the only formula that i found to give that result is density*v*Area*v which is mass flow rate times the velocity . if the autor used that formula the unit must be kg*m/s² and not kg*m/s, also if he used that formula how did he get 1.85 for the configuration of 5 jets, because even if we do density*v*Area*v * 5 we will not get that result. any explications please !!!

[FMDenaro]

Definition of flux of the momentum is quite general as it is sum of the convective (rho vv), diffusive (2mu S) and pressure (Ip) fluxes.

[medaouarwalid]

Originally Posted by FMDenaro

Definition of flux of the momentum is quite general as it is sum of the convective (rho vv), diffusive (2mu S) and pressure (Ip) fluxes.

hi, thank you for replying me each time i put a question , i apreciate this. can you please explain to me how to apply this definition on the example sited above to get the same result as the author , convective flux is rho v v = 1.2*35*35 . diffusive flux is 2muS = 2*0.0000178*0.001256 . the third flux i dont know how to calculate it , there is no pression given in the topic

[FMDenaro]

I don't know what he means for"Effective"... I see from the dimension that it expresses m*v that is not the momentum flux...

[medaouarwalid]

Originally Posted by FMDenaro

I don't know what he means for"Effective"... I see from the dimension that it expresses m*v that is not the momentum flux...

Effective i think is because of the effective diameter of the nozzle, because the complexity of the shape at the exit they use effective diameter. What is m ? And Could a published topic contain wrong things ?

[FMDenaro]

Originally Posted by medaouarwalid

Effective i think is because of the effective diameter of the nozzle, because the complexity of the shape at the exit they use effective diameter. What is m ? And Could a published topic contrain wrong things ?

m is a mass=density*volume expressed in Kg

[medaouarwalid]

Originally Posted by FMDenaro

m is a mass=density*volume expressed in Kg

there is no length of the nozzle mentionned to calculate the volume, it should be 35 m to get that result and this is illogical , those nozzles are about 0.009 m of length. I even wrote to the author but he didnt reply to me