CFD Online Discussion Forums (https://www.cfd-online.com/Forums/)
-   Siemens (https://www.cfd-online.com/Forums/siemens/)
-   -   tutorial error? (https://www.cfd-online.com/Forums/siemens/52388-tutorial-error.html)

 K.L.Huang April 28, 2000 08:09

tutorial error?

in the tut2.2 air inlet v=10m/s

A=0.0254m *0.0254m

Q=6.4516e-3 m3

solid particle

q=0.01% * Q =6.4516 e-7 m3/s

diameter =4e-5 m

volume =3.35103e-14 m3

that is, particle number 19,252,575.58 per second

but in the tutorial 2.2 write 1,925,257.56 per second

I think there must be something wrong? anybody can tell me?

K.L.Huang

 John C. Chien April 29, 2000 09:27

Re: tutorial error?

(1). I can only say that both numbers were not computed by the computer. It is more likely that those are calculated by hand using electronic calculators. (2). Why not write a simple Fortran program and check the result again. What do you mean by .58 particle number per second? How do you count it?

 K.L.Huang April 29, 2000 11:33

Re: tutorial error?

i dont mean the .56 or .58 i mean that the particle flow rate should 10 times the number mentioned in the tut book.

 John C. Chien April 29, 2000 21:16

Re: tutorial error?

(1). Q=6.4516E-07 (2). volume=3.35103E-14 (3).Q/volume=(6.4516/3.35103)E+07=1.925258801E+07=19252588.01 (4). If Q/volume=19252575.58, and Q=6.4516E-07, then volume=(6.4516E-07)/(19252575.58)=(6.4516/1.925257558)E-14=3.351032164E-14 (5). If volume=(4/3)pi(rxrxr)=(4/3)pi(2x2x2)E-15=(32pi/3)E-15=33.51032164E-15 (6). Which means, if we use the volume stated in the message, Q/volume should be 19252588.01. And both Q/volume numbers quoted in the message are incorrect.(these are 19252575.58 and 1925257.56) (7). Since my volume of the particle is 33.51032164E-15 which is different from the stated volume of 3.35103E-14, one can only say that the stated volume is incorrect. (8). Now we have shown that the volume, the two Q/volume numbers are all incorrect. (9). The correct Q/volume is 1.925257558E+07, but only if the correct volume of 33.51032164E-15 is used. (10). So much for the simple math.

 K.L.Huang May 1, 2000 12:49

Re: tutorial error?

(1). Q=6.4516E-07 (2). Volume=3.35103E-14 (3). Q/volume=(6.4516/3.35103)E+07

=1.925258801E+07

=19252588.01 (4). If Q/volume=19252575.58, and Q=6.4516E-07,

then volume=(6.4516E-07)/(19252575.58)

=(6.4516/1.925257558)E-14

=3.351032164E-14 (5). If volume=(4/3)pi(rxrxr)

=(4/3)pi(2x2x2)E-15

=(32pi/3)E-15=33.51032164E-15 (6). Which means, if we use the volume stated in the message,

Q/volume should be 19252588.01.

And both Q/volume numbers quoted in the message are incorrect.

(these are 19252575.58 and 1925257.56) (7). Since my volume of the particle is 33.51032164E-15

which is different from the stated volume of 3.35103E-14,

one can only say that the stated volume is incorrect. (8). Now we have shown that the volume,

the two Q/volume numbers are all incorrect. (9). The correct Q/volume is 1.925257558E+07,

but only if the correct volume of 33.51032164E-15 is used. (10).So much for the simple math.

-------------------------------------------------------------------------------- Mr.Chien

Thanks very much for your detail calculation of my question. But I think you really mis-understand my original question. To me , it is a physical problem, not a math or numerical problem. I think Q/volume=19252588.01 (item3)

=19252575.58 (item4)

=19252588.01 (item5 first one)

=19252575.58 (item5 second one) But not equal to 1925257.56 (item5 one and the tut2.2 one) Do'nt you notice that there is a difference of one order(10^1). This makes the calculated particle flow rate in the modle is only 1/10 of real flow rate. Understand? I agree with your opnion in item 10, "So much for the simple math". But it is physical not a math problem.

 John C. Chien May 1, 2000 13:20

Re: tutorial error?

(1). I think I understand your question. (2). I just don't want to say that your number is less incorrect than their numbers. (3). It is quite obvious that the decimal point is misplaced. So, their number is incorrect by a factor of ten.

 All times are GMT -4. The time now is 14:20.