# Talk:Convection–diffusion equation

## Given general equation not general

The general equation, as given on the page, is not very general, as it does not apply to cases with non-constant pressure or fluid density. Sampo Smolander (talk) 21:38, 27 March 2013 (UTC)

That's not exactly true: as for pressure (you consider fluid flow, I guess), ${\displaystyle R}$ is simply ${\displaystyle \nabla p}$, while the actual quantity being transported is the momentum, namely${\displaystyle \rho v}$ ( but that's N-S equations or Euler or something else in any case). The only missing feature is the possible dependence of the reaction term on the variable, namely ${\displaystyle R}$ should be indicated as ${\displaystyle R(c)}$. Dvd7587 (talk) 13:32, 8 June 2013 (UTC)

No no. Solubility of a gas in a liquid depends on pressure, so in the presence of a pressure gradient (a water column in a lake, for example, hydrostatic pressure) you cannot just take the derivative of concentration to see to which direction diffusion is supposed to go. Sampo Smolander (talk) 06:56, 29 August 2015 (UTC)

The general equation is always a start point for numerical solution. However, it is more useful to develop the equation in some other condition for better engineering application.GraceChen117 (talk) 20:51, 26 April 2017 (UTC)

## Index Notation

Having these equations written in index notation as well as having the vector notation would be helpful. Many times when you see the advection-diffusion equation it is written in index notation. Conor murphy (talk) 19:53, 26 April 2017 (UTC)

## Merge with Smoluchowski equation and Generic scalar transport equation

All of these articles are about the the same equation [albeit slightly different terminology and notation]. OK to merge? --Steve (talk) 13:52, 18 April 2012 (UTC)

Perhaps merge Convection–diffusion equation + Smoluchowski equation, but leave Generic scalar transport equation alone, since the first two are more physical, the third is more mathematical...
Also the first two are more closley about diffusion, but the general transport equation is about transport in general. 15:16, 18 April 2012 (UTC)
On second thought forget that - just merge them. 15:21, 18 April 2012 (UTC)

Done --Steve (talk) 20:01, 20 April 2012 (UTC)

Nice work - I hadn't notice till now. 15:27, 21 April 2012 (UTC)