# Damkohler number

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 Revision as of 17:35, 17 November 2005 (view source)Salva (Talk | contribs)← Older edit Latest revision as of 13:50, 6 February 2012 (view source)Peter (Talk | contribs) m (Reverted edits by Yan King (talk) to last revision by DavidF) (3 intermediate revisions not shown) Line 15: Line 15: This regime is the "well-stirred reactor", where products and reactants are rapidly mixed. This regime is the "well-stirred reactor", where products and reactants are rapidly mixed. The [[Karlovitz number]]  is linked to the Damkholer number. The [[Karlovitz number]]  is linked to the Damkholer number. + + + The Damkohler number is also defined in a chemical non-equilibrium process at very high velocities of the fluid or vehicles (with reference to fluid). There are two ratios of Damkohler number that can be defined and are as follows: + + 1. First Damkohler Number or DAM 1 + + $+ DAM 1 = \frac{t_{res}}{\tau} +$ + + Where $t_{res}$ is the residence time of the flow, where $\frac{L_{ref}}{U_{ref}}$ where $L_{ref}$ is the reference length of the vehicle and $U_{ref}$ is the reference velocity of fluid or vehicle with respect to fluid + + + 2. Second Damkohler Number or DAM 2 + + $+ DAM 2 = \frac{q_{ne}}{h_o} +$ + + Where $q_{ne}$ is the energy involved in a non-equilibrium process and $h_o$ is the total enthalpy of the flow [[Category:Dimensionless parameters]] [[Category:Dimensionless parameters]]

## Latest revision as of 13:50, 6 February 2012

The Damkohler number is used in turbulent combustion and corresponds to the ratio of chemical time scale $\tau_c$ and turbulent time scale $\tau_t$. This turbulent scale is usually taken as the integral scale.

$Da \equiv \frac{\tau_t}{\tau_c}$

Damkohler number measures how important is the interaction between chemistry and turbulence. Most combustion models are placed in the extremes of Damkohler.

If $Da << 1$ the turbulence is much faster than the chemistry. This regime is the "well-stirred reactor", where products and reactants are rapidly mixed. The Karlovitz number is linked to the Damkholer number.

The Damkohler number is also defined in a chemical non-equilibrium process at very high velocities of the fluid or vehicles (with reference to fluid). There are two ratios of Damkohler number that can be defined and are as follows:

1. First Damkohler Number or DAM 1

$DAM 1 = \frac{t_{res}}{\tau}$

Where $t_{res}$ is the residence time of the flow, where $\frac{L_{ref}}{U_{ref}}$ where $L_{ref}$ is the reference length of the vehicle and $U_{ref}$ is the reference velocity of fluid or vehicle with respect to fluid

2. Second Damkohler Number or DAM 2

$DAM 2 = \frac{q_{ne}}{h_o}$

Where $q_{ne}$ is the energy involved in a non-equilibrium process and $h_o$ is the total enthalpy of the flow