For one-point control, the oxidizer boundary condition is relaxed and temperature at some internal point is specified. As a result, the H equation is modified, as shown in Equation 14–23 .

(14–23)

It can be noted that the above treatment is similar to the one used for fixing temperature at a point employed in the Flame-speed Calculator (Boundary Conditions ). The H information then propagates from the fixed point to either inlet. At the oxidizer boundary the mass flux term (ρ _o U _o) appears as boundary value F _o in the Y _k equations, instead of as a condition for the H equation.

In addition, it is also possible to introduce some condition on the fuel inlet velocity, such as U _f = g(U _o ). This is useful in matching experimental conditions such as equal velocities or momentum of the jets. In such cases, another boundary condition must be relaxed and the natural choice is the fuel (or oxidizer) velocity boundary condition. The Flame-Extinction Simulator model adds an extra equation for U _f. This equation merely copies U _F at each grid point as is done for the pressure eigenvalue. At the oxidizer boundary, the F _o condition is imposed on the equation for U _f using U _f = g(U _o ). Thus,

(14–24)

The species conservation equations are then recast to use the oxidizer mass flux in terms of U _f at the oxidizer boundary.

If the fuel velocity is fixed and the fixed temperature value is chosen on the fuel side of the flame then a decrease in the fixed temperature results in a decrease in the global strain rate, whereas if fixed temperature is chosen on the oxidizer side then a decrease in the fixed temperature results in an increase in the strain rate (for the upper branch solutions).