Efficient Computation of "Stiff" Chemically Reacting Flow in Turbulent Free Jets

The chemically reacting flow in axisymmetric, turbulent free jets is solved numerically by a second-order accurate finite-difference scheme that is unconditionally stable with respect to the chemical rates. The transport properties are obtained from the turbulent kinetic energy model of turbulence. The momentum, energy, and turbulence model equations are solved by an explicit differencing scheme, whereas a hybrid expolcit/implicit scheme is used to solve the species conservation equations. High computational efficiency is attained by solving the equations in a natural coordinate system, and by employing the chemical element conservation principles to minimize the order of the matrix inverted to obtain the species concentrations. The scheme computes reacting jet flows in one-fifth the computer time required by any previously reported scheme.