1. finite volume predictor-corrector explicit method based on a Mac Cormack scheme with second and fourth order numerical damping 17. In the frame of the present study, a detailed description of this method is not possible, but this will be one of the main objectives of a future paper. The results presented hereafter have been obtained under the following computational conditions : 1) the computational domain for the half-height total duct including expansion area consists of a 101 x 17 grid in x and y directions, respectively, with strong refinement in the throat region, 2) the initial solution for the computational run is the choked one-dimensional solution, and 3) the twodimensional solution is assumed to have attained the asymptotic steady-state after 9000 time steps i.e. for an actual time of 4.2 x 10-3 s.
2. $ .E13 >._8._8-95-+
3. and twodimensional descriptions is obtained in the exit section, and 2) the flow is more aocelerated in the center area than near the wall but the Mach number average value is not truly different from the one-dimensional value in the exit section. Therefore, the small influence of two-dimensional flow effects on instantaneous nozzleless motor performance predicted by King 10 for actual operating conditions (head-end pressure range 60-100 atm., matched expansion to 1 atm., realistic values for y, Ts, MW,) is also demonstrated in the present cold-flow simulation Study. Although King disregarded all transverse static pressure gradients in the expansion area, he found a twodimensional effect improvement on thrust or specific impulse relative to the one-dimensional analysis of about 0.5 to 0.6 percent (y = 1.3, Ts = 3000 K, zero burnrate exponent), when the present study results in a 0.4 peroent improvement. This good agreement reinforces the fact that whatever are the motor operating conditions, the direct two-dimensional flow influence on instantaneous nozzleless performance is probably a second-order effect. However,