Canted Nozzles Research Articles

Numerical Simulations of Canted Nozzle and Scarfed Nozzle Flow Fields

Computational fluid dynamics (CFD) techniques are used for the analysis of issues concerning non-conventional (canted and scarfed) nozzle flow fields. Numerical simulations are carried out for the quality of flow in terms of axisymmetric nature at the inlet of canted nozzles of a rocket motor. Two different nozzle geometries are examined. The analysis of these simulation results shows that the flow field at the entry of the nozzles is non axisymmetric at the start of the motor. With time this asymmetry diminishes, also the flow becomes symmetric before the nozzle throat, indicating no misalignment of thrust vector with the nozzle axis. The qualitative flow fields at the inlet of the nozzles are used in selecting the geometry with lesser flow asymmetry. Further CFD methodology is used to analyse flow field of a scarfed nozzle for the evaluation of thrust developed and its direction. This work demonstrates the capability of the CFD based methods for the nozzle analysis problems which were earlier solved only approximately by making simplifying assumptions and semi empirical methods.

Effects of Shear-Layer Reattachment on the Nozzles of a Launch Vehicle

Wind-tunnel tests in the Mach number range of showed the reattachment of shear layer from the strap-on boosters onto a point on the canted nozzles of a multibooster launch vehicle model. Such a reattachment can cause dynamic side loads on the nozzles and the associated gimbal actuators. A mean flow model of the forcing function was construed based on qualitative studies. The forcing function associated with the external excitation up to 550 Hz was quantified using specially designed strain-gauged nozzles that had a natural frequency of more than 700 Hz. With gimbaling, magnitudes of mean moments at the simulated location of the gimbal actuator were found to increase while the fluctuations decreased. Simple passive “load alleviation devices,” which prevent local flow separation, deflect the trajectory of the separating shear layer and avoid reattachment on the nozzle were found to substantially reduce the flow-induced mean moments. A short semicircular segment that envelopes the boat tail of the strap-on boosters was found to be the most effective device for reducing the mean moments, as well as flow-induced unsteadiness on the nozzles at the location of gimbal actuators. The nozzle response indicates occurrence of discrete frequencies of about 103 and 466 Hz in the forcing function.

An assessment of thrust vector concepts for twin-engine airplane

Thrust vector nozzles are finding place on modern fighter airplanes because of the benefits they provide and also due to diminishing weight penalty of such nozzles. They offer additional benefits in the case of a twin-engine airplane. Different vectoring configurations such as multi-axis vectoring, single-axis pitch vectoring and single-axis vectoring with canted nozzles have been studied with respect to twin-engine airplane configuration. Modeling and integration of thrust vector nozzles with rigid airplane six-degrees-of-freedom equations of motion have been carried out in this article. Using the integrated model, a comparative study is carried out to summarize the capabilities and limitations of various nozzle configurations with respect to performance of an airplane in velocity vector roll and in Herbst maneuvers. The airplane model used in this work is the F-18/HARV and all simulation results have been produced using a nonlinear dynamic inversion controller developed in Matlab/Simulink environment. Results show that a multi-axis thrust vectoring provides additional benefits as compared to single-axis vectoring with canted nozzles in high angle of attack velocity vector roll and in Herbst maneuvers. The single-axis pitch only vectoring has roll control power and lacks in yaw control power, to execute the velocity vector roll maneuver.

Three-dimensional, two-phase, transonic, canted nozzle flows

A time-dependent numerical scheme, in conjunction with a three-dimensional, body-fitted, coordinate transformation technique, is utilized for the solution of subsonic-transonic-supersonic flows-both gas-only, one-phase, and fully coupled, gas-particle, two-phase-inside three-dimensional canted nozzles of arbitrary configurations. No difficulty is encountered with the time-dependent formulation for the solution of mixed transonic flowfield, which has been a bottleneck in many three-dimensional nozzle flow studies