Definition and Validation of Cavitating Rocket Turbopump Transmission Matrices for Modular Multi Actuator Disk Approach

Cavitation induced instabilities are a critical issue to face in the design process of rocket turbopumps, and reduced-order linear methods still represent a powerful tool to evaluate their onset. The modular multi actuator disk approach is a successful method developed to study the dynamic behavior of compressors. Recently, it has also been proposed for the assessment of the dynamics of cavitating turbopumps. In this paper, the modular multi actuator disk approach was used as the mathematical framework to implement and validate a well-established model of a cavitating inducer developed in the 90s for the assessment of azimuthal instabilities with a particular focus on rotating cavitation. The matching between the obtained results and the available data in the open literature for a tapered inducer validated the dynamic model of the cavitating inducer implemented in the new mathematical framework. The flexibility introduced by the new modular approach represents a step toward the study of complex hydrodynamic systems that are not limited to the simplified configuration studied by the actuator disk model proposed in the 90s.

Vortex Ring Theory—An Alternative to the Existing Actuator Disk and Rotating Annular Stream Tube Theories

Currently, the actuator disk theory (ADT) and the rotating annular stream-tube theory (RAST), both of which predicate on the axial momentum and generalized momentum theories, among others, are commonly used in investigating the aerodynamic characteristics of horizontal axis wind turbines (HAWTs). These theories, which are based on a rotor with an infinite number of blades, typically do not properly capture the flow physics of wind blowing past the rotors of HAWTs. A vortex ring theory (VRT) that analyzes HAWTs based solely on the characteristics of fluids flowing past obstructions is proposed. The VRT is not predicated on the assertion that the induced velocity in the wake is twice the induced velocity at the rotor. On the contrary, it splits the axial induction factor in the wake into two components, namely, the induction or interference factor due to the solidity of the rotor and the induction factor due to the wake of the rotor aw; aw and its azimuthal counterpart are determined using the Biot–Savart law. The pressure differences across the rotor segments of a HAWT are derived from the Bernoulli equation for all the three theories. Blade segment/local areas based on the blade sectional geometry of the rotor are used in the case of the VRT to estimate the local forces. All the calculations in this study are based on the design parameters of the 5MW National Renewable Energy Laboratory’s reference offshore wind turbine. Pressure differences are plotted as functions of local radii using the calculated axial and azimuthal induction factors for each theory. The local power coefficient is plotted as a function of the local tip-speed ratio, while the local thrust coefficient is plotted as a function of the local radii for all the three theories. There is piece-wise agreement between the VRT, the ADT, the RAST and numerical and experimental data available in the literature.

Preliminary analysis of lip-wing concept using computational fluid dynamics and actuator disc theory

This thesis presents a preliminary analysis of the lip wing concept proposed by Dusan Stan of Aliptera Aircraft. A inviscid CFD-CAD actuator disk model was used to simulate a comparable geometry to that which was investigated experimental by Aliptera Aircraft. In general, a 10%-12% increase in thrust was produced at an optimal lip wing angle of 30o. This increase in thrust was consistent with the experimental results obtained by Aliptera Aircraft. These preliminary results are promising and encourage further research

Preliminary analysis of lip-wing concept using computational fluid dynamics and actuator disc theory

This thesis presents a preliminary analysis of the lip wing concept proposed by Dusan Stan of Aliptera Aircraft. A inviscid CFD-CAD actuator disk model was used to simulate a comparable geometry to that which was investigated experimental by Aliptera Aircraft. In general, a 10%-12% increase in thrust was produced at an optimal lip wing angle of 30o. This increase in thrust was consistent with the experimental results obtained by Aliptera Aircraft. These preliminary results are promising and encourage further research