Demonstration of a coupled floating offshore wind turbine analysis with high-fidelity methods

This paper presents results of numerical computations for floating off-shore wind turbines using, as an example, a machine of 10-MW rated power. The aerodynamic loads on the rotor are computed using the Helicopter Multi-Block flow solver developed at the University of Liverpool. The method solves the Navier–Stokes equations in integral form using the arbitrary Lagrangian–Eulerian formulation for time-dependent domains with moving boundaries. Hydrodynamic loads on the support platform are computed using the Smoothed Particle Hydrodynamics method, which is mesh-free and represents the water and floating structures by a set of discrete elements, referred to as particles. The motion of the floating offshore wind turbine is computed using a Multi-Body Dynamic Model of rigid bodies and frictionless joints. Mooring cables are modelled as a set of springs and dampers. All solvers were validated separately before coupling, and the results are presented in this paper. The importance of coupling is assessed and the loosely coupled algorithm used is described in detail alongside the obtained results

Parallel Evaluation of Quantum Algorithms for Computational Fluid Dynamics

The development and evaluation of quantum computing algorithms for computational fluid dynamics is described along with a detailed analysis of the parallel performance of a quantum computer simulator developed as part of the present work. The quantum computer simulator is used in the evaluation of the quantum algorithms on a conventional parallel computer, and is applied to quantum lattice-based algorithms as well as the Poisson equation. A key result is a demonstration of how the Poisson equation can be solved effeciently on a quantum computer, while its use within a larger algorithm representing a full CFD solver poses a number of signifi- cant challenges

Variable-speed tail rotors for helicopters with variable-speed main rotors

Variable tail rotor speed is investigated as a method for reducing tail rotor power, and improving helicopter performance. A helicopter model able to predict the main rotor and tail rotor powers is presented, and the flight test data of the UH-60A helicopter is used for validation. The predictions of the main and tail rotor powers are generally in good agreement with flight tests, which justifies the use of the present method in analyzing main and tail rotors. Reducing the main rotor speed can result in lower main rotor power at certain flight conditions. However, it increases the main rotor torque and the corresponding required tail rotor thrust to trim, which then decreases the yaw control margin of the tail rotor. In hover, the tail rotor may not be able to provide enough thrust to counter the main rotor torque, if it is slowed to follow the main rotor speed. The main rotor speed corresponding to the minimum main rotor power increases, if the change of tail rotor power in hover is considered. As a helicopter translated to cruise, the induced power decreases, and the profile power increases, with the profile power dominating the tail rotor. Reducing the tail rotor speed in cruise reduces the profile power to give a 37% reduction in total tail rotor power and a 1.4% reduction to total helicopter power. In high speed flight, varying the tail rotor speed is ineffective for power reduction. The power reduction obtained by the variable tail rotor speed is reduced for increased helicopter weight

Numerical Simulations on the PSP Rotor Using HMB3

This work presents CFD analyses of the isolated Pressure Sensitive Paint (PSP) model rotor blade in hover and forward flight using the structured multi-block CFD solver of Glasgow University. In hover, two blade-tip Mach numbers (0.585 and 0.65) were simulated for a range of blade pitch angles using fully-turbulent flow and the k-ω SST model. Results at blade-tip Mach number of 0.585 showed a fair agreement with experimental Figure of Merit and surface pressure coefficients obtained in the Rotor Test Cell (RTC) at NASA Langley Research Center. Comparisons are presented at blade-tip Mach number of 0.65 in terms of integral blade loads, surface pressure coefficients and position of the tip-vortex cores with published numerical data. Finally, the flow around the PSP rotor in forward flight was also computed at medium thrust (CT =0.006) and results were compared with published experimental data

Prediction of Helicopter Rotor Hover Performance using High Fidelity CFD Methods

No abstract available

Whirl and Stall Flutter Simulation Using CFD

This paper presents recent research on numerical methods for whirl and stall flutter using computational fluid dynamics. The method involves coupling of the HMB3 CFD solver of the University of Glasgow and a NASTRAN derived structural model. Based upon a literature survey, a significant amount of research has been conducted on the numerical investigation of tiltrotors, with a focus on the XV-15 and V-22 aircraft. Within this paper, the coupling procedure is presented along with a steady CFD computation to highlight the accuracy of the high-fidelity method. In addition to this, a simple method is used to investigate the whirl flutter boundary of a standard propeller and the XV-15 blade

Control synthesis for an unmanned helicopter with time-delay under uncertain external disturbances

This paper presents the controller synthesis for an unmanned helicopter with minimum initial information about the parameters of its mathematical model with time-delays of measured and control signals. The unknown parameters, wind disturbances, and system nonlinearity are considered as external disturbances that are estimated using a multi-gap observer. The estimates obtained are used in the control law to improve the stability rate for flight regimes

Unsteady loads for coaxial rotors in forward flight computed using a vortex particle method

Recent advances in coaxial rotor design have shown benefits of this configuration. Nevertheless, issues related to rotor-head drag, aerodynamic performance, wake interference, and vibration should also be considered. Simulating the unsteady aerodynamic loads for a coaxial rotor, including the aerodynamic interactions between rotors and rotor blades, is an essential part of analysing their vibration characteristics. In this article, an unsteady aerodynamic analysis based on a vortex particle method is presented. In this method, a reversed-flow model for the retreating side of the coaxial rotor is proposed based on an unsteady panel technique. To account for reversed flow, shedding a vortex from the leading edge is used rather than from the trailing edge. Moreover, vortex-blade aerodynamic interactions are accounted for. The model considers the unsteady pressure term induced on a blade by tip vortices of other blades, and thus accounts for the aerodynamic interaction between the rotors and its contribution to the unsteady airloads. Coupling the reversed-flow model and the vortex-blade aerodynamic interaction model with the viscous vortex-particle method is used to simulate the complex wake of the coaxial rotor. The unsteady aerodynamic loads on the X2 coaxial rotor are simulated in forward flight, and compared with the results of PRASADUM (Parallelized Rotorcraft Analysis for Simulation And Design, developed at the University of Maryland) and CFD/CSD computations with the OVERFLOW and the CREATE-AV Helios tools. The results of the present method agree with the results of the CFD/CSD method, and compare to it better than the PRASADUM solutions. Furthermore, the influence of the aerodynamic interaction between the coaxial rotors on the unsteady airloads, frequency, wake structure, induced flow, and force distributions are analysed. Additionally, the results are also compared against computations for a single-rotor case, simulated at similar conditions as the coaxial rotor. It is shown that the effect of tip vortex interaction plays a significant role in unsteady airloads of coaxial rotors at low speeds, while the rotor blade passing effect is obviously strengthened at high-speed

Understanding Transonic Weapon Bay Flows

No abstract available