Vortex lattice method

About: Vortex lattice method is a research topic. Over the lifetime, 779 publications have been published within this topic receiving 9242 citations.

A fast numerical method for calculating propeller aerodynamic and acoustic characteristics

Abstract: This paper deals with a fast numerical method for calculating propeller aerodynamic and acoustic characteristics.The traditional vortex lattice method puts vortexes of unknown strength on blade surface,which can calculate total thrust and torque coefficients of propeller.Because of ignoring the effects of dipoles,it can not calculate surface pressure distribution.A new lift surface technique,which was proposed by the authors first,distributes vortexes of unknown strength density on blade surface and makes better results of pressure distribution.Based on these pressure distribution and Farassats solution of FW-H equation,the sound pressure lever of low speed propeller can be calculated in a few minutes with fair agreement with experiments.

Simulation of a High Disc Loading Free Propeller in a Cross Flow by the Vortex-Lattice Method

Abstract: : A study was conducted to develop an analytical model for the investigation of flow fields about intermediate disc loading lift devices for VTOL applications Classical vortex-lattice theory was used in conjunction with experimental data for representing a free propeller in a crossflow The jet phenomena to be simulated by the method are discussed A number of previous attempts at vortex-lattice modeling are presented Analytical stream lines and field vectors are compared with available experimental data The results are evaluated and recommendations are made for further model development

Coupling a Numerical Optimization Technique with a Panel Method or a Vortex Lattice Method to Design Cavitating Propellers in Non-Uniform Inflows

Abstract: In this study, a nonlinear optimization method, which is coupled with either a panel method or a vortex lattice method, is used to design open propellers in uniform, circumferentially averaged or non-uniform inflow. A B-spline geometry with 4× 4 control points is used to ensure that the propeller blade is accurately defined with fewer parameters. The optimization objective is to maximize the efficiency of the propeller while satisfying the given propeller thrust, and different cavity area or pressure constraints are applied. The influence of those constraints are studied, and propeller geometries are designed in different cases. The optimal efficiency as a function of the thrust coefficients are compared with those from other references, and the optimal circulations from this method are compared with those predicted from the lifting line optimization theory. It is shown that this method satisfies the optimization objectives and can be used in the practice of designing cavitating propellers. Keyword: optimization; panel method; vortex lattice method; cavitating propeller design Introduction The preliminary design of marine propellers has been gradually developing in the past. Generally, the methods used can be categorized into two types [Kerwin and Hadler, 2010]. The first one involves using systematic series of propellers, whose open water characteristics are already known, either from experimental tests or from computational fluid dynamic simulations [Yeo et al., 2014]. A widely seen example is by using the Wageningen B-screw series [van Lammeren et al., 1969]. The second type of methods do not require and are not limited to the known propeller series, but are based on the optimal radial distribution of circulation. These methods need the circumferentially averaged inflow, and are more adapted to the nominal wake filed downstream of the ship hull. An alternative approach can be seen as an improvement of the second type of methods. Mishima and Kinnas [1997] developed a numerical optimization method which is coupled with a Vortex Lattice Method (VLM) to design the cavitating propellers in the non-uniform inflow. A major advantage of this method is that it considers the circumferential variance of the inflow, which is important in predicting the periodic pressure fluctuations and the vibrations on the ship hull caused by the propeller in unsteady non-axisymmetric inflows. This method uses a B-spline to represent the blade geometry, and the optimization objective and constraints (thrust, torque, cavitation area, etc.) are approximated via second-order Taylor expansions. This method allows a constrained amount of cavitation in the design and thus can be applied to design propellers working under a moderate or even high loading. A numerical code called CAVOPT-3D (3-Dimensional CAVitating propeller blade OPTimizaiton) was developed and later improved by Griffin and Kinnas [1998] to include the minimum pressure constraints and a one-variable quadratic skew optimization. In the Ocean Engineering Group of University of Texas at Austin, the prediction of flows around propellers has been studied intensively in the past decades. The two major codes are MPUF-3A, which uses the VLM, and PROPCAV (PROPeller CAVitation), which uses the Boundary Element Method (BEM, more commonly known as the panel method). Some major improvements in MPUF-3A include: the thickness loading coupling scheme by Kinnas [1992], the unsteady wake alignment scheme and the non-linear terms in pressure evaluation by He [2010], etc. In PROPCAV, Kinnas et al. [2007] coupled the panel method with a boundary layer solver XFOIL [Drela, 1989] and developed the viscous/inviscid interaction method; Tian and Kinnas [2012] introduced a pseudo-unsteady wake alignment scheme ∗Corresponding Author, Weikang Du: allendu1988@utexas.edu (full wake alignment scheme, or FWA) to improve the accuracy of the predicted propeller performances, especially at low advance ratios. In this paper, the nonlinear optimization method is coupled with the newest version of MPUF-3A and PROPCAV to design cavitating propellers. Different constraints will be applied, and various inflows, including uniform, circumferentially averaged and non-uniform inflow will be used. The efficiency and optimal circulation from the current method will be compared with those from other references [Kerwin and Hadler, 2010] or the lifting line optimization method [Menéndez Arán and Kinnas, 2014].

A study of the unsteady aerodynamics of a wing at high angles of attack using decambering to model separated flow

Abstract: An Unsteady Vortex Lattice Method is developed and validated. It is coupled with a decambering methodology to account for viscous effects on the aerodynamic coefficients. Two additional methodologies to select a unique solution when multiple solutions arise have been proposed. The transient nature of the aerodynamic loads of a suddenly moving wing at different angles of attack is examined. Sudden jumps are observed in the $$C_L(t)$$ at post-stall angles of attack. The jumps are followed by the presence of asymmetric solutions, which then decline with time and a change in the solution state. Higher angles of attack see an increasing number of jumps.

Development and Analysis of Variable Pitch Propeller with Aerodynamic Stable Blades

Abstract: For small short/vertical takeoff and landing (S/VTOL) unmanned aerial vehicles, the propeller design should reach a compromise between S/VTOL and cruise. But the complexity cost of a variable-pitch...