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.

Unsteady forces on counter-rotating propeller blades

Abstract: Unsteady forces experienced by counter-rotating propeller blades are examined in this paper. A fully coupled vortex lattice model of counter-rotation is used to obtain a quasi-steady solution to the propeller loadings, and an unsteady Sears (1941) analysis provides an estimate of the unsteady loads from the quasi-steady results. The vortex lattice method predicts the overall performance of counter-rotation well, based on comparisons of measured and predicted results. The effects of propeller spacing and blade number on the unsteady loadings are investigated. The peak-to-peak variation about the mean of the unsteady loads on the rear propeller varied from 9 percent for a 2 x 2 counter-rotation system to 2 percent for an 8 x 8 system.

Steady state aerodynamic analysis of aeroplane wings with constant and varying cross section

Abstract: This paper presents a FORTRAN program for estimating aerodynamic characteristics of a wing planform of constant and varying cross-section of an aeroplane using Vortex Lattice Method (VLM). The Aerodynamic characteristics of interest are Lift, Drag acting on different parts of the wing. The program was developed to understand the effect of various parameters such as Aspect Ratio (AR), Sweep Back angle, Vortex or Panel formation and ground proximity on Lift and Drag and also to decide the wing dimensions for different wing configurations under Steady Subsonic flow. The results were obtained for a wing planform with rectangular Cross section with a specified Aspect Ratio. The theoretical results for Lift, Drag are computed using VLM. The obtained theoretical results are compared with the experimental results.

Numerical Simulation of Rowing Sculls at Large Angle of Attack

Abstract: In this paper, the unsteady nonlinear vortex lattice method is used to calculate hydrodynamic performance of the thin wing. Plane quadrilateral vortex lattices are used to approximate the body surface. The vortex strengths on the body and free vortex are solved by iteration alternately. The paper establishes an iteration scheme of rapid convergence, i. e., the vortex strength and free vortex location converge at the same error order. The converged solution of small aspect radio thin wing at large attack angle is also very quickly obtained. The hydrodynamic forces acting on thin wing in some depts of water are calculated by image method. The steady and unsteady hydrodynamic forces on several rectangular flat plates and circle wings with aspect ratios as small as 0.2, at attack angles as large as 60° and in some water depths are calculated. The agreement between present numerical results of these airfoils and experimental results or other calculatons indicates that the present work is successful. The rowing scull is a kind of thin wing (0.5λ1.2). It always works at large attack angles near 90°. In this paper, the steady and unsteady hydrodynamic performance of "Big Blade", which is most used in the rowing competition, is calculated. The dependence of some energetics on the concerned physical parameters, such as the depth of water, the frequency,etc., is exhibited. Based on these calculation, the technique in rowing sports in the viewpoint of hydrodynamics is analyzed.

Unsteady Aerodynamic Coefficients Obtained by a Compressible Vortex Lattice Method

Abstract: Unsteady solutions for the aerodynamic coefficients of a thin airfoil in compressible subsonic or supersonic flows were studied. The lift, the pitch moment, and pressure coefficients were obtained numerically for the following motions: the indicial response (unit step function) of the profile, i.e., a sudden change in the angle of attack; a thin profile penetrating into a sharp edge gust (for several gust velocity ratios); a thin profile penetrating into a one-minus-cosine gust and sinusoidal gust, i.e., a typical gust used in commercial aircraft design; oscillating airfoil; and also the interaction of the profile with a convected (from convection phenomenon) vortex passing under the profile, a phenomenon known in literature as BVI (Blade Vortex Interaction) or for a profile case AVI (Airfoil Vortex Interaction). The present work uses a numerical approach based on vortex singularity. The numerical model was created through the profile discretization in uniform segments and the compressible flow vortex singularity was used. The results available in the literature are based on approximated exponential equations, or computed via Computational Fluid Dynamics (CFD). Thus, the purpose of this method is to obtain a more accurate computation compared to those of approximated equations, and quite faster than those done via CFD. The results yielded by the present methodology were also compared with solutions available in the literature. The results were obtained for subsonic and supersonic flow in compressible environment.