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.

On Boeing 737 – 300 Wing Aerodynamics Calculations Based on VLM Theory

Abstract: In this paper, aerodynamics coefficients of Boeing 737 - 300 are calculated using VLM (vortex lattice method) theory. The wing was divided into panels of the size: 6X6. The wing was assumed to be planar and the panels are in the trapezoid shape. Aerodynamics lifting and moment coefficients were calculated. Also, center of pressure location was found using data from VLM and wing geometry. Comparisons between literature, finite wing theory and VLM theory were done. It was found that maximum lifting coefficient error between literature and VLM is about 4.0%. Moreover, the maximum lifting coefficient error between finite wing theory and VLM is about 2.2%. Center of pressure location error between finite wing theory and VLM is about 0.5%.

Analysis of wake surfing benefits using a fast unsteady vortex lattice method

Abstract: The computer simulation framework Flexit is used to analyse the fuel economy benefit of aircraft wake surfing. Wake surfing involves multiple aircraft flying in close formation during cruise conditions to reduce overall induced drag and improve overall fuel efficiency. The aircraft fly in echelon such that the kinetic energy lost in vortices generated by the lead aircraft can be partially recovered by the following aircraft flying in regions of the wake where induced velocities have an upwardly directed vertical component. We build on recent theoretical and flight test work by developing a medium fidelity methodology using Flexit for predicting potential performance benefits of wake surfing. We present results from a specific systematic parametric study that corresponds to a series of recent flight tests with two C-17 transport aircraft to demonstrate the methodology and predict the fuel savings that can be obtained by different arrangements of aircraft in a wake surfing formation. The predictions are compared with the flight test data and the trends observed in our simulations agree with the trends of the full scale tests.

A Calculation Method for Over-the-Wing Engines within Conceptual Aircraft Design

Abstract: In this paper, a physics-based computationally inexpensive model is developed to predict aircraft performance variation due to over-the-wing engine installation effects in terms of lift, drag and structure weight at the conceptual stage of aircraft design. The aerodynamic influence caused by the installation of the engine is calculated at cruise conditions using a vortex lattice method. The structural wing weight is calculated iteratively by means of inner loads considering aerodynamic loads, inertial loads and engine thrust. After a parameter study, formulas which can be used to take into account the position of over-the-wing engines during conceptual aircraft design are developed.

Aerodynamic analysis for control and simulation of unmanned aerial vehicles

Abstract: This research project is focused on the aerodynamic modeling of unmanned aerial vehicles (UAV) and its application to determine the aircraft aerodynamic characteristics. The aerodynamic modeling procedure of the UAV is based on the vortex lattice method (VLM). The goal is the computation of the aerodynamic stability and control derivatives for composing the flight vehicle equations of motion. The vortex lattice method code that will be used is the Tornado VLM Toolkit, a MATLAB based freeware program developed at KTH- Sweden. The aerodynamic (stability) derivatives shall be validated by comparing the calculated derivatives with the corresponding aerodynamic derivatives identified from experimental flight data. The unmanned aerial vehicles that is used for this research is called Vector-P. During the flight several maneuvers have been done to retrieve good data. The maneuvers that were done are the doublet and the 3-2-1-1 maneuver. By doing four identifications and one validation the longitudinal aerodynamic derivatives of the Vector-P are determined. Next the results of the flight testing are compared with the result of Tornado. Unfortunately only one derivative is more or less the same with both methods. The difference in the aerodynamic coefficients will have a great influence on the fly performance of the Vector-P. In Matlab a manoeuvre was simulated with both coefficients. The two manoeuvres were very different from each other and the velocity in both cases was not a match either. The main reason is that the Cmα is calculated too high by Tornado.

Prediction of Steady Performance of Contra-Rotating Propellers Including Wake Alignment

Abstract: To reduce fuel oil costs and emission of greenhouse gases of ships in operation, application of Contra-Rotating Propellers (CRP) will be one of the solutions, which have high propulsive efficiency. Although several estimation methods of predicting open water characteristics of CRP have been developed in the past, few methods treat accurately with trailing wake geometry, which influences much on estimate accuracy. CRP makes the flow around the propellers more complicated compared with conventional single propeller because aft and forward propeller of CRP interacts each other strongly. In order to improve estimate accuracy, more rigorous treatment of the trailing wake geometry is desirable. This paper presents a calculation method, taking deformation of trailing wake accurately into account. The method is based on a simplified surface panel method "SQCM" which satisfies the Kutta condition easily. The SQCM consists of Hess and Smith type source panels on the propeller surface and discrete vortices on the camber surface according to Lan's QCM (Quasi-Continuous vortex lattice Method). The wake vortex lines are arranged in accordance with the direction of the flow including induced velocity by both propellers. The authors show some calculated results and validate them by comparing experiments in this paper. It is found that thrust and torque of the aft propeller differ considerably depending on which the deformation of trailing wake is taken into account or not. The calculated results with deformed wake agrees very well with the experiment, while the calculated results without deformed wake always overestimate the thrust and torque of the aft propeller.