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.

Computational analysis of low mass moment of inertia flying wing

Abstract: The primary goal in development of MAVs is to develop a flying body that weigh as less as 90 grams, with a span of 15cm [1]. Since it is challenging to meet these design characteristics of a MAVs with current technology, there has been a lot of research going on in this direction. This paper is also a continuation of the same quest. In this research a delta wing micro air vehicle was analyzed at low sub sonic speed at different angles of attack for determining lift, drag force, stall angle and L/D ratio. CFD and XFLR have been used as computational tools. For CFD analysis, a far field technique was used to calculate the lift and drag coefficients. Rectangular domain was created around the body with a size 10 times greater than body so that flow behavior can be captured accurately. Inflation layers were created around the body to capture boundary layer. Fine mesh was created at the regions of higher gradients. In fluent flow was analyzed using two turbulent models (SA and k-e). A potential flow solver (XFLR) was also used to compare results from RANS methodology with vortex lattice method (VLM). Validation of computational results was carried out by comparing with earlier research concerning wind tunnel testing of MAV [2] at 100,000 Re. This research will help the aero dynamists to understand the complete procedure of computational and XFLR analysis of MAVs. It was found that XFLR predicts higher values of lift coefficient and lower values of drag coefficient at all angles of attack. Consequently, lift to drag ratio as predicted by XFLR was found greater than RANS models. Further no appreciable difference was noticed between lift and drag characteristics predicted by SA and k-e models.

TRW vortex-lattice method subsonic aerodynamic analysis for multiple-lifting-surfaces (N. surface) TRW program number HA010B

Abstract: The program was designed to provide solutions of engineering accuracy for determining the aerodynamic loads on single- or multiple-lifting-surface configurations that represent vehicles in subsonic flight, e.g., wings, wing-tail, wing-canard, lifting bodies, etc. The preparation is described of the input data, associated input arrangement, and the output format for the program data, including specification of the various operational details of the program such as array sizes, tape numbers utilized, and program dumps. A full description of the underlying theory used in the program development and a review of the program qualification tests are included.

Evaluation of Formation Flights with Long Range Aircraft for Different Flight Conditions and Atmospheric Disturbances

Abstract: The aerodynamic formation flight, which is also called air wake surfing for efficiency (AWSE), can lead to a high drag reduction at the trailing aircraft of more than ten percent resulting in a reduced fuel burn. Therefore, this operational strategy represents a promising means to reduce the greenhouse effect of aviation. The following study investigates the flight of two long haul commercial aircraft in an echelon formation in a stationary state, a flight dynamic simulation and finally at trajectory level. Thereby, the effect of different cruise altitudes and speeds, aircraft masses, lateral and vertical separations and different intensities of gusts and turbulence are evaluated. Based on the aircraft data set from the in house preliminary aircraft design tool MICADO a vortex lattice method calculates the induced loads in the trailing wake behind the leader. Subsequently, the results are used in the flight simulation program to analyze the flight behavior of the trailing aircraft in the formation under the influence of atmospheric disturbances. Finally, the results of the vortex lattice method and the flight simulation provide the necessary input data for the evaluation of the benefits achievable during the entire mission based on a detailed trajectory calculation. High altitudes and low Mach numbers during the formation flight lead to the highest drag reductions at the trailing aircraft. Movements of the trailing aircraft away from the optimum location in the vortex of the leading aircraft and additional detours lead to reduced fuel savings of ten percent or less.

A small aircraft in hazardous wake near ground using unsteady vortex lattice method

Abstract: The interaction between small aircraft and vortex system generated by another much larger aircraft is investigated. An aerodynamic model based on the modified unsteady vortex lattice method and the method of images was developed. A simple wake model can be developed using this vortex system. The large aircraft represented by a large wing, while, the small aircraft represented by a small wing, were used in this study. Investigation was done for the small aircraft, as it is entering and flying parallel to the wake left by the larger aircraft near ground, during aircraft landing operation, with all aerodynamic surfaces assumed to be of zero thickness. The lateral position of the small wing with respect to the large wing center line is assumed to be variable. Changes in lift, drag, pitching moment and rolling moment coefficients, for the small aircraft, are calculated and presented for deferent cases of study. A case study shows that, as the small aircraft enters the wake left by a large aircraft, a sudden decrease in aerodynamic forces and moments takes place. This situation is more noticeable and dangerous near ground as the small aircraft approaching the ground during landing or take off operations. The lateral position of the small aircraft with respect to the larger one has a great effect, where the lift force could become unsymmetric on both sides of the small wing. This could put the small aircraft into a rolling motion, where it could be deviated from its flight path during the landing or take off operations, an accident might be the result.

Generalized vortex lattice method for oscillating lifting surfaces in planar supersonic flow

Abstract: The velocity potential formulation is used to study the behavior of lifting surfaces oscillating harmonically in supersonic flow. Here the basic singularity is a doublet of constant density, corresponding to quadrilateral panels distributed over the wing and wake. The advantage of the present method over others available in the literature is the unification of the solution for the subsonic and supersonic regimes. Steady-state results are presented for both rectangular and delta wings, and they compare very well with analytical results when the wing aspect ratio is varied. Unsteady results along the symmetry line for a pitching rectangular wing are also presented, and again the agreement is excellent with bidimensional values. Finally, generalized aerodynamic coefficients are calculated and compared with several results available in the literature.