Investigation of the Unsteady Behavior of a Circulation Control Wing Using Computational Fluid Dynamics

Abstract

This paper details the results of an investigation into the unsteady behavior of a circulation control wing using computational fluid dynamics. Oscillations in the lift coefficient of up to 10% are observed for steady state simulations. An investigation into the source of the unsteadiness is underway, and the results to date are presented. It is shown that the periodic oscillations are independent of the above the wing mounted engine effects on the cruise efficient short takeoff and landing aircraft. The oscillations are also a viscous phenomenon that does not dampen as the solution marches through steady state. It is proposed that the cause of the oscillations is due to high streamline curvature at the trailing edge inboard wing section, due to flow turning caused by the slot flow normal condition at the circulation control slots. This paper presents the results into the origin of this unsteadiness.

Development of a laminar boundary layer model for curved wall jets

“…As discussed in Ref [1][2][3], the current computational fluid dynamics methods have often proven to be inexact. Even the purpose tailored RANS models such as the Spalart-Almaras with Rotation and Curvature correction Ref [4] or the Menter SST RC Ref [5,6] were shown to have only limited success in describing the radial velocity distribution for thin Coandă jets [7,8].…”

A New Mathematical Model for Coandă Effect Velocity Approximation

“…This does not influence the applicability of the model since most wings that use the Coandă effect both Upper Surface Blown Wings Ref [25] and entrainment wings [26] maintain the jet attached on a section ranging from 80° to 110°.…”

Implementation of a correction factor for the Pohlhausen laminar boundary layer applied on the CEVA curved wall jet model

“…Applications of curved wall jets -subject to the Coandă effect -have long been implemented in the aeronautical industry in obtaining higher lift -such as the USB Refs [1][2][3] Fig.1 a. or entrainment Refs [4][5][6][7] Fig.1 b. wings, or replacing the wing altogether Refs [8,9] Fig.1 c; other applications refer to replacing stability control devices such as the helicopter tail rotor with a Coandă-effect curved wall jet on the rotorcraft tail boom Ref [10][11] Fig. 1 Although analytical models were developed for estimating the flow fields over curved surfaces Ref [12], or dedicated turbulence models which compensate for wall curvature Ref [13] or [14], the semi-empirical models such as the ones described by Lewinsky and Yeh [15] or Seed [16] still offer the advantage of being experimentally validated in their design range.…”