Development of a Steady Potential Solver for Use with Linearized Unsteady Aerodynamic Analyses

Abstract

A full potential steady flow solver (SFLOW) developed explicitly for use with an inviscid unsteady aerodynamic analysis (LINFLO) is described herein. The steady solver uses the nonconservative form of the nonlinear potential flow equations together with an implicit, least-squares, finite-difference approximation to solve for the steady flow field. The difference equations were developed on a composite mesh which consists of a C-grid embedded in a rectilinear (H-grid) cascade mesh. The composite mesh is capable of resolving blade-to-blade and far-field phenomena on the H-grid, while accurately resolving local phenomena on the C-grid. The resulting system of algebraic equations is arranged in matrix form using a sparse matrix package and solved by Newton's method.Steady and unsteady results are presented for two cascade configurations: a high-speed compressor and a turbine with high exit Mach number.

Combined-Simultaneous Gust and Oscillating Compressor Blade Unsteady Aerodynamics

“…Overall, the steady data agree well with SFLOW, a nonlinear potential code [10] and 1NCMCSCD, an incompressible inviscid small camber airfoil c 1 scade analysis [II], except near the leading edge. INCMCSCD predicts the correct maximum pressure difference location at low loading, but not at high loading.…”

Oscillating Cascade Aerodynamics at Large Mean Incidence

“…For a = 10°, solutions were not obtainable due to the extremely large flow gradients created by the sharp leading edge of the airfoils. The steady flow surface pressure distribution is correlated with the nonlinear full potential solver SFLOW (Hoyniak and Verdon, 1993), and the first harmonic surface pressure distribution is correlated with the linearized analysis LINFLO (Verdon and Hall, 1990). The predictions from SFLOW are used by LINFLO as the nonlinear background steady flow around which the harmonic unsteady flow solutions are formed.…”

Analysis of high Reynolds number inviscid/viscid interactions in cascades

“…The SFLOW analysis of Ref. [17] was modified to use the streamline H-mesh developed by Hall and Verdon [26]. Thus, prior to initiating an IVI calculation, an inviscid solution is obtained on a sheared H-mesh.…”

“…11 and was obtained by modifying the original blunt trailing-edge geometry to produce a wedge-shaped trailing edge while retaining the original chord length, as discussed in Ref. [17]. As for the cases discussed above, the mesh shown in the figure has fewer grid lines than were used in the actual calculation.…”

“…The steady, cascade, full-potential analysis (SFLOW) of Hoyniak and Verdon [17] is employed. SFLOW was constructed for use with the LINearized inviscid unsteady FLOw (LINFLO) analysis of Verdon and Caspar [14], to provide a comprehensive and compatible steady and unsteady inviscid flow prediction capability for cascades.…”