A suite of five computational fluid dynamics (CFD) codes has been developed for analysis of flows in turbomachinery. Two of the codes are used to generate two-dimensional (2-D) or three-dimensional (3-D) grids that describe the turbomachinery blade geometry. The other three codes solve the Navier-Stokes equations on those grids to predict the performance of the blades. Three mathematical models of turbulence that include effects of flow transition and roughness are available. The codes are applicable to fans, compressors, and turbines in both axial and radial machines.

The codes include the following:

  • GRAPE (Grids About Airfoils Using Poisson'sEquation) generates a two-dimensional blade-to-blade periodic grid. GRAPE is used with RVCQ3D, which is described next.
  • RVCQ3D (Rotor Viscous Code Quasi-3-D) is a code for quasi-3-D blade-to-blade analysis that includes the effects of rotation, change of radius, and variable stream surface thickness.
  • TCGRID (Turbomachinery C-Grid) generates a 3-D grid used with RVC3D and SWIFT, which are described next.
  • RVC3D (Rotor Viscous Code 3-D) is a code for 3-D analysis of isolated blade rows.
  • SWIFT is a code for 3-D, multiblock analysis that affords grid capabilities additional to those of RVC3D, including the ability to model tip-clearance flows and multistage turbomachinery.
Figure 1. These Mach-Number Contours were computed for transonic flow around turbine vanes.

The codes can be used independently but often are used in sequence. RVCQ3D is used to investigate many design parameters quickly in two dimensions, RVC3D is used to predict the performance of isolated blade rows, and SWIFT is used to study a 3-D blade in more detail or in a multistage environment.

RVCQ3D, RVC3D, and SWIFT solve finite-difference approximations of equations of flow by use of an explicit Runge-Kutta scheme. A spatially variable time step and implicit residual smoothing are used to accelerate convergence. Preconditioning can also be performed for low-speed (incompressible) flows.

The codes have been verified with respect to transonic flow around turbine vanes (see Figure 1) and with respect to a transonic compressor stage (see Figure 2). They have also been used to analyze many fan blades, the fuel turbine for the space shuttle main engine, wind-tunnel turning vanes, centrifugal compressors, and a vacuum-cleaner impeller.

Figure 2. These Pressure Contours were computed for a transonic compressor stage.

The codes are written in Fortran and can be compiled and run on most computers. Blade data are entered by use of a common Glenn Research Center design-code format. Simple namelist input is used for flow parameters. Some printed output is generated. No graphical output is provided, but grid and solution files are in a standard format that can be read directly by most CFD visualization software packages, including FAST and PLOT3D.

This work was done by Rod Chima of Glenn Research Center. Details about the individual codes and sample results may be found on the author's web site, www.grc.nasa.gov/WWW/5810/webpage/rvc.htm.

LEW-16851


NASA Tech Briefs Magazine

This article first appeared in the November, 1999 issue of NASA Tech Briefs Magazine.

Read more articles from the archives here.