Jixian Yao _ Research Activities

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My Research Activities on Turbomachinery CFD

Recent Research Activities
Achievements
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Recent Research Activities

(1)TFLO
As a research staff associated to Prof. Antony Jameson, I am currently working on ASCI Project at Stanford University to develop the code TFLO. TFLO is a massively parallel flow solver which uses techniques including a modified Runge-Kutta scheme, the JST scheme and the CUSP scheme, dual-time stepping for time accurate calculations, general multi-block structured meshes, acceleration of multi-grid and implicit residual smoothing, and MPI parallelization. Turbulence models includes Baldwin-Lomax model, Spalart-Allmaras model, Wilcox k-omega model.

(2)TURBO90
TURBO90 has been developed for the turbomachinery flow calculation by Prof. Feng Liu at University of California, Irvine and Prof. Antony Jameson. I had been working on this code for about two years at University of California, Irvine, for the collorbration with the code STAGE3D developed by ABB(Baden,Switzerland).

Achievements

(1) Basics
Four principal high-resolution schemes (Yee-Harten, Osher-Chakravarthy, J.Y.Yang, and NND) are compared and calibrated for their application.Based on the uniformly third-order accurate nonoscillatory scheme (UNO3) and modified lower-upper symmetric Gauss-Seidel (LU-SGS), the three-dimensional Reynolds-averaged Navier-Stokes equations are solved by the use of Baldwin-Lomax turbulence model.

(2) Isolated Blade Row
A computer code for steady calculation of isolated blade row has been developed and validated by Rotor-37 issued by NASA, a blind test presented in Hague, 1994.

(3) Multistage Environment - Steady Flows
A computer code for steady calculation of multistage environment has been established by introducing the mixing plane for flow variables exchange. Circumferential mass averaging procedure is employed but maintain the spanwise variation.

(4) Multistage Environment - Rotor/Stator Interaction
A computer code for true unsteady rotor-stator inter interaction calculation has been implemented recently by the use of overlapped grid on interfaces. The case for one rotor to one stator of one stage has already been finished and validated. The case for m-rotor to n-stator of one stage has also been developed. Test examples show that the code works robust, the accuracy is satisfactory. The one-stage unsteady code has also been modified to simulate the unsteady flows in a centrifugal compressor, include a impeller and a diffuser. The comparison shows that the experiment and time-averaged calculation results agree well. The experiment data is from T. Nagashima of University of Tokoyo.

(5) The Controlling of Three-Dimensional Shock Structure
On the support of the tools, the skewed-swept blades are studied. And the organizing and controlling of three-dimensional shock in rotor blade row has been studied. The calculation can simulate all the exist shock structure provided by experimetal measurements. Swept back blade can reduce shock loss hence improve the efficiency of the rotor, but efforts towards careful re-design of rotor blade must be made to ensure the enough margin of stability.

(6) Three-Dimensional Unstructured Grid
The work conducting now is on three-dimensional unstructured grid and solver for turbomachinery flows. Now, a 2D grid generation code and a 3D grid generation code and a Euler solver for flows around a solid body grid is available.