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HIGHER-ORDER ACCURATE SOLUTION FOR FLOW THROUGH A TURBINE LINEAR CASCADE

AYYALASOMAYAJULA, HARITHA
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1054757181

Abstract Details

2003, MS, University of Cincinnati, Engineering : Mechanical Engineering.
Low-pressure turbines (LPT) in aircraft engines undergo tremendous losses at cruise conditions. The flow Reynolds number at cruise is lower than the take-off Reynolds number by a factor of almost two. At low Reynolds numbers, the flow is largely laminar, and tends to separate easily on the suction surface of the turbine blade when an adverse pressure gradient is encountered. Therefore, accurate prediction of flow separation is crucial for an effective design of LPT blade; and is achieved in the present work using a high-order accurate numerical solution procedure. The three-dimensional, unsteady, full Navier-Stokes equations are solved to analyze the flow. A MPI-based higher-order, parallel, chimera version of the FDL3DI flow solver, is extended for use with this turbomachinery application. A sixth-order accurate compact-difference scheme is used for the spatial discretization, along with second-order accurate temporal discretization. Tenth-order filtering is used to minimize the numerical oscillations in the flow solution and maintain numerical stability. The objective of the present study is to show the ability of higher-order accurate compact-difference scheme to predict the flow separation that occurs inside an LPT cascade at Re C = 25,000 (based on axial chord and inlet velocity). A new set of subsonic inflow/outflow boundary conditions that account for upstream influence (BC2) are derived by specifying stagnation quantities at the inlet, and a static quantity at the exit of the flow domain, and maintaining the inflow angle constant. For inflow/outflow boundary conditions that do not account for upstream influence, fixed inflow with extrapolated outflow (BC1) has been utilized. The effect of the two different sets of inflow/outflow boundary conditions on the flow solution is studied, for second-order, fourth-order and sixth-order accurate schemes. The computed Cp distribution for the LPT flow shows good agreement with the existing experimental data. The location of the onset of separation matches with an available LES simulation result and with the available experimental data. The performance of high-order compact difference schemes has been assessed via simulation of laminar flow over a circular cylinder at Re D = 250 (based on free-stream velocity and cylinder diameter). The sixth-order accurate compact difference scheme with tenth-order filtering on a coarser mesh preserves the vortex structure better than possible with the second-order accurate scheme on a finer mesh. This demonstrates the efficiency of the higher-order accurate compact difference scheme.
Dr. Urmila Ghia (Advisor)
144 p.
Engineering, Mechanical
low-pressure turbine; high-order accurate method; filtering; flow separation; Navier-stokes equations

Recommended Citations

Citations

  • AYYALASOMAYAJULA, H. (2003). HIGHER-ORDER ACCURATE SOLUTION FOR FLOW THROUGH A TURBINE LINEAR CASCADE [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1054757181

    APA Style (7th edition)

  • AYYALASOMAYAJULA, HARITHA. HIGHER-ORDER ACCURATE SOLUTION FOR FLOW THROUGH A TURBINE LINEAR CASCADE. 2003. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1054757181.

    MLA Style (8th edition)

  • AYYALASOMAYAJULA, HARITHA. "HIGHER-ORDER ACCURATE SOLUTION FOR FLOW THROUGH A TURBINE LINEAR CASCADE." Master's thesis, University of Cincinnati, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1054757181

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Cincinnati and OhioLINK.