Three-dimensional viscous flow simulations in a turbine stator using a nonperiodic H-type grid

The effects of circumferential distortions in inlet total pressure on the flow field in a low-aspect-ratio, high-speed, high-pressure-ratio, transonic compressor rotor are investigated in this paper. The flow field was studied experimentally and numerically with and without inlet total pressure distortion. Total pressure distortion was created by screens mounted upstream from the rotor inlet. Circumferential distortions of 8 periods per revolution were investigated at two different rotor speeds. The unsteady blade surface pressures were measured with miniature pressure transducers mounted in the blade. The flow fields with and without inlet total pressure distortion were analyzed numerically by solving steady and unsteady forms of the Reynolds-averaged Navier-Stokes equations. Steady three-dimensional viscous flow calculations were performed for the flow without inlet distortion while unsteady three-dimensional viscous flow calculations were used for the flow with inlet distortion. For the time-accurate calculation, circumferential and radial variations of the inlet total pressure were used as a time-dependent inflow boundary condition. A second-order implicit scheme was used for the time integration. The experimental measurements and the numerical analysis are highly complementary for this study because of the extreme complexity of the flow field. The current investigation shows that inlet flow distortions travel through the rotor blade passage and are convected into the following stator. At a high rotor speed where the flow is transonic, the passage shock was found to oscillate by as much as 20% of the blade chord, and very strong interactions between the unsteady passage shock and the blade boundary layer were observed. This interaction increases the effective blockage of the passage, resulting in an increased aerodynamic loss and a reduced stall margin. The strong interaction between the passage shock and the blade boundary layer increases the peak aerodynamic loss by about one percent.

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Three dimensional flow simulations with the finite element technique over a multi-stage rocket

10.2514/6.2002-408 ◽

2002 ◽

Cited By ~ 4

Author(s):

L. Scalabrin ◽

J. Azevedo ◽

P. Teixeira ◽

A. Awruch

Keyword(s):

Finite Element ◽

Three Dimensional ◽

Three Dimensional Flow ◽

Finite Element Technique ◽

Flow Simulations ◽

Dimensional Flow ◽

Multi Stage ◽

Element Technique

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Reducing Undesired Wave Reflection at Domain Boundaries in 3D Finite Volume-Based Flow Simulations via Forcing Zones

Journal of Ship Research ◽

10.5957/jsr.2020.64.1.23 ◽

2020 ◽

Vol 64 (01) ◽

pp. 23-47

Author(s):

Robinson Peric ◽

Moustafa Abdel-Maksoud

Keyword(s):

Finite Volume ◽

Wave Reflection ◽

Three Dimensional ◽

Navier Stokes ◽

Special Focus ◽

Computational Domain ◽

Wave Reflections ◽

Flow Simulations ◽

Large Eddy ◽

Domain Boundaries

This article reviews different types of forcing zones (sponge layers, damping zones, relaxation zones, etc.) as used in finite volume-based flow simulations to reduce undesired wave reflections at domain boundaries, with special focus on the case of strongly reflecting bodies subjected to long-crested incidence waves. Limitations and possible sources of errors are discussed. A novel forcing-zone arrangement is presented and validated via three-dimensional (3D) flow simulations. Furthermore, a recently published theory for predicting the forcing-zone behavior was investigated with regard to its relevance for practical 3D hydrodynamics problems. It was found that the theory can be used to optimally tune the case-dependent parameters of the forcing zones before running the simulations. 1. Introduction Wave reflections at the boundaries of the computational domain can cause significant errors in flow simulations, and must therefore be reduced. In contrast to boundary element codes, where much progress in this respect has been made decades ago (see e.g., Clement 1996; Grilli &Horillo 1997), for finite volume-based flow solvers, there are many unresolved questions, especially:How to reliably reduce reflections and disturbances from the domain boundaries?How to predict the amount of undesired wave reflection before running the simulation? This work aims to provide further insight to these questions for flow simulations based on Navier-Stokes-type equations (Reynolds-averaged Navier-Stokes, Euler equations, Large Eddy Simulations, etc.), when using forcing zones to reduce undesired reflections. The term "forcing zones" is used here to describe approaches that gradually force the solution in the vicinity of the boundary towards some reference solution, as described in Section 2; some examples are absorbing layers, sponge layers, damping zones, relaxation zones, or the Euler overlay method (Mayer et al. 1998; Park et al. 1999; Chen et al. 2006; Choi &Yoon 2009; Jacobsen et al. 2012; Kimet al. 2012; Schmitt & Elsaesser 2015; Perić & Abdel-Maksoud 2016a; Vukčević et al. 2016).

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Development of a Three-Dimensional Geometry Optimization Method for Turbomachinery Applications

International Journal of Rotating Machinery ◽

10.1155/s1023621x04000387 ◽

2004 ◽

Vol 10 (5) ◽

pp. 373-385

Author(s):

Steffen Kämmerer ◽

Jürgen F. Mayer ◽

Heinz Stetter ◽

Meinhard Paffrath ◽

Utz Wever ◽

...

Keyword(s):

Optimization Problem ◽

Stokes Equations ◽

Turbine Blades ◽

Three Dimensional ◽

Optimization Techniques ◽

Navier Stokes ◽

Physical Parameters ◽

Flow Solver ◽

Flow Simulations ◽

Sensitivity Equations

This article describes the development of a method for optimization of the geometry of three-dimensional turbine blades within a stage configuration. The method is based on flow simulations and gradient-based optimization techniques. This approach uses the fully parameterized blade geometry as variables for the optimization problem. Physical parameters such as stagger angle, stacking line, and chord length are part of the model. Constraints guarantee the requirements for cooling, casting, and machining of the blades.The fluid physics of the turbomachine and hence the objective function of the optimization problem are calculated by means of a three-dimensional Navier-Stokes solver especially designed for turbomachinery applications. The gradients required for the optimization algorithm are computed by numerically solving the sensitivity equations. Therefore, the explicitly differentiated Navier-Stokes equations are incorporated into the numerical method of the flow solver, enabling the computation of the sensitivity equations with the same numerical scheme as used for the flow field solution.This article introduces the components of the fully automated optimization loop and their interactions. Furthermore, the sensitivity equation method is discussed and several aspects of the implementation into a flow solver are presented. Flow simulations and sensitivity calculations are presented for different test cases and parameters. The validation of the computed sensitivities is performed by means of finite differences.

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Factors Affecting Measured Axial Compressor Tip Clearance Vortex Circulation

Journal of Turbomachinery ◽

10.1115/1.2835685 ◽

1995 ◽

Vol 117 (3) ◽

pp. 487-490 ◽

Cited By ~ 1

Author(s):

S. A. Khalid

Keyword(s):

Viscous Flow ◽

Three Dimensional ◽

Axial Compressor ◽

Tip Clearance ◽

Radial Transport ◽

Factors Affecting ◽

Blade Tip ◽

Tip Clearance Vortex ◽

The Relationship ◽

Principal Contributor

The relationship between turbomachinery blade circulation and tip clearance vortex circulation measured experimentally is examined using three-dimensional viscous flow computations. It is shown that the clearance vortex circulation one would measure is dependent on the placement of the fluid contour around which the circulation measurement is taken. Radial transport of vorticity results in the magnitude of the measured clearance vortex circulation generally being less than the blade circulation. For compressors, radial transport of vorticity shed from the blade tip in proximity to the endwall is the principal contributor to the discrepancy between the measured vortex circulation and blade circulation. Further, diffusion of vorticity shed at the blade tip toward the endwall makes it impossible in most practical cases to construct a fluid contour around the vortex that encloses all, and only, the vorticity shed from the blade tip. One should thus not expect agreement between measured tip clearance vortex circulation and circulation around the blade.

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